Theory and Technology for Improving High-Speed Railway Transportation Capacity 0323997007, 9780323997003

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THEORY AND TECHNOLOGY FOR IMPROVING HIGH-SPEED RAILWAY TRANSPORTATION CAPACITY

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THEORY AND TECHNOLOGY FOR IMPROVING HIGH-SPEED RAILWAY TRANSPORTATION CAPACITY

JUNFENG WANG State Key Laboratory of Rail Traffic Control and Safety, Beijing Jiaotong University, Beijing, China

BAOMING HAN School of Traffic and Transportation, Beijing Jiaotong University, Beijing, China

Elsevier Radarweg 29, PO Box 211, 1000 AE Amsterdam, Netherlands The Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, United Kingdom 50 Hampshire Street, 5th Floor, Cambridge, MA 02139, United States Copyright © 2023 Elsevier Inc. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permissions policies and our arrangements with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: www.elsevier.com/permissions. This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein). Notices Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary. Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility. To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein. ISBN: 978-0-323-99700-3 For information on all Elsevier publications visit our website at https://www.elsevier.com/books-and-journals

Publisher: Matthew Deans Acquisitions Editor: Jones Glyn Editorial Project Manager: Tom Mearns Production Project Manager: Anitha Sivaraj Cover Designer: Matthew Limbert Typeset by STRAIVE, India

Contents

Preface

ix

1. Background overview 1.1 Development course of transportation 1.2 Rail transit and transportation capacity 1.3 Improvement of line transportation capacity 1.4 Railway signaling transportation organization and line capacity References

1 4 8 11 20

2. High-speed railway signal technology and transport capacity 2.1 Train operation control system 2.2 Interlocking system 2.3 Dispatching command system References

23 41 47 54

3. Improving transport capacity by increasing the information amount of Chinese train control system 3.1 Expanding route information to improve transport capacity 3.2 Increase vehicle-to-ground transmission information to improve transport capacity 3.3 Improving transport capacity by applying intelligent technology References

57 75 91 106

4. Influence of variable approach locking section rules on station passing capacity 4.1 Improving station capacity by variable approach locking section rules 4.2 Optimizing operation of station 4.3 Integrated traffic management with station signal system References

v

109 123 127 143

vi

Contents

5. Optimize control method of train control system to shorten tracking interval 5.1 Adaptive dynamic coding for the track circuit in the CTCS-3 5.2 Train tracking interval optimization method 5.3 Optimization method of block section design References

147 160 177 187

6. Shorten the tracking interval through the control algorithm 6.1 CTCS-3I train control system with moving block function 6.2 CTCS-3I dynamic velocity curve algorithm 6.3 Optimization algorithm of CTCS-3I train movement authority 6.4 Vehicle–ground cooperation scheme in abnormal scenarios 6.5 Vehicle–ground cooperation scheme in abnormal scenarios References

189 199 212 222 222 223

7. Novel methods for improving transport capacity 7.1 Train-to-train communication 7.2 Cooperative control 7.3 Virtual coupling control system References

225 233 248 261

8. Influencing factors and calculation methods for carrying capacity of high-speed railway 8.1 Definition and characteristics of carrying capacity of high-speed railway 8.2 Calculation methods for carrying capacity of high-speed railways 8.3 Analysis on factors influencing carrying capacity of high-speed railway References

263 268 276 282

9. Mechanism of enhancing the carrying capacity of high-speed railway by precise headway in station 9.1 Concept and type of headway in station on high-speed railways 9.2 Existing calculation methods for headway in station 9.3 Precise calculation of headway in station based on time-space graph of train tracking operation References

283 285 289 358

Contents

vii

10. Principle of improving the carrying capacity of high-speed railway by adopting segmentation release mode 10.1 Overview of block section and train route 10.2 Overview of segmentation release mode 10.3 Calculation and adjustment of headway in station in segmentation release mode References

359 369 378 390

11. Methods for improving the carrying capacity of high-speed railway and examples 11.1 Existing methods for improving station carrying capacity 11.2 Model and algorithm for improving the carrying capacity of high-speed railway 11.3 Case study of application 11.4 Outlook References

Index

391 393 408 419 423

425

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Preface

Energy and environmental problems are increasingly prominent, and high-speed railway, as an efficient, energy-saving, and environmentally friendly mode of transportation, has been welcomed in many countries and regions in the world because of its advantages including high speed, large traffic volume, high punctuality rate, safety and comfort, allweather, low freight, low energy consumption, and being green and low carbon. Since the first high-speed railway, the Tokaido Shinkansen, began operation in Japan in 1964, high-speed railways have flourished around the world. At the time of writing, there are about 50,000 km of high-speed railway lines in operation in the world, and about 3 billion passengers take high-speed trains every year. In 2008, China opened its first high-speed railway, the Jing-Jin high-speed railway (Beijing to Tianjin). After that, the Zheng-Xi (Zhengzhou to Xi’an), Wu-Guang (Wuhan to Guangzhou), and Jing-Hu high-speed railways (Beijing to Shanghai) were successively opened, along with other high-speed railway lines. By 2021, the mileage of high-speed railway in operation was 40,000 km, with an average annual increase of 2857 km. China’s high-speed railway network has effectively taken shape, and China has entered the era of high-speed railways. On the one hand, from a global perspective, there is still room for improvement in the safety of both ordinary-speed and high-speed railways. In 2016, serious train collisions occurred in Munich (Germany), Puglia (Italy), New York (United States), Semnan Province (Iran), Multan (Pakistan), and many other countries. In the same year, numerous major train derailments also happened, including Pukhr€ayan (India), HuKun Railway (China), and Brooklyn (United States). A derailment and collision occurred on the China Jiaoji line on April 28, 2008, a rear-end collision accident happened on the China Yong-wen line on July 23, 2013, and a speeding train derailed in Spain 1 day later, on July 24. All of these caused significant casualties. With major railway accidents happening around the globe, it is fair to say that railway safety all over the world, including in developed countries, needs to be improved further. When analyzing the reasons behind these accidents, most accidents were found to be caused by errors in both controlling train operation and scheduling command. With the rapid development in railways, we are in desperate need of higher-quality safety control technologies for high-speed railway trains.

ix

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Preface

This led Professor Junfeng Wang to write the monograph Safety Theory and Control Technology of High-Speed Train Operation, which was published by Elsevier in 2017. On the other hand, with the continuous expansion of high-speed railway line mileage and network scale, improving the operation efficiency and line capacity of existing high-speed railways has attracted a great deal of attention. The transport capacity of existing high-speed railway lines can be increased further. Many factors affect the transport capacity of high-speed railway lines, such as: • • • • • • •

traditional railway signal concept; lagging technical methods; fixed trains approaching locking route; trains of different speeds running on the same line; unbalanced space-time distribution of passenger transport demand; transport organization mode; and operation schemes.

For completed railway lines, the infrastructure, station structure, line parameters, rolling stock, etc. are all fixed. Railway signaling and transportation organization and dispatching play key roles in giving full play to the effectiveness of these infrastructure and line conditions, and improve the line transportation capacity. Transportation organization and dispatching is a macro traffic control of trains, and railway signaling is a micro individual control of trains. Transportation organization and dispatching achieves dispatching command and control of trains through the railway signaling system, and the two thus complement each other. Theory and Technology for Improving High-Speed Railway Transportation Capacity introduces new methods and technologies to improve the transport capacity of high-speed railway lines from the two aspects of railway signal and transport organization and dispatching in combination with the authors’ completed research projects, published academic papers, and registered patents. In terms of railway signaling, this book breaks through the traditional railway signal concept, shortens the train tracking interval, and improves the line capacity by changing the railway signal rules, increasing the amount of train control information, and optimizing the train control monitoring curve and control algorithm. In the aspect of transportation organization and dispatching, the theoretical system and framework for calculating and improving the capacity of high-speed railways are put forward, and a construction technology of train tracking operation time-space diagram is proposed. A refined station spacing calculation method considering the combination of train operation status, train route, and operation direction is proposed, along with measures to improve the capacity of high-speed railways based on the segmented open mode.

Preface

xi

This book consists of 11 chapters. Chapter 1 summarizes the development history and capacity improvement process of the transportation industry. Chapters 2–7 address methods to improve line capacity in terms of railway signaling. The following aspects are involved: • the development of railway signal technology and its role in improving line transport capacity; • improving train capacity by increasing the information content of the train control system; • improving station capacity based on variable approach locking route rules; • shortening the tracking interval by optimizing the control method of the train control system; • shortening the tracking interval by optimizing the control algorithm; and • the latest international research directions and achievements in improving transport capacity. Chapters 8–11 are concerned with methods to improve line transport capacity in terms of railway transport organization. These chapters address: • the basis for improving the passenger-carrying capacity of high-speed railway stations based on transport organization; • an improved calculation method of station spacing; • an optimization method of blocking sections and train routes in adjacent sections of stations; and • a method summary and numerical experiment verification. Theory and Technology for Improving High-Speed Railway Transportation Capacity is applicable to railway signal control, railway transportation organization and dispatching, and railway transportation equipment. Readers who may particularly benefit from this book include railway transport managers and officials, high-speed railway operation and dispatching commanders, railway signal designers and standard setters, high-speed railway planners, designers, and researchers, next-generation railway signal technology researchers, university teachers and students of railway specialty, etc. This book was written by Professor Junfeng Wang and Professor Baoming Han. Prof. Wang started his first job as a crew member (assistant driver) on a locomotive after graduating with a major in train driving in the early 1980s. During his job, there was a serious collision in the locomotive he had working with a car, resulting in serious injuries to two car drivers and the scrapping of the car. After he experienced that accident, he understood far more profoundly the importance of train operation safety and control. Therefore, he went on to study the profession of

xii

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railway signaling instead of his previous major, and he completed a master’s degree in railway transport automation and communications. After that, he obtained a doctorate in traffic information engineering and control. Over the next 30 years, Prof. Wang was engaged in teaching and research work related to railway signaling. During this period, he hosted or participated in more than 30 research projects, published more than 40 papers in IEEE Transactions on Intelligent Transportation Systems, IEEE Transactions on Reliability, Safety Science, Journal of Advanced Transportation, Journal of Transportation Engineering, and Journal of the China Railway Society, among others. He also patented 12 authorized inventions. Prof. Wang participated in introducing the signaling system technology of China’s first high-speed railway line dedicated to passengers in 2006, Beijing-Tianjin. He participated Chinese high-speed railway CTCS standard-setting. Since 2008, Beijing Jiaotong University has been authorized by the Ministry of Railways to train a large number of technicians in high-speed railway signals on-site. Prof. Wang was one of the main organizers of this program, and was responsible for the teaching of principles and technical specifications in CTCS-2 and CTCS-3. Since then, he has been working in the State Key Laboratory of Rail Traffic Control and Safety, and he served as Deputy Director of the laboratory for 9 years. The contents of this book summarize his long-term on-site railway practice, and his railway signal theory research and teaching results. Prof. Baoming Han is an expert in the field of high-speed railway transportation organization. He has published more than 150 academic papers in journals, including more than 30 Science Citation Index (SCI) and Engineering Index (EI) papers. In the past 30 years, Prof. Han has presided over or participated in more than 100 research projects in the field of highspeed railway transportation organization. His research experience over the years has provided rich theoretical support and research materials for this book. Chapters 1–7 of this book were prepared by Prof. Wang. His students Yalan Chen, Yali Lei, Shule Zhou, Wenjing Yang, and Rong Wang participated in the compilation, material processing, input, and translation of these chapters. During the writing of this book, Prof. Wang has also received encouragement and support from his wife Chen Wei, his daughter Wanrong Wang, his younger brother Jungang Wang, and his colleagues and manager. Chapters 8–11 were prepared by Prof. Han. His students Ruixia Yang, Yiran Yu, Zhe Xi, Xinyu Bao, Shuyi Zhao, Yajie Sun, and Zhixuan Yang participated in the data query and preparation of these chapters. The authors would like to express their heartfelt thanks to all these people, and to those who have also made important contributions to the publication of this book.

Preface

xiii

This book will undoubtedly have shortcomings due to the constraints of knowledge and time, and the authors welcome any comments or improvements from readers. Junfeng Wang Baoming Han

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C H A P T E R

1 Background overview 1.1 Development course of transportation Throughout the development history of transportation industry, from the aspects of the development focus and leading role of transportation industry all over the world, the development of the whole transportation industry can be divided into four stages and three revolutions. Each stage is marked by one or several means of transport, with the goal of improving transport efficiency and transport capacity. Each revolution has brought a profound impact on human society and accelerated the process of social civilization [1]. (1) Water transport stage (from primitive society to the 1920s) In the early stage of human society, land transportation was driven by human and animal power, such as people carrying by hand, carrying on the back, carrying on the head, animals carrying, and so on. With the expansion of the scope of human activities, in order to survive and develop, the earliest means of transportation, rafts and canoes, appeared, and then cars gradually appeared. Then the most primitive routes and roads appeared. The invention and use of ships and cars has brought transportation into a new stage of development, which is the first revolution in the history of transportation. With the use of ships and cars, the postal industry, passenger transport industry and freight industry have developed, and the transportation industry has begun to sprout. The emergence of cars has promoted the development of roads. With the development of land transportation, water transportation has developed particularly rapidly. With the deepening of human understanding of rivers and oceans, the progress of shipbuilding technology, the opening of new routes, the use of compass and the excavation of artificial canals, inland river transportation and coastal marine transportation have developed rapidly. China mastered the wood shipbuilding technology in the

Theory and Technology for Improving High-Speed Railway Transportation Capacity https://doi.org/10.1016/B978-0-323-99700-3.00012-8

1

Copyright © 2023 Elsevier Inc. All rights reserved.

2

1. Background overview

Shang Dynasty, dug the world’s earliest and largest Grand Canal in the Sui Dynasty, and opened the “maritime Silk Road” in the prosperous Tang Dynasty. In the Mediterranean region, the ancient Phoenicians were famous for shipbuilding and navigation. During this period, ships mainly relied on manual fiber pulling and rowing, mainly small sailboats. After the 14th century, long-range, three-masted sailboats powered by wind appeared. With these large sailboats and improved navigation equipment and navigation technology, Europeans left their coast, opened up new routes, sailed around the world, discovered a new continent, entered the era of “geographical discovery” and opened a new chapter in world history. It has a great and profound impact on world politics, economy and culture. The three-masted sailboat has become the symbol of the second revolution in the transportation industry. During this period, compared with the land transportation tools powered by manpower and livestock, water transportation was in an advantageous position in terms of transportation capacity, transportation cost and convenience. Therefore, it is called “water transportation stage.” (2) Railway transportation stage (from the 1830s to 1930s) The two transportation revolutions have made great development in transportation, but the power of transportation tools still depends only on animal power, manpower and wind power. From the 1880s to the early 19th century, steam engines were successively used in ships and trains. The invention of steam engine is an important milestone in human history. Due to the change of power, transportation has developed by leaps and bounds. In 1807, the world’s first steam engine ship “Claremont” was launched in the Hudson River in New York. In 1825, the first railway from Stockton to Darlington was officially opened to traffic, marking the arrival of the third revolution in the history of transportation and the beginning of the railway era. Because the railway could transport passengers and materials at high speed, it almost monopolized the transportation at that time and became the latest and best means of transportation at that time. European and American countries set off a climax of railway construction and expanded to Asia, Africa, and Latin America. During this period, water transportation also developed rapidly. Due to the change of power, ships eliminated the previous phenomenon that navigation depended on trade wind, and could sail in any season. (3) Road, air, and pipeline transportation stage (from the 1930s to 1950s) At the end of the 19th century, with the development of railway transportation, German Benz invented the real car in 1886. With the development of automobile industry, highway transportation rises quietly. Because the highway transportation is flexible, fast and

1.1 Development course of transportation

3

convenient, it not only shows advantages in short-distance transportation, but also shows advantages in long-distance transportation with the emergence of heavy-duty special trucks, various perfect long-distance buses and expressways. World aviation came into being at the end of the 19th century and the beginning of the 20th century. In 1905, the Wright brothers of the United States made a real plane. Due to the speed advantage of air transportation, it plays an important role not only in passenger transportation, but also in freight transportation. With the development of petroleum industry, pipeline transportation began to emerge. In the 1860s, the first wooden pipeline for oil transportation appeared in the United States. Due to the characteristics of low cost, convenient transportation and continuity, pipeline transportation mainly transports chemical fluids such as crude oil, product oil, natural gas, mineral sand and coal slurry. At this stage, railway transportation and water transportation have also made great progress, but the role of highway, aviation and pipeline transportation has been significantly enhanced, which has become the third stage of the development of transportation industry. (4) Comprehensive transportation stage (since the 1950s) Since the 1950s, people began to realize that in the development of transportation industry, water transportation, railway, highway, aviation and pipeline are mutually restrictive and interactive. Many countries began to carry out planned comprehensive transportation and coordinate the relationship between various transportation modes, focusing on the division of labor among railway, highway, aviation and pipeline transportation, Give full play to the advantages of various modes of transportation, show their abilities, carry out intermodal transportation, and build a comprehensive transportation system of sea, land and air three-dimensional transportation. The transportation industry has entered the era of modern transportation. The modern transportation era is characterized by high transportation efficiency, and transportation tends to be high-speed, large-scale and professional. High speed is to improve the running speed of transportation tools, shorten transportation time and increase throughput. It is an important goal of modern transportation. The development of expressway, high-speed railway and supersonic aircraft is the embodiment of this trend. Large scale is to expand the loading capacity of means of transport, which is most obvious in ships. At present, the world’s largest oil tanker has reached 500,000 tons, and cargo trucks are becoming larger and larger. Specialization mainly refers to the specialization of means of transport. Different goods are transported by different means of transport, which is conducive to centralized loading and unloading and technical reform. Container

4

1. Background overview

has the advantages of simplifying packaging, no need for reverse loading during transportation, reducing loading and unloading time, reducing cargo damage and improving delivery speed. It is a better tool for intermodal transportation by road, railway, water and other transportation modes. Container transportation is the most prominent embodiment of specialization. The modern transportation era has realized the modernization of transportation management technology. Transportation departments gradually use information technology for data processing and information transmission, and use various types and scales of electronic computers to form management information systems or networks, which greatly improve the timeliness, accuracy, and economy of transportation information processing and transmission. The decision-making level of the transportation management department has been improved, and the economic and social benefits have been greatly improved.

1.2 Rail transit and transportation capacity In 1825, the first railway from Stockton to Darlington was officially opened to traffic, marking the entry of transportation into the era of rail transit. In 1863, the world’s first underground railway line pulled by steam locomotive was completed and opened to traffic in London, England. Especially by 1879, the successful research of electric locomotive marked the gradual development and maturity of underground rail transit. Rail transit generally has the advantages of large traffic volume, fast speed, dense shifts, safety and comfort, high punctuality rate, all-weather, low freight, energy conservation and environmental protection. Rail transit has become the main choice for people to travel. At present, rail transit is developing toward green, low-carbon and sustainable development. Rail transit is deeply integrated with new technologies such as big data, Internet, artificial intelligence and block chain. Intelligent transportation and intelligent logistics have come to us. In the early 1980s, the number of steam locomotives in China exceeded 8000. The manufacture of steam locomotives was stopped in December 1988 and all steam locomotives were eliminated in December 2005. Diesel locomotives and electric locomotives dominated the whole railway transportation. “Forward Type” steam locomotive has the highest efficiency among all steam locomotives, but it is only 8.42%. That is, 100 shovels of coal were put into the boiler, only about 8 shovels did useful work, and all the other 92 shovels were dissipated from the chimney. Although 8.42% was low, it was in the leading position in the world at that time. The running speed of steam locomotive is 80 km/h and the traveling speed is

5

1.2 Rail transit and transportation capacity

45 km/h. The steam locomotive has slow running speed, low traction force. Limited by the structure of steam locomotive, the maximum line gradient is not allowed to exceed 13 %. Various factors limit the transportation capacity of the line [2]. The comprehensive efficiency of diesel locomotive and electric locomotive exceeds 40%, and the running speed reaches or exceeds 160 km/h. The power of diesel locomotive, especially electric locomotive, is much higher than that of steam locomotive. There is a saying in the industry that “when a steam locomotive goes uphill, it belongs to the dry land to pull spring onions. When a diesel combustion and electric locomotive goes uphill, it accelerates before the slope and then rushes through the slope.” Obviously, diesel locomotive lines and electrified lines are conducive to the substantial improvement of line transportation capacity. In 2008, China opened the high-speed railway from Beijing to Tianjin, with a speed of 350 km/h. Subsequently, Beijing Shanghai high-speed railway, Beijing Guangzhou high-speed railway, Beijing Harbin high-speed railway and Beijing Lanzhou high-speed railway were built. At present, four vertical and four horizontal high-speed railways have been built in China, and eight vertical and eight horizontal high-speed railways are also under construction. By the end of 2021, China has built high-speed railways with a business mileage of more than 39,600 km. As shown in Figs. 1.1 and 1.2.

350km/h

250km/h 350km/h

Qingdao–Taiyuan High-Speed Railway

Beijing–Harbin High-Speed Railway

Beijing-Tianjin Intercity Railway

350km/h

Xuzhou–Lanzhou High-Speed Railway Beijing–Shanghai High-Speed Railway

250km/h

Shanghai–Chengdu High-Speed Railway

Beijing–Guangzho High-Speed Railway

Shanghai-Nanjing Intercity Railway

380km/h 350km/h

Shanghai-Hangzhou Intercity Railway

350km/h

Shanghai–Kunming High-Speed Railway

Hangzhou–Fuzhou High-Speed Railway Beijing–Fuzhou High-Speed Railway

Four North-South Lines Four East-West Lines Other New Lines

FIG. 1.1

Completed four vertical and four horizontal high-speed railway.

350km/h 350km/h 350km/h

6

1. Background overview

FIG. 1.2 Eight vertical and eight horizontal high-speed railway under construction.

The infrastructure quality of high-speed railway has been greatly improved compared with the existing ordinary speed railway. Jointed track is replaced by jointless track, and ballasted track bed is replaced by ballastless track bed. Due to the limitation of railway construction cost, the construction of ordinary speed railway line mostly adopts the form of construction along the river or winding mountains. Obviously, this form is restricted by the curve radius and slope of the line, which limits the transport capacity of the line. The high-speed railway abandons the construction mode of ordinary high-speed railway along the river or winding mountains, and adopts meeting mountain to build road and meeting water to build bridge. The line is straight, the slope is small, and the transportation capacity of the line is naturally improved (Fig. 1.3). At present, the high-speed railway uses new technologies such as Internet, cloud computing, big data and artificial intelligence to improve the intelligent application level and continue to promote the development of high-speed railway to informatization around the four aspects of intelligent driving, intelligent monitoring, intelligent operation and maintenance and intelligent services. High-speed railway signaling system has expanded from the original guarantee of safe and efficient operation of railway to intelligent perception and multisystem cooperative control.

1.2 Rail transit and transportation capacity

7

Joistless track

Jointed track

Ballastless track bed

Ballasted track bed

Meet water bridge Meet mountain road

Along river Winding mountains

FIG 1.3 Comparison of infrastructure between ordinary speed railway and high-speed railway.

The train autonomous operation system based on train-to-train communication shortens the operation interval by means of train-to-train cooperation, further improving the transportation capacity on the premise of ensuring operation safety. Develop high-speed railway moving block technology and automatic train driving technology with a higher degree of automation, further improve transport capacity, reduce energy consumption, further improve the automation level of train operation, reduce the labor intensity of drivers and optimize passenger travel experience. The intelligent driving system can control the train speed more safely, efficiently, comfortably and energy saving, realize the optimal control from single train to train group, and adjust the interval operation strategy according to the operation plan and train operation state to ensure the efficiency of railway transportation. Using advanced sensing, transmission and control methods and technologies, and using the idea of real-time state feedback and intelligent train grouping scheduling, the dispatching command and train operation control are deeply integrated. By improving the data-driven high-speed railway train group cooperative control and dynamic dispatching theory, the integration of intelligent dispatching and train operation optimization

8

1. Background overview

TABLE 1.1 The performance comparison of steam locomotive, diesel locomotive and electric locomotive and high-speed electric multiple unit (EMU).

Steam locomotive


8%

Efficiency Power supply

Diesel locomotive and electric locomotive

>40%

High-speed electric multiple unit >60%

Power concentration

Power distribution

Capacity

2980 h.p.

3860 h.p.

8700 h.p.

7200–14,955 h.p.

Environmental protection

Bad

Poor

Good

Good

Number of drivers

3

2

1

Operating speed

80 km/h

160 km/h

250–350 km/h

Travel time from Beijing to Shanghai

26 h

13–15 h

4.8 h

control is realized, so as to realize the global optimization control of the overall operation efficiency of the road network and comprehensively improve the ability to respond to sudden events in time. The performance comparison of steam locomotive, diesel locomotive, electric locomotive and high-speed electric multiple unit (EMU) is shown in Table 1.1.

1.3 Improvement of line transportation capacity There are many ways to increase railway transport capacity, but there are no more than two forms. One is to add new lines, and the other is to increase the capacity of existing lines. There is no need to say more about building new line. There is a lot of work to do on how to expand the capacity of the existing line and maximize the line transportation capacity. There are many methods for capacity expansion of existing lines, including: (1) Increase the number of station tracks, extend the length of tracks, select large size turnouts, improve the entry or passing speed of train siding, and improve the passing capacity of the station.

1.3 Improvement of line transportation capacity

9

(2) Advanced train control technology and blocking method shall be selected to improve the section carrying capacity. (3) Increase the station marshaling operation and improve the cargo handling capacity. (4) Double track transformation or electrification transformation of existing lines. (5) Operate heavy haul freight trains. (6) Select locomotives with high horsepower and speed. (7) Select new signaling systems, such as centralized dispatching CTC, computer interlocking IL and train overspeed protection system ATP, improve dispatching command level, shorten route handling time and train tracking interval. (8) Select intelligent dispatching command system to improve the dispatching command level. And so on. On December 2, 2009, Lianyungang Yancheng railway was designed to change from single track to double track. The construction standard is upgraded from the original 160 km/h single line to 200 km/h double line. Double track electrification, the main line is 232.2 km long, and it is planned to be completed and opened to traffic in 2012. In 2007, Xining Golmud section was reconstructed into a double track railway, which was completed in 2011. Datong Qinhuangdao railway is 653 km long from Datong City, Shanxi Province to Qinhuangdao City, Hebei Province. It is one of the main channels for the transportation of coal from west to East in China. Daqin Railway is the first new double track electrified heavy haul coal transportation line in China. The whole line was opened to traffic at the end of 1992, and the traffic volume reached 100 million tons in 2002. In order to effectively alleviate the shortage of coal transportation, since 2004, the Ministry of Railways has implemented continuous capacity expansion and technical transformation of Daqin Railway, adopted 2 to 3 high-power locomotives with synchronous operation system for train formation, and operated a large number of 10,000 and 20,000 ton heavy haul combined trains. The traffic volume of the whole line has increased significantly year by year. In 2008, the traffic volume exceeded 340 million tons, becoming the largest railway line in the world last year. On December 26, 2010, Daqin Railway completed the target of annual traffic volume of 400 million tons ahead of schedule, four times the original design capacity. July 15, 2014 HanChang Railway, the double track expansion and reconstruction project (Handan to Changzhi North) runs through the whole line. HanChang railway was built in 1978, with a total length of 221.7 km. In order to alleviate the serious shortage of the original HanChang railway capacity, the expansion and reconstruction project of

10

1. Background overview

HanChang railway was started on September 28, 2010. The main works of the project include: additional double track construction, electrification transformation, upgrading from semiautomatic block to automatic block. The line is a fully enclosed interchange. On December 24, 2019, JinCheng (Jinzhou Chengde) capacity expansion and transformation of railway has been completed. JinCheng railway is an important railway freight channel connecting Northeast China and Guannei, and it is also the main railway transportation channel for coal from Eastern Inner Mongolia to Liaoning. After the implementation of capacity expansion and transformation, the railway grade has changed from class II to class I, single line to double line, electric traction has been realized for the whole line, and the allowable speed of the line has been increased from 100 to 120 km/h. In 2021 alone, there will be 10 single-line substation, double line, and electrification transformation projects in China [3]. It includes JiaHe Railway (Jiamusi Hegang) reconstruction project, and after the reconstruction, the total length of the line is 71.6 km, and the design speed is divided into 160 and 200 km/h. At that time, the traffic time from Hegang to Jiamusi will be reduced to less than 40 min. At present, it has officially entered the track laying construction stage and is expected to be opened to traffic next year. Chengdu railway hub ring line upgrading project, at present, the survey and design of the project has completed the bidding. The reconstruction project includes the construction of Chongzhou EMU Operation Place and related projects, the reconstruction of hub loop line and related tie line projects. In double track reconstruction project of Guizhou Guangxi Railway (Longli station Liuzhou station), after the completion of the double track, Guizhou Guangxi railway will change from single track to double track operation, greatly improve the passenger and freight transportation capacity of Guizhou Guangxi railway, effectively alleviate the shortage of freight channel capacity of Guizhou south to Guangxi railway, and the transportation time of channel trains in the western land and sea channel will be shortened from 53 to 23 h. In quality improvement project of Xining Golmud section of Qinghai Tibet railway, at present, the feasibility study report of the project has been approved, and the construction period is 1.5 years. After the transformation, the whole Xining Golmud section operates 160 km/h power centralized EMU trains, and the operation time can be controlled within 5.2 h, with a minimum time of 4.8 h. Related reconstruction projects of Hunan Guangxi Railway include capacity expansion and reconstruction of Liuzhou hub, additional second-line project from Zhegujiang station to Qingmao station (included), and new double-line project from Qingmao station (excluded) to Liuzhou West Station. The design driving speed is 80 to 160 km/h.

1.4 Railway signaling transportation organization and line capacity

11

In Chengdu Kunming railway capacity expansion and reconstruction project, Mianning Miyi section is planned to be put into operation by the end of this year, and Emei Mianning section is planned to be put into operation in 2023. In addition, Mianning station reconstruction project is nearing completion and will be opened on August 30. Capacity expansion and reconstruction of Chengdu Longchang section of Chengdu Chongqing Railway: in early July, the project survey and design bidding announcement was issued, including the whole process of prefeasibility study, feasibility study, preliminary design and construction drawing design (including construction cooperation). The planning and construction of the project is led by China Railway Chengdu Bureau, and the next step is to strive to incorporate the project into the national railway development plan of the 14th five year plan. Nanjing Wuhu railway double track project: the preliminary review and planning site selection of Anhui section were passed in early July, which laid a foundation for accelerating the construction of the project. Capacity expansion and reconstruction of LongXu section of LongHuang Railway: the first section was started in June this year. At present, land acquisition and demolition and control project construction have been fully started. The construction of Simakan middle bridge in Luxian County, Hushi bridge in Longmatan district and Tuojiang super large bridge in Jiangyang district have been started, and the construction of large facilities such as beam making yard and reinforcement processing yard has been ready to enter the site. Electrification transformation of broad Railways: at present, Yunnan Guangtong Dali the reinforcement of railway equipment and electrification transformation have been successfully completed. After the transformation, the train traction mode will be changed from diesel locomotive to electric locomotive, and the original arrival departure track of some stations will be extended from 450 meters to more than 880 meters. The marshaling capacity of freight trains will be expanded, and the overall transport capacity will be greatly improved, which will greatly alleviate the tension of transport capacity from Kunming to Western Yunnan.

1.4 Railway signaling transportation organization and line capacity For the completed railway line, the infrastructure, station structure, line parameters, rolling stock, etc. shall be fixed. How to give full play to the efficiency of these infrastructure and line conditions and improve the line transportation capacity, transportation organization and dispatching and railway signaling play a key role. Transportation organization and dispatching is the macro and large-area control of trains, and railway signaling is the micro and local control of trains. Transportation organization

12

1. Background overview

and dispatching realizes the dispatching, command and control of trains through railway signaling system, and the two complement each other. At present, transportation organization and dispatching and railway signaling are developing in the direction of integration, deep integration and real-time comprehensive response. On June 30, 2011, the Beijing Shanghai high-speed railway was put into operation, with a total length of 1318 km and 24 stations. The transportation organization mode of Beijing Shanghai high-speed railway finally chose the transportation organization mode of mixed running of highspeed and medium-speed. That is, the design speeds of high-speed and medium-speed trains are 350 and 250 km/h, respectively. Vertical rectangular comprehensive maintenance skylights are adopted for the whole line of Beijing Shanghai high-speed railway, and the skylight time is 360 min. The mixed running mode greatly reduces the transport capacity of the line. From the perspective of transportation organization, when high-speed and medium-speed trains run on the same line and there is overtaking in the train workshop in the section, the difference between the running time of high-speed and medium-speed trains in the same section will become a key factor in the section carrying capacity of nonflat graph. The greater the time difference, the greater the impact on the carrying capacity. When the speed difference of different kinds of trains is large, the distance between stations and the inequality of sections have a great impact on the carrying capacity. Generally speaking, the longer the distance between stations, the greater the difference between the operation time of high-speed and medium-speed trains and the smaller the carrying capacity. From the perspective of signaling, why does the mixed running mode of high speed and medium speed reduce the line-carrying capacity? One block section of China’s 350 km/h high-speed train consists of two track circuits, with a length of about 2000 to 2400 m. One block section of 250 km/h medium-speed train is composed of a section of track circuit, with a length of about 1000 to 1200 m. According to the train tracking mode of automatic signal block, the target point of the following train is the beginning of the block section occupied by the preceding train. When the preceding train is about to leave the current block section, it wastes the efficiency of a block section for following train. When the 250 km/h train enters the high-speed line, it wastes a block section, and the length of the block section increases from 1000–1200 to 2000–2400 m. Obviously, the carrying capacity is greatly reduced. Chapter 5 of this book puts forward “An Adaptive Dynamic Coding Method for Track Circuit in a High-Speed Railway,” which can not only further improve the 350 km/h line capacity, but also solve effectively the problem of reducing the capacity of high-speed and medium-speed mixed running lines [4].

1.4 Railway signaling transportation organization and line capacity

13

This book breaks through some traditional railway signaling concepts and combines modern new technologies to put forward “improving train transport capacity by increasing the amount of train control system information,” “improving station transport capacity based on variable approach locking section rules,” and “reducing tracking interval by optimizing train control system control methods” to “shorten the tracking interval through control algorithm” and a series of methods to improve the line capacity through railway signaling. In addition, this book systematically expounds the basic methods of improving the transport capacity of the existing signaling system, as well as the latest international research direction and research results of improving the transport capacity.

1.4.1 Railway signaling and line capacity The function of railway signaling is to command train operation, ensure train operation safety and improve transportation efficiency. Improving efficiency is to maximize the operation efficiency of existing equipment and trains and improve the line transport capacity. Railway signaling is divided into station signal control system, section signal control system, train operation control system, marshaling station shunting control system, etc. Generally it includes station interlocking, block, cab signal, overspeed protection, dispatching centralization, shunting yard control and road crossing signal. Railway signaling is the general name of signal equipment, system and signal technology. In 1825, railway signal was born with the emergence of the first train in Britain. Railway signal has been closely related to transportation efficiency since its birth. In order to shorten the train tracking interval and improve the section passing capacity, Cook, an Englishman, invented the section blocking technology in 1842. The development of block technology has experienced interstation block, automatic block, virtual block, mobile block, etc. Interstation block includes telephone block, sign block, signboard block, semiautomatic block, and automatic interstation block [5]. The continuous development of blocking technology gradually shortens the train tracking interval, improves the equipment efficiency and improves the line capacity. At present, China mostly adopts semiautomatic block or automatic inter station block in single track railway, and three display automatic block or four display automatic block in existing double track railway. Automatic block equivalent to eight display is adopted for high-speed railway, virtual block is adopted for Qinghai Tibet line, and moving block is tested in a section for Shuohuang heavy haul railway and Qinghai Tibet line [6].

14

1. Background overview

The first set of mechanical station interlocking control equipment was born in 1856. Station interlocking has experienced the development stages of full mechanical interlocking, electromechanical interlocking, relay interlocking, computer interlocking, and so on. Interlocking technology realizes the interlocking of station route, turnout and signal, completes the establishment, locking and unlocking of train or shunting route, and avoids front and side conflicts of trains. At the same time, the route handling time and unlocking time are reduced, the equipment utilization rate is improved, and the passing capacity of the station is improved. At present, China mostly adopts 6502 relay interlocking in ordinary speed railways and computer interlocking in high-speed railways [7,8]. In 1925, American S.N. White put forward the operation mode of driving according to signal display in railway section, which was adopted by American Railway Society (AAR) and named Centralized Traffic Control (CTC). It is characterized by the combination of signal and monitoring train operation, and commanding train operation in the control center. The first set of centralized dispatching equipment was installed and used on the Stanley Berwick railway of New York Central Railway on July 25, 1927. In the 1930s, France, the Soviet Union, Sweden, and Switzerland successively used centralized dispatching. In 1962, the relay polarity frequency centralized dispatching system was first installed in Baofeng section of BaoJi Chengdu Railway. In 1969, DD-1 scheduling centralization of transistor discrete components was applied, and then DD-2, DD3-f, dd-3, D4D, D4, and D5 scheduling centralization of integrated circuits appeared. These centralized dispatching systems failed to achieve the desired effect and were stopped in the late 1970s. In 1996, China began to implement the construction of railway transportation dispatching command and management information system (DMIS). DIMS is combined with railway transportation management information system (TMIS). In 2005, the merged system was renamed railway Train Operation Dispatching Command System (TDCS) for centralized control of normal speed railway dispatching. On November 28, 2003, the new generation CTC was opened and put into trial operation in Xining Hargai. The new generation CTC takes the train operation dispatching command system as the platform and uses modern computer technology, network technology and wireless communication technology to realize the planned operation of train and shunting operation. The station self-discipline machine automatically arranges the train route according to the train operation plan, and automatically executes the shunting operation plan according to the actual situation of train operation and the principle of train priority. The application of key technologies such as wireless transmission system of dispatching command, wireless train dispatching large triangle (dispatcher, station attendant and driver) communication, wireless train number automatic tracking

1.4 Railway signaling transportation organization and line capacity

15

and verification system, wireless shunting locomotive signal and monitoring system has significantly improved the intelligence and automation level of the new generation CTC in automatic adjustment of train operation plan and automatic execution of shunting plan. Transportation efficiency and line capacity have been greatly improved. At present, China’s high-speed railways have all adopted the new generation CTC system. At first, the train operation control is that the driver completes the traction, coasting, and braking of the train according to the signal display, so as to realize the start, cruise and parking functions of the train, as well as the train overspeed protection and prevention signal. With the development of new technologies such as computer, communication and control, train operation control equipment is installed on the train. The driver’s driving operation is gradually replaced by equipment until automatic driving and intelligent driving are realized. In 1964, the train control system of Shinkansen ATC system in Japan was put into operation. In the early 1980s, the German LZB system began to be applied. In 1981, the French TVM300 equipment was put into operation in Paris-Lyon, and its speed monitoring mode is lag stepped. In 1993, TVM430 equipment was put into operation in the North high-speed line, and its speed monitoring mode is segmented curve type. In 2001, the European Commission established ETCS (European train control system) as a mandatory technical specification through legislation. The application of train control system changes the train operation control from an open-loop control to a closed-loop control. The train control equipment plays a leading role, avoiding the driver’s blindness, randomness and uncertainty in driving. Before 1980, China had no on-board equipment for train operation control, and there was even no train speedometer on steam locomotives. The driver judges the train speed by feeling, counting the number of poles and observing the clarity of ballast. After 1980, it began to install three major signal parts of locomotive, namely automatic parking device, cab signal and wireless train dispatching. After installing the three signal major parts of the locomotive, the traffic accidents decreased by 84%, which greatly improved the safety and efficiency of train operation. From 1990 to 2007, the three major signal parts of locomotive were upgraded. The automatic parking device is upgraded to the train monitoring and recording device LKJ2000, the cab signal is upgraded to the main signal, and the driver can drive by the cab signal. The Automatic Train Protection (ATP) equipment, was used in high-speed train control systems CTCS-2 and CTCS-3 in 2008, and automatic driving equipment was added a few years later [9]. The working principle of train control system is that the ground equipment of train control system generates movement authorization information according to the current position of the train and combined with

16

1. Background overview

operating conditions, and sends movement authorization to the train. Provide train control data such as temporary speed limit, route information and line description information. The on-board equipment generates dynamic speed curve according to mobile authorization, line description information, temporary speed limit and other information to monitor the safe operation of the train. If the actual running speed of the train exceeds the allowable speed, the on-board equipment will implement service braking or emergency braking to prevent the train from speeding and entering the signal. The train speed control mode is divided into speed code step control mode and speed distance curve control mode. The speed code ladder control mode controls only one speed level in a block section. In a block section, only one speed is used to judge whether the train is overspeed. It includes: outlet inspection mode (lag control) and inlet inspection mode (advance control), as shown in Fig. 1.4. The speed distance curve control mode is a curve reflecting the relationship between the allowable train speed and the target distance determined according to the target speed, line parameters, train parameters, braking performance, etc. The speed distance curve reflects the allowable speed value of the train at each point. The train control system gives the current allowable speed of the train in real time according to the speed distance curve. When the train exceeds the current allowable speed, the equipment will automatically implement service braking or emergency braking to ensure that the train can stop before the parking place. It includes segmented speed distance curve control mode and primary speed distance curve control mode.

FIG. 1.4 Speed code step control mode.

1.4 Railway signaling transportation organization and line capacity

FIG. 1.5

Schematic diagram of step speed control and sectional speed curve control.

FIG. 1.6

Schematic diagram of primary speed distance curve control mode.

17

Different train speed control modes have a great impact on train operation efficiency. As shown in Figs. 1.5 and 1.6, for the same parking point, three block sections are required for step and sectional speed control to complete the braking process, and only two block sections are required for primary speed curve control mode to complete the braking process. Obviously, the primary speed curve control mode improves the train operation efficiency and the line capacity.

1.4.2 Transportation organization and dispatching and line capacity High-speed railway needs to meet the demand of large passenger volume. It is necessary to reasonably determine the passenger train operation section, train type, operation pairs, and train arrival and departure times. At the same time, in case of emergencies, it must also be able to respond in time to minimize the delay time of the train. These two aspects constitute the main content of high-speed railway dispatching. Therefore, highspeed railway dispatching is the key to ensure the efficient operation of high-speed railway and improve transportation capacity. According to the organization mode, train dispatching can be divided into two aspects: operation scheme and operation plan. The operation scheme is based on the passenger volume to scientifically and reasonably determine the train operation section, the running pairs

18

1. Background overview

and the train operation route according to the character, characteristic and rule of passenger flow. The operation plan mainly establishes the sequence of each train occupying the section, the arrival and departure time of the train at each station, the passing time and the operation time of the train in the section on the basis of the operation scheme. These two aspects constitute the static dispatching of high-speed railway trains. When an emergency occurs, which makes the train unable to operate according to the scheduled plan, the basic train operation diagram needs to be adjusted. Train diagram adjustment can make the train reach the destination as soon as possible by adjusting the train operation route. Secondly, adjust the departure and arrival time of the train at the operation planning level or reduce the operation time of the train section to minimize the train delay time. These two aspects constitute the dynamic dispatching of high-speed railway trains. Therefore, the train scheduling of the whole high-speed railway includes dynamic scheduling and static scheduling of operation scheme, as well as dynamic scheduling and static scheduling of operation plan. The train can reach the destination as soon as possible by adjusting the train route; secondly, the train departure and arrival time can be adjusted or the train operation can be reduced to minimize the train delay time at the operation planning level. These two aspects constitute the dynamic dispatching of high-speed train. Therefore, the whole high-speed railway train dispatching includes dynamic dispatching and static dispatching of the train operation district program, as well as dynamic dispatching and static dispatching of the operation plan. The following lists some technologies, methods and research results of transportation organization and dispatching to improve line capacity. Reduce the loss of mixed running capacity and improve the line capacity. Beijing Shanghai high-speed railway has selected the transportation organization mode of mixed running of high-speed and mediumspeed. That is, 350 and 250 km/h trains run together. High-speed and medium-speed mixed running mode is suitable in the early stage of Beijing-Shanghai high-speed railway operation and small passenger flow. However, with the continuous and rapid growth of passenger flow, the shortcomings of consumption capacity of mixed running mode become more prominent. According to Jin-Zi et al. [10], it is calculated that the carrying capacity is 149 pairs of trains under full high-speed mode and 82 pairs of trains under mixed running mode. Optimize the operation scheme and operation plan through transportation organization and train dispatching. Reasonably arranging the tracking sequence of fast and slow trains and making use of the reasonable passing of stations can effectively improve the train operation density and reduce the degree of mixed running loss elimination ability.

1.4 Railway signaling transportation organization and line capacity

19

The high-speed train slows down in advance when entering the station to improve the line capacity. Station arrival tracking time interval is the key to affect the capacity of the whole line compared with section tracking time interval and station departure time interval. If the requirements of and section tracking interval are met, the train needs to slow down in advance when entering the station. The deceleration value is related to the length of station throat section, braking deceleration and turnout size [11]. It improves the overall transport capacity of the high-speed rail network through the coordination of transport capacity of the high-speed rail network, carries out research on the connotation, objectives, constituent elements, and influencing factors of high-speed rail network transport capacity coordination, and reveals the law of transport capacity coordination among high-speed rail network systems. It includes the following: (1) conduct a comprehensive and systematic analysis of the high-speed rail network from the perspective of transport capacity supply system, and analyze the constituent elements, functions, operation processes, interaction processes of each system of high-speed rail network transport capacity. (2) Analyze the connotation of transport capacity coordination of high-speed railway network. Through the analysis of the characteristics and contents of the coordination of high-speed railway station capacity, high-speed railway line section capacity and motor train station capacity from the aspects of total capacity, capacity utilization and capacity elasticity, the scope of high-speed railway network capacity coordination is defined. Study the impact of service level, network scale and network structure on the transport capacity coordination of high-speed railway network system. The laws of static coordination and dynamic coordination of high-speed rail network transportation capacity system are studied. (3) Build a static and dynamic coordination index system that can fully reflect the coordination of high-speed rail network from the aspects of total capacity, capacity utilization and capacity elasticity, and study the evaluation method [12]. In order to maximize the carrying capacity of high-speed railway with multilevel trains and ensure the transportation quality, a train diagram optimization model under the condition of maximizing the carrying capacity of high-speed railway network is constructed. According to the characteristics of no conflict during train operation, the problem is abstracted as the constrained maximum independent set problem in spatiotemporal network. The model is transformed and linearly relaxed by D-W decomposition. The column generation algorithm is used to solve the relaxation problem with large-scale decision variables. Based on the relaxation solution, a branch and bound algorithm is designed to obtain the maximum independent running line set of the optimal feasible train. The results show that the model has the function of flexibly obtaining an

20

1. Background overview

effective train diagram considering both transport capacity and transport quality under the demand scenarios represented by different parameters. Compared with the commonly used heuristic algorithms for solving independent set problems, this method can increase the throughput value by 2.56% and the total target value by 4.6% while maintaining the average fluctuation of travel time of 1.33% [13]. For the optimization of high-speed train operation scheme for OD passenger flow, a multiobjective optimization model of train operation scheme based on dynamic passenger flow is established. The optimized operation scheme not only maximizes the travel needs of passengers, improves economic benefits and reduces the travel costs of passengers. The total number of train stops after optimization is lower than the original, and the stop scheme is more balanced [14]. Under various constraints such as section carrying capacity, station departure capacity and train carrying capacity, taking the weighted sum of train operation time and passenger travel time as the optimization objective, a Stackelberg game model for the optimization of high-speed train operation scheme facing time-varying demand is constructed [15]. After optimization, the coincidence between the high-speed train operation scheme and the timevarying demand of passengers is improved, and the deviation between passengers’ boarding time and planned departure time is reduced.

References [1] https://zhidao.baidu.com/question/1179019552316446899.html. [2] https://zhidao.baidu.com/question/1821836391764452068.html. https://baike.baidu. com/item/%E8%92%B8%E6%B1%BD%E6%9C%BA%E8%BD%A6/2309698? fr¼aladdin. [3] https://new.qq.com/rain/a/20210820a0fw8t00. [4] J. Wang, H. Zhang, R. Kang, P. Xu, An adaptive dynamic coding method for track circuit in a high-speed railway, IEEE Intell. Transp. Syst. Mag. 02 (2021) 2–13. [5] X. Kai, M. Zhang, L. Wang, Development and research of railway block technology, Railw. Signal. Commun. 55 (S1) (2019) 60–67. [6] L. Qi, Great breakthrough in heavy-haul mobile block technology of Shuohuang Railway, World Rail Transit 7, 2021, 44-45. [7] C. Jia, H. Zhang, Z. Qi, Development trend of interlocking and train control system of China railway, Chin. Railw. 02 (2020) 1–5. [8] W. Duan, Overview of railway stations of interlocking development in China, Railw. Signal. Commun. 55 (S1) (2019) 86–97. [9] R. Zhang, The present situation of railway signal at home and abroad, the contrast of difference and the thinking of the development direction of railway signal in China, Railw. Standard Des. 07 (2004) 117–120. [10] J. Zheng, J. Liu, Carrying capacity of Beijing-Shanghai high-speed railway by different transport organization patterns, J. Transp. Syst. Eng. Inf. Technol. 12 (4) (2012) 22–28. [11] X. Shi, Research on train tracking interval time of passenger dedicated line in China, Chin. Railw. 05 (2005) 32–34.

References

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[12] T. Chen, F. Tian, R. Ren, et al., Review of the research on high-speed railway network capacity, J. Transp. Eng. Inform. 19 (3) (2021) 5l–58. [13] C. Lu, L. Zhou, R. Chen, Optimization of high-speed railway timetabling based on maximum utilization of railway capacity, J. Railw. Sci. Eng. 15 (11) (2018) 2746–2754. [14] H. Tian, D. Wang, M. Shuai, K. Li, Optimization of high-speed train operation plan for OD passenger flow, J. Northeastern Univ. 41 (11) (2020) 1535–1542. [15] H. Su, F. Shi, L. Deng, et al., Time-dependent demand oriented line planning optimization for the high-speed railway, J. Transp. Syst. Eng. Inf. Technol. 16 (5) (2016) 110–116.

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C H A P T E R

2 High-speed railway signal technology and transport capacity 2.1 Train operation control system 2.1.1 Introduction of train operation control system Train Operation Control System is the key technical equipment to ensure the safe operation of trains and improve the transport efficiency, which is composed of ground equipment and on-board equipment. Fig. 2.1 is the Chinese CTCS-3 + ATO train control system structure diagram. The ground subsystem is composed of Radio Block Center (RBC), Temporary Speed Restriction Server (TSRS), balise, and other components. According to the status of the controlled train, the information of track occupation, train route status, temporary speed limit order, disaster protection and route parameters, the train Movement Authority (MA) information is generated by RBC. And RBC transmits to the on-board subsystem through GSM-R wireless communication system to ensure the operation safety of the trains within its jurisdiction. RBC temporary speed limit command distribution and centralized management is realized by TSRS according to the dispatcher’s temporary speed limit command. The balise provides reliable ground fixed and variable information to train control on-board equipment. The vehicle equipment mainly includes Vital Computer (VC), Radio Transmission Module (RTM), Balise Transmission Module (BTM), Track Circuit Reader (TCR), Speed and Distance measurement Unit (SDU), driver-computer interface (DMI), Judicial Recording Unit (JRU) and Train Interface Unit (TIU). The VC is the core processing unit of the on-board

Theory and Technology for Improving High-Speed Railway Transportation Capacity https://doi.org/10.1016/B978-0-323-99700-3.00001-3

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Copyright © 2023 Elsevier Inc. All rights reserved.

FIG. 2.1 CTCS-3+ ATO train control system structure diagram.

2.1 Train operation control system

25

equipment. It integrates the train data, line description, MA and temporary speed limit information to generate the dynamic speed monitoring profile, and automatically monitors the train operation according to the speed monitoring profile. Output a braking order to the train when necessary to ensure the safety of the train. The RTM connects with GSM-R vehicle radio to realize vehicle-to-ground two-way information transmission. The information of train’s speed, position and state is transmitted to RBC by RTM. The RBC transmits control information such as MA to on-board equipment. The BTM receives the balise information disposed on the line through a balise antenna installed under the train. The TCR receives the track circuit information through the TCR antenna. Based on the data of speed sensor and radar, the speed, distance and direction of the train can be calculated by the SDU. The VC transmits the information of train’s position, speed, grade and mode to the DMI in real time. In addition, when the driver manipulates the DMI device, the DMI transmits the information to the VC in time to adjust the status of the train. In summary, ground equipment is responsible for issuing MA and control information to the trains under its jurisdiction based on train occupancy and route status. The on-board equipment is responsible for the comprehensive processing of the train operation control information, generating the target distance pattern profile, and controlling the train safe operation.

2.1.2 Improvement of transport capacity with the development of block system(techniques) The space interval method, which was introduced by the British in 1842, was widely adopted because it could ensure the train safety, and gradually formed the block system of railway. With the development of block technology, the number of trains operation between stations is increasing, and the transport capacity of railway lines is increasing. Block technology shortens the train tracking time and is one of the main methods to improve the railway transport capacity. Block technology has experienced interstation block, automatic block, virtual block, moving block and so on. 2.1.2.1 Interstation block (1) Artificial block The departure of the train is based on the train staff or the guidepost. The station attendant and the driver need to pick up the train staff or the guidepost. Only one train is allowed between the two stations. There is no interlocking relationship between the two stations.

26

2. High-speed railway signal technology and transport capacity

(2) Semiautomatic block By manually going through the train liaison procedures, taking the open display of the departure signal machine as the travel voucher, the train leaves the station and is pressed onto a dedicated track circuit, and the departure signal machine is automatically shut down before the train reaches the other station, two stations of the outbound signal cannot be opened again by blocking methods. (3) Automatic interstation block Under the condition of using axle-counting equipment or track circuit to check the block occupation, the method of automatic block is adopted. 2.1.2.2 Automatic block Interstation lines are automatically blocked into a number of blocks, and set signal at the entrance of each block (including set the home and starting signal in the station). When the train enters the block, the partition automatically turns to the block state, and when the train leaves, it automatically turns to the open state without going through the block procedure. Taking the CTCS-3 train control system as an example, and the train operation is shown in Fig. 2.2. The train can run in the interval according to the block section which is fixed. It is mainly used in the double-track section. For single-track section, with the development of satellite positioning, mobile communication and other technologies, a new train control system based on virtual block can be used to track trains in single-track section. At present, the ITCS train control system and virtual block mode are used in Qinghai-Tibet railway. Double track automatic block includes the following four ways: (1) Automatic block of AC counting code track circuit The automatic block of the AC counting code track circuit is realized on the basis of the AC counting track circuit. The track circuit is used as a channel to transmit the counting code information, and the signal display is automatically controlled by the code to control train tracking.

Preceding Train F

F

Track Circult

F

TC0 TC1 TC2 TC3 TC4

F

TC5 TC6

TC7

F

TC8

F

F

F

TC9 TC10 TC11 TC12 TC13 TC14 TC15 TC16 TC17

TCS Information

L5

L4

L3

L2

L

LU

U

HU

Blocking

B0

B1

B2

B3

B4

B5

B6

B7

FIG. 2.2 CTCS-3 automatic block interval operation diagram.

B8

2.1 Train operation control system

27

(2) Automatic blocking of polar frequency pulse The automatic blocking of polar frequency pulse is to send the DC pulse signal with certain polarity and certain frequency to track and control the display of wayside signal. (3) Automatic block with audio frequency shift modulated track circuit Frequency shift is a kind of frequency adjustment mode, it is the carrier frequency signal F0, with low frequency modulation signal FC control, making F0+ Δf and F0 ΔF alternating change. This modulation mode is called frequency shift, short for FS. The carrier frequency of F0 is 550, 650, 750 and 850 Hz, the frequency deviation of Δf is  55 Hz, and the modulation frequency of F0 is 11, 15, 20 and 26 (Hz) low frequency signals, which can meet the needs of three display automatic blocking. The application of 18 information frequency shift automatic block successfully solved the problems of less information, low signal to interference ratio and long strain time of the original frequency shift equipment. (4) ZPW-2000 jointless track circuit with four display automatic block ZPW-2000 carrier frequency F0 uses 1700, 2000, 2300 and 2600 Hz. Frequency deviation Δf is  11 Hz, and modulation frequency Fc uses 10.3 29 Hz 18 low frequency signals according to 1.1 Hz increasing, which can meet the need of seven display automatic blocking. Single track automatic block includes the following two ways: The transportation capacity of single-track cannot meet the transportation demand, the investment of double-track is large and the construction period is long, and the transportation capacity is limited by increasing station density. Through the improvement of block system, the transport capacity of the line can be effectively improved. (1) Automatic block with axle counter The occupancy check of the block section is accomplished by the axlecounting equipment set at both ends of the block section, and then the method of tracking the train is used to expand the capacity. For example, the passing capacity of the original semiautomatic block in the GUANGMA section of Baocheng line is 20 pairs of trains, and the passing capacity of the train is improved from 2.5 to 3 pairs after the automatic block with axle counter is opened. (2) Virtual automatic block Train occupancy inspection in Virtual Block is realized by train active positioning and vehicle-to-ground wireless communication technology, that is, Radio Block Center (RBC) which set on the ground, and on-board equipment with comprehensive positioning function. Because

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2. High-speed railway signal technology and transport capacity

there is no track circuit and signal in the block and station, the maintenance workload of rail-side equipment is greatly reduced. For example, Europe’s hybrid ERTMS/ETCS-3 system uses fixed virtual blocks to separate trains equipped with train integrity monitoring systems (TIMS), reducing the cost of rail-side implementation and improving performance. As the virtual automatic block is relatively fixed block, the length of block is further shortened, and the line capacity is improved.

2.1.2.3 Moving block Trains are no longer subject to block, and the tracking train can approach the rear of the train at the shortest safe distance based on the current train speed. (1) “Static” tracking moving block The movement authority calculation of the rear train only uses the position condition of the front train, and the end point of the movement authorization is the front train back end, also known as the “Hard wall” moving block. The train relies on wheel speed sensors, radar and balises for safe positioning and reports its position to the Zone Controller (ZC). ZC tracks and manages the trains in the control area according to the position of the train report. It calculates the movement authority for the trains according to the station’s route state and the position of each train, and sends it to the train control on-board equipment through the train-to-ground wireless communication network. The on-board equipment generates the primary mode control profile according to the movement authority sent from the ground and the line data stored by itself, and monitors the train operation [1]. (2) “Dynamic” tracking of moving block With the development of wireless communication technology, the capacity and time delay of vehicle-vehicle and vehicle-ground-workshop increase greatly, which improves the condition of “Dynamic” train tracking and further reduces the tracking interval between two trains. As shown in Fig. 2.3, the calculation of Train 2’s movement authority will be based on “Static” mobility tracking, minus train 1’s emergency braking distance L1-brake. The calculation of rear train’s movement authority will not only use the position of the front train, using the speed and braking distance of the train in front, the movement authority endpoint extends an emergency braking distance of the train in front on the basis of the rear end of the train in front. This train tracking mode is called “Dynamic” tracking moving block, also known as “Soft wall” moving block.

29

2.1 Train operation control system

Train Operation Direction 2

1

L

L1−brake

2

1

L2−brake FIG. 2.3

Lsafe

Ltrain

“Dynamic” tracing moving block schematic.

2.1.2.4 Efficiency comparison of interstation block and automatic block When a single-track section uses interstation block, only one train can run in the block, and its capacity is related to the density of the station. When the transport capacity of single-track section is tight, and the condition of repair line is not available, the usual method is to increase the capacity of the line by increasing the number of stations. The technology of automatic block and moving block in single-track line is an effective measure to improve the transportation capacity from signal equipment. The use of automatic block in single-track can improve the operation efficiency by more than 70%. It should be noted that in addition to different block modes, the improvement of operation efficiency depends on many factors, such as station setting, number of railway tracks and operation plan. 2.1.2.5 Efficiency comparison of automatic block and moving block (1) Comparing the efficiency of automatic block with that of “Static” tracking moving block The capacity of automatic block line is related to the length of block and the speed of tracking train. When the train speed is less than 120 km/h, the efficiency of “Static” tracking moving block is better than that of automatic block. With the increase of train speed, the advantage of “Static” tracking moving block is not obvious compared with automatic block. The main reason is that the braking distance of train increases with the higher train speed, and role of the block length decreases. (2) Comparing the efficiency of “Static” tracking moving block with that of “Dynamic” tracking moving block

30

2. High-speed railway signal technology and transport capacity

The “Dynamic” tracking interval reduces an emergency braking distance of the train in front compared to the “Static” tracking. The emergency braking distance increases with the higher train speed. Assuming that the two trains running before and after using the same speed grade, “Static” tracking of the moving block train interval (time) increases and “Dynamic” tracking does not increase with the increase of train speed. 2.1.2.6 Practical application At 2021, the Shuohuang Railway became the first heavy haul railway in China to adopt a moving blocking system. This is a major breakthrough in China’s heavy haul railway technology. Moving block is an optimal train control mode for improving safety index and transport efficiency in international railways [2]. For the first time, Shuohuang Railway has established the heavy-haul moving blocking technology system which meets the actual operation demand of heavy-haul railway in China, and conquered the technology of moving blocking security protection and control for the complex scene of heavy-haul railway The repositioning technology of heavy-haul train based on TD-LTE wireless communication and Beidou satellite navigation is applied for the first time, and the RAMS integrated support technology for China heavy-haul moving block train control system is realized. With the application of moving block system technology, the average train departure interval has been shortened from 11 to 7.3 min, and that has been shortened by 34%. It is estimated that the annual traffic volume of the whole Shuohuang railway line can be increased by 40 million tons after the renovation of the moving block, and the cost of comprehensive maintenance of the signal system equipment can be reduced by about 20%. At the same time, the tracking ability can be improved, and the locomotive turnover time can be reduced, the locomotive turnover rate is increased by 10%. Real-time safety protection can also be carried out to reduce the intensity of the driver’s work and reduce the driver’s accidents by 51%. It also plays an active role in reducing the work intensity of the driving and maintenance staff.

2.1.3 Enhancement of transport capacity with device-priority control or driver-priority control Train control system is classified according to man-machine relationship, which is mainly divided into two categories. The driver brake priority (man-control priority) is generally adopted for on-board equipment in the incomplete monitoring mode, and the equipment brake priority (machine-control priority) is generally adopted in the complete monitoring mode. In the target speed monitoring area with full monitoring mode,

2.1 Train operation control system

31

when the target speed is 0 and the allowable speed is less than 40 km/h, the driver braking priority is adopted. DMI shows “Driver control” when people control takes precedence. DMI shows “Machine Control” when machine control takes precedence [3].

2.1.3.1 Driver priority control The driver control priority of TVM300/430 system in France, only when the speed of the train exceeds the speed allowed for safe operation, the equipment will carry out punitive forced braking, and the equipment will not interfere with the driver operation when the train is operation normally [4]. In driver-controlled priority mode, the driver can exert his initiative, and when the current speed exceeds the maximum allowable speed, the driver can reduce the speed manually. No matter what kind of braking priority is used, if emergency braking occurs, only meeting the parking condition can be alleviated.

2.1.3.2 Equipment priority control In the form of equipment priority control, represented by Shinkansen, braking control is carried out immediately when the train speed exceeds the target speed, and automatic relief is achieved when the train speed falls below the target speed without the driver’s participation. The advantages are that the safety is good, the burden on the driver can be minimized, and the track interval of the train can be shortened [4]. The equipment control priority can alleviate the brake in time, preventing the train continues to decelerate. The two modes affect the train tracking interval, and it is obvious that the priority of equipment control is beneficial to improve the transport efficiency.

2.1.4 Advancement of transport capacity by braking mode The train operation control System is a technical method to ensure the train running according to the space interval, and it is realized by controlling the train speed. The space interval between trains must be kept to meet the need of braking distance first, and of course, the appropriate margin of safety and the operation distance within the confirmation signal time should be considered. Therefore, different control modes are taken by train control system will produce different blocking system. Under the different block system, the smaller the distance between tracks, the greater the capacity.

32

2. High-speed railway signal technology and transport capacity

2.1.4.1 Hierarchical speed control (1) Multistep speed Multistep speed control is divided into lead and lag. The leading speed control mode is also called the exit speed control mode, which gives the value of the exit speed of the train and controls the train not to exceed the exit speed. Shinkansen ATC uses advanced speed control, as shown in Fig. 2.4. However, there are some disadvantages to this approach: first, because there is idle time when the brakes are released and applied at the speed limit, there is no reduction in the departure interval. Second, when the train reaches its maximum speed, it will be broken, which means less riding comfort. Third, if drivers want to run faster, they must replace all the associated wayside and on-board equipment. The lag speed control mode requires that the train speed be reduced to the target speed in the block and the equipment be checked at the exit of the block. If the actual speed of the train exceeds the target speed, the equipment will be braking. For example, TVM300, a train control system of CSEE corporation of France, is used on the Guangzhou-Shenzhen railway. The system uses a lag speed monitoring method to check only the speed entering the block section. Therefore, to ensure safety, it needs to have a protected section, which has an impact on the capacity of the line, as shown in Fig. 2.5[5]. The speed monitoring profile only controls the speed entering the block section with a straight speed monitoring line, and the driver controls the entrance speed to the next block section. In case of improper control will 300 275

Train Speed (km/h)

230

170 120 70 30 0

300

FIG. 2.4 Lead speed control.

275

230

170

30

33

Train Speed (km/h)

2.1 Train operation control system

0

FIG. 2.5

300

275

230

170

30

Lag speed control.

hit the monitoring profile of horizontal or vertical lines, resulting in emergency braking. If the train hits the monitoring profile within the last block, it will enter the next block, so the next block will be set as a protected section. (2) Curvilinear speed Curvilinear hierarchical speed control, each block section is given a speed control profile according to the train speed grading, the train speed control. The French TVM430 adopts curvilinear hierarchical speed control, although the TVM300 is quite suitable for 270 km/h on the Atlantic line with 4 min interval. But when the speed is increased to 320 m/h and the time interval is 3 min, the speed control system must be installed on the vehicle. And this speed control system is no longer based on speed classification, but on continuous profile braking [6]. The QinhuangdaoShenyang High-Speed Railway adopted the TVM430 train control system, which is not fixed at the entry speed of the section, but varies with the movement of the train to achieve the target speed at the exit, as shown in Fig. 2.6. Because the speed control is continuous, there is no need to add a block as a safety protection section, and only an appropriate safety distance should be considered in design. The length of the block is reduced to 1500 m compared to the multistep speed control. At any moment, the train data in the plan (distance, speed) are compared against a speed-control graph in the train-borne computer, this graph being based on the characteristic parameters of the train and information from TVM. Emergency braking is triggered when the curve on the graph is exceeded.

34

2. High-speed railway signal technology and transport capacity

F 320

F

F 320

F

F

300

320

F

230

270

300

F 170

F 000

F

red signal

speed limit area

270

230 170

320

320

300

270

230

flashing instruction

170

000

undetermined

1500m block section

block section marker

FIG. 2.6 Curvilinear hierarchical speed control.

2.1.4.2 Primary braking mode The East Japan Railway Company has developed a Shinkansen ATC using digital communication and control. The formal name is “DSATC” or digital ATC [7]. The digital ATC train operation mode is shown in Fig. 2.7 [8]. The system mainly relies on on-board equipment to control train speed, thus reducing the number of wayside equipment. The brake system changes from step to primary brake control, which improves passengers’ riding comfort and reduces the arrival time and the interval between trains. At present, the Chinese high-speed train control system Light braking force at first 300 Full service braking

275

Running pattern

Alarm 230

Train Speed (km/h)

Braking pattern 170 Lighter braking 120 Emergency braking

70 30 0 4

3 0 2 1 Number of clear track sections ahead

FIG. 2.7 Digital ATC train operation mode.

35

2.1 Train operation control system

adopts target-distance braking mode profile mode, which no longer sets a target speed for each block, but transmits the information of target speed and distance to the train. The speed is calculated by the on-board equipment according to the MA, the route data and the train performance parameters, and the target-distance braking mode curve is generated immediately when the train approaches the front deceleration point. The target-distance primary braking mode curve shortens the braking distance and gives different mode curves according to the train performance, which improves the transportation efficiency, as shown in Fig. 2.8 [9]. The ground equipment detects the current position and signal condition of the moving train and transmits the relevant information to the on-board equipment. From the database, the on-board device can check the braking mode profile of the single-level brake, control the train to stop at the target point, and compare the permitted speed and current speed of the train’s current position indication. If the train speed exceeds the allowable speed, the on-board equipment will output the braking command, causing the train to stop before reaching the target position. On the other hand, if the train’s speed falls below the allowable speed, it will issue a mitigation braking command. Normal braking will give an alarm when the train approaches the braking mode profile, and will start braking when it exceeds the braking mode profile. Target-distance primary braking mode is the smooth speed profile (including speed and distance) from the maximum speed of the train to the target point (stop point or speed limit point). Compared with the hierarchical speed control, the braking-relieving-braking-relieving process is reduced, and the variable braking force is used to realize the steady speed

Speed emergency braking speed profile service braking speed profile alarm speed profile actual speed profile

target location

0 Safe distance actual train speed

limit speed generation

route parameter

FIG. 2.8

information transmission

train performance

Target distance-velocity primary braking mode profile.

Distance

target point information acquisition

36

2. High-speed railway signal technology and transport capacity

control, which makes the driver easy to drive and the passengers comfortable. At the same time, in the case of multistage braking control, the frequency of low-speed driving tends to increase because the applied brake is released in stages. For the trains with primary braking system, speed is reduced faster than that with multistage braking system, the whole braking process is shortened and the running efficiency is improved. The American Advanced Train Control System (ATCS) was developed in the 1980s to achieve high-speed operation of trains and to reduce the intervals. In the mid-1990s, the United States developed the PTS [10]. PTS is only the first step in Harris’ plan to implement the communication-based train control system. The application of PTS has become the infrastructure of PTC system. PTC is an integrated system which integrates the subsystems of train command, control, communication and information to control train running safely, reliably, accurately and effectively. PTC system can improve the safety and efficiency of railway operation by reducing the probability of train collision, accidental injury and death of railway staff and equipment damage, as well as the occurrence of overspeed accidents. The system structure diagram is shown in Fig. 2.9 [11]. A broader version of PTC, called communications-based train control (CBTC), will bring additional security and commercial benefits to rail operators, such as real-time twoway communication at train locations combined with speed limits and MA, can improve the efficiency of dispatching, increase capacity and reduce fuel consumption [12]. PTC system strengthens the protection of maintenance workers. The high-speed crossing will also be connected to this control system which will also strengthens the management of operation and maintenance, thus improving the quality of passenger service and production efficiency. The ultimate goal of PTC system is to achieve moving block, shorten the train running interval, and manage more safe train operation. Wireless Data Link

GPS

Railway Staff Terminal

PTC Activated Intersection

Computer Aided Dispatch System

PTC Server

FIG. 2.9 PTC system basic structure diagram.

37

2.1 Train operation control system

PTC can reduce train intervals, congestion and delay, and has the outstanding advantages. With the application of PTC technology, the railway transportation capacity will be increased by 20% to 30%, and the PTS can control the train operation more accurately without adding track equipment and ground signal. In the future, wireless PTC may be used as the only significant signal system without the need for external blocking systems, or other devices currently in use in signal systems. PTC can provide a moving block around the train to provide sufficient separation which ensure maximum rail utilization. All signals will be displayed inside the locomotive. For a long time, PTC system has played an important role in keeping freight, passenger and commuter traffic flowing smoothly for national economy and citizen safety. In some ways, today’s PTC practices run counter to these goals, as they may stop or slow down trains prematurely or unnecessarily. These effects may be caused by abnormal events such as equipment/system failures, premature warnings or forced braking due to conservative braking algorithms, incorrect data, and operator errors. These events delayed trains and reduced capacity at a time when railways in many areas were nearing capacity limits. Transportation Technology Center, Inc. (TTCI), with support from the Federal Railroad Administration, researched a new mode of train control to increase operational efficiency where PTC equipment has been installed and is operational. TTCI developed a concept of operations (ConOps), safety analysis report, and an implementation and cost drivers analysis for an Enhanced Overlay Positive Train Control (EO-PTC)System. EO-PTC is intended to improve operational efficiency by eliminating signal-based speed limits in the block between the arrival and the advanced approach to the arrival when the onboard PTC is “Active,” as shown in Fig. 2.10.

Overlay PTC MAS=60MPH 30MPH

WIU

WIU

WIU

Restricted Speed

WIU

EO-PTC MAS=60MPH

Potential Gain 30MPH

WIU

FIG. 2.10

WIU

Speed limits with overlay PTC and EO-PTC.

WIU

Restricted Speed

WIU

38

2. High-speed railway signal technology and transport capacity

The EO-PTC concept can be safely implemented at minimal cost with no changes to on-board hardware or software. The efficiency gains over current PTC operations are most apparent in [13]: (1) Recovery from service disruptions where multiple trains have been stopped. (2) Scenarios where multiple trains queue waiting for departure from a yard or terminal. (3) Busy corridors or where train fleeting is used to reduce meets and passes, where reduced headways can result in incremental capacity improvements. 2.1.4.3 ERTMS(European Railway Traffic Management System) (1) Introduction Pressure continues to mount on Britain’s rail network. This seems to have become inevitable, starting with longer trains and increasing infrastructure capacity. Work is under way to improve the capacity of the Thames link across the north-south London route by improving the signaling system and adding tracks to the London Bridge River. A project to create a new east-west trans-railway line in London has been approved. ERTMS will have a major impact on the UK’s rail system and is expected to improve the safety and capacity of railways. ERTMS is a European Union-backed program that aims to improve interoperability and signal transmission across Europe by creating a single European standard. ERTMS has two main components: ETCS (European Train Control System): The technology means that speed limits can be transmitted to train drivers, and that their compliance with speed limits can be monitored on an ongoing basis. GSM-R (Global System for Mobile Communications-Railway): a radio system used to provide voice and data communications between tracks and trains, is based on standard GSM, uses frequencies reserved for railway applications, and has certain specific and advanced functions. ERTMS aims to replace many different European control and command systems to achieve a seamless European train system as a more competitive mode of transport. This would bring considerable benefits to the railway sector as it would facilitate international freight and passenger transport. The system can increase the capacity of existing lines and enhance the ability to cope with increasing transport demand: as a signaling system based on continuous communication, ERTMS reduces the distance between trains, 40% increase in the transport capacity of the existing infrastructure [14]. In short, it can increase current line capacity without massive infrastructure projects. ERTMS also allows for up to 500 km/h of high-speed service and should improve reliability and punctuality [15].

2.1 Train operation control system

39

(2) Categorize ERTMS ranges from the simplest level 1 to the most advanced level 3, as well as some hybrid versions for other markets [16]. For example, the UK’s Strategic Rail Authority and Rails Safety and Standards Board said the potential transport benefits of ERTMS 2D were “Significant” and “Could add up to 1/10th of a rail line” [17]. This article focuses on ERTMS levels 1 and 2. Table 2.1 compares different signaling systems. Fig. 2.11 shows the effects of different ETCS levels on transport capacity. (3) ERTMS and transportation capability ERTMS is similar to a conventional signal. However, differences, particularly in the ability to communicate, see more roads ahead and brake corners, have led to changes in infrastructure capacity. The following sections describe these parameters and their impact on capacity. Communications The difference in communication results in the discrete updating of the MA of the train driver at Level 1, and the continuous updating of the MA of the train driver at level 2 and Level 3. Position transfer and level 3 train integrity system are added to further allow application of moving block. This will result in a shorter separation between the two trains, as shown in Fig. 2.12. Blocking ERTMS offers the possibility of looking at more blocks than traditional signals. This is because electronic signaling systems are more modern, easier and cheaper than mechanical and relay signaling systems, and more blocks can be seen. In addition, ERTMS has cab signals to ensure that MA is displayed to the Driver on the cab’s Driver Machine Interface (DMI). Therefore, the number of signals that can be transmitted to the driver is no longer a limiting factor. In a traditional signaling system, only the first few blocks are visible, and the length of the them depends on the need to stop within the length of the block indicated to the driver. This limits how short the block of a traditional signal system can be. If the train cannot stop within a given signal range, the speed of the train will need to be limited. For ERTMS, where you can see more of the road ahead, which allows for shorter distances. Furthermore, it is no longer necessary to limit the speed due to the signaling system. This will lead to faster freight trains producing higher capacity and infrastructure on faster high-speed trains. (4) Level 1 vs Level 2 performance ERTMS level 2 has higher operational capacity than Level 1. It can be observed that most train combinations achieve significant increases in

TABLE 2.1 Comparison of different signaling systems. Conventional

Conventional multiaspect

Level 1

Level 2

Level 3

Train control

Possible

Possible

Included

Included

Included

Communication

Discrete (infill possible)

Discrete (infill possible)

Discrete (infill possible)

Continuous

Continuous

Signal aspects

2 (red/green)

3+

Movement authority

Movement authority

Movement authority

Signal visibility

Needed

Needed

Usually needed

Not needed

No signals

Train detection in track

Needed

Needed

Needed

Needed

Limit (on train and switches)

Train integrity

Not needed

Not needed

Not needed

Not needed

Crucial

Train position

Known in block section

Known in block section

Known in block section

Known in block section but can be more exact

“Exact” position known

41

2.2 Interlocking system Increase of capacity for the main line(ETCS level 1=100%) [%] UIC Code 406 137.7

139.6

135

115.0 115

110.8

104.3 100.0

101.6

103.1

104.6

109.9

95 Level 1 with optimized block section

Level 1 with limited supervision

Level 1 (service brake not available)

Level 1

Level 1 with a second infill balise(400m ahead of the main signal)

Level 2 Level 1 with infill loop service brake radio infill

Level 2 emergency brake

Level 2 with 400m block sections

Level 3

ETCS application configuration

FIG. 2.11

The effect of different ETCS levels on transport capacity [32].

FIG. 2.12

Headway at different speeds and levels of ERTMS.

capacity. The calculation model of headway is applied to the actual routes and timetables of freight, IC and high-speed trains. As shown in Table 2.2, the reduction of capacity consumption of level 2 trains and level 1 trains is limited to 1% to 10%, by an average of 3% [19].

2.2 Interlocking system 2.2.1 Introduction of interlocking system Safety and efficiency have been a major concern for the 1825 since the first railways were built in Britain. Railway signals appeared in 1830, the first mechanical interlock control equipment for the 1856 was born, and a relay interlocking system based on wiring logic was introduced in 1927.

42

2. High-speed railway signal technology and transport capacity

TABLE 2.2 Level 2 and level 1 capacity consumption comparison. Level 1

Level 2

Level 3

Line section 1

45%

44%

1%

Line section 2

46%

43%

3%

Line section 3

59%

49%

10%

Line section 4

50%

47%

3%

Line section 5

41%

39%

2%

Line section 6

56%

54%

2%

Line section 7

60%

59%

1%

Line section 8

61%

59%

2%

Line section 9

43%

42%

1%

Average

51%

48%

3%

The railway station interlocking system is a control system which is mainly used to control and ensure the safety of the operation of passenger, freight and shunting trains in the railway station, it is a typical safetycritical control system to realize important life-critical functions. Its basic function is to control the switch and lock of switch, the opening and closing of signal, the establishment and deblocking of route, etc. [20]. According to the interlocking relationship between signals (the basis of train operation), switches (which determine the direction of the train), track sections (which reflect the position of the train) and the route (which is composed of the relevant switches and track sections with signal indication and protection), the interlock condition is checked automatically on the operator’s operation, and the train and train operation are controlled through the arrangement of route and control signal display [21].

2.2.2 Improvement of transport capacity by interlocking system 2.2.2.1 Full mechanical interlocking Take London Greenford East Station as example, the operating arm in the signal room have different meanings for different colors: black is for switches, blue is for switch locks, red and yellow is for different types of signals, and white is for backup (unused). The interlock relation in the mechanical interlocking system is realized by the mechanical interlock bed. As the operating arm moves, the vertical tappet on the back side moves up or down. The horizontal arm is provided with a metal groove which can be inserted into a groove on one side of the vertical tappet. The

43

2.2 Interlocking system

action of an arm may drive one or more horizontal rods to move left or right. If any operating arm is not in the correct position and cannot be moved, the lever that needs to be operated will not be operated, which is rather cumbersome [22]. 2.2.2.2 Relay interlocking The appearance of electric centralized interlock, especially relay interlock, marks the beginning of railway station interlock from mechanical age to electric age. In order to meet the ever-increasing demand of railway transportation for speed and capacity, the electric centralized interlocking system has achieved all-round technical progress in the three elements of interlocking function (control, transmission and locking/deblocking), from wayside equipment to control system, the utility model effectively overcomes the shortcomings of the mechanical interlock, such as heavy and unwieldy, the limited control distance, the uneasy operation, the simply function, and the inconvenient maintenance, which are caused by the difficulty of transmission and locking. The function and control scope of the interlock system of the railway station have been enhanced significantly and comprehensively, the operational efficiency of the railway station has been effectively improved, and the working conditions have been greatly improved, greatly improves the station’s capacity as well as the accuracy and safety of traffic control, as shown in Fig. 2.13. (1) Relay interlocking logic circuit based on station ground graphic network and hierarchical structure. By adopting the circuit structure of 15 network lines corresponding to the signal plane diagram of station ground, and distributing the interlock functions of route selection, route arrangement, lock confirmation, open signal, deblocking and so Section manual release button panel

Relay assembly and

Distributing terminal board

Power supply panel

Control platform

Outside equipment

++

FIG. 2.13

Relay interlocking structure diagram.

+

44

2. High-speed railway signal technology and transport capacity

on between route operation and nonroute operation among different network lines, a complex sequential state machine system with complete structure, clear level, progressive function layer by layer and strict interlock logic is constructed. (2) Spliced standard shaped relay combination with high coverage of on-site equipment and station configuration. The design, production, installation, inspection, maintenance and repair of the interlock system in a specific station are effectively standardized and simplified, especially the structural mode of its type combination, which greatly increases the proportion of the production and preinstallation parts of the plant where the quality is more easily guaranteed, effectively reduces the design errors of the general circuit, and greatly reduces the workload of the field construction. (3) Apps are complex. Based on the idea that the standard system can be compatible with as many types of stations as possible and the demand situation, and in view of the common characteristics of mixed passenger and freight transportation and various operational requirements in China’s railway, the graphic network structure and basic circuits of station ground have gradually formed some special interface circuits and large-scale special functional circuits, such as the hump circuit of the Hump arrival ground, the plane single hook humping circuit and even the continuous humping circuit and so on. 2.2.2.3 Computer interlocking With the development of computer technology, especially the research on redundant fault-tolerant technology, the first computer interlocking system in the world came out at the end of 1970s—computer interlocking system used in Sweden Gothenburg station, countries have been developing and researching computer interlocking system, and have made remarkable achievements. The structure of computer interlocking is shown in Fig. 2.14. Compared with relay interlocking, on the one hand, the function of computer interlocking system is more perfect, which can be solved by a little hardware and software development in function expansion, and it can be connected with other train dispatching command system and train control system, provide and exchange all kinds of information. On the other hand, the computer interlocking system is easy to realize the system self-diagnosis, self-test function and remote networking, which is beneficial to the signal maintenance management and maintenance system reform. Among them, the application of new technology, new equipment has greatly improved the efficiency of railway transport, improve the working environment of staff, also improve the working efficiency and operational capacity, thus improving the railway transport capacity.

45

2.2 Interlocking system Control display A

Control display B

Maintenance machine

Optical communication network-I

Optical communication network-II External communication interface

External communication interface

Interlocking logic department

I system

I system PIO unit

II system PIO unit

II system

I system PIO unit

ET frame 1

II system PIO unit ET frame 2

Signal equipment

FIG. 2.14

Computer interlocking structure diagram.

Applying the TYJL computer interlocking system in Hudong station of Daqin Railway, the transport capacity of Daqin railway is increased to 100 million tons. Since the system has been put into operation, it has run smoothly and achieved good results, greatly improving the transport efficiency and working conditions.

2.2.2.4 Integration of train control and interlocking The SIMIS-W system belongs to another type of integrated train control interlocking system. Its interlock function includes not only interlock in station but also interlock in section. At the same time, the system can control the sending and receiving of the message of the active balise, provide the movement authority, and guarantee the safe operation of the train, achieve train control of ground equipment functions, thus improving the efficiency of railway transport, as shown in Fig. 2.15.

46

2. High-speed railway signal technology and transport capacity Train Control & Computer Interlocking Selfcontained System Architecture

Border TCC

ZPW

TSRS

LEU

RBC

Computer Interlocking

Train Control

Relay Interface

Balise

CTC

CSM

Border CBI

Train Control & Computer Interlocking Integrated System Architecture Border ZPW TSRS Balise RBC CBI

Train Control & Computer Interlocking Integrated System

Relay Interface

CTC

CSM

FIG. 2.15 Data transmission comparison of train control & interlocking independent and integrated setting.

(1) Reducing data interaction and improving communication efficiency Train Control Center and computer interlocking system are not completely independent, in order to achieve related functions, the two systems need to carry out a lot of data interaction in each communication cycle, the degree of coupling between the two systems is very high. After the integration of train control and interlocking, it is only necessary to transfer the relevant data directly in the system, which will effectively improve the efficiency and accuracy of the system. In addition, the integrated system can change the complicated interface information transmission process into the internal data processing, so that the key operating data of the system can be shared internally, which is helpful to improve the utilization rate of data and reduce the complexity of software development, improve real-time performance of the system [23]. (2) Intelligent maintenance and shorter fault recovery time The system can collect and record the equipment status information in the station and the section, the operating status of the integrated system, the communication status of the interface with the peripheral equipment and so on. Through the acquisition of station and section maintenance information, data analysis, the system will have more perfect functions of fault prediction, diagnosis and analysis. The integrated maintenance terminal is set up to remotely monitor the operation status of each station, providing functions such as multilevel check, replaying, management and fault handling, which is helpful for maintenance personnel to quickly judge the faults in a short time, to provide more precise technical support, greatly reducing the fault response and processing time. 2.2.2.5 Digital computer interlocking The interlocking system adopts cable to connect indoor and outdoor equipment, and transmits the strong current of indoor power panel to outdoor equipment by controlling the weak current. All-digital computer interlocking will be the next development stage of computer interlocking and a revolution of computer interlocking. It is a new type of computer

2.3 Dispatching command system

47

interlocking system based on wireless communication, intelligent outdoor equipment and no cable connection with indoor and outdoor equipment. The outdoor equipment only needs the power supply of the distributed power supply terminal, and communicates with the interlock processing device through the security communication protocol. The 2018 Siemens project report speaks of a digital revolution in the German rail network: Europe’s first digital interlocking system, DSTW, launched by Deutsche Bahn AG, is already operating in south-eastern Germany [24]. The new interlocking structure is characterized by the transfer of dispatchers’ switching commands to points, signals, and track by network technology. As a result, the previously required portion of the interlock component connected to the individual interlock components through a kilometer-long cable bundle has been eliminated. Now, signals can be controlled at greater distances by data lines and DSTW network contacts. In the process of traffic transformation and climate protection, German railways insist on the premise of improving efficiency. Digitalization will make a decisive contribution to this. Digital interlocking is integrated with Europe-wide standardized train control system ETCS to intelligently network all data in infrastructure and trains. They have launched a new railway operation organization for all companies. Intelligent communication network and its related standardization and modularization technology are leading the trend in the next few years. They enable German railways to operate rail transport more economically, while saving customers resources and ensuring greater efficiency. Therefore, the new interlocking technology is a milestone in the digitization of railway infrastructure and will be the basis for improving railway transport capacity and punctuality.

2.3 Dispatching command system 2.3.1 RCS (railway control system) RCS is a new generation dispatch and command system independently developed by SBB company, and it is the result of self-developed with the support of OCC project. In the aspect of Operation Organization and Dispatching Command, the advanced digital technology is fully utilized to realize fully automatic conflict detection and train operation adjustment, which greatly improves the transport capacity and reduces the train operation delay. According to Swiss railway statistics, the departure interval of a local station turning back section (such as platform 40–44 of Zurich station) can be compressed to 2 min after RCS is put into operation, a total of about 2000 min of train delays per month can be reduced in the Zurich station area, which is equivalent to a reduction of 1.2 million minutes of passenger delays. It makes Swiss railway becomes the most highly rated railway network in Europe [25].

48

2. High-speed railway signal technology and transport capacity

2.3.2 TMS (traffic management system) The EBICOS TMS system of ABB Signal, a Swedish company, is the basis of its integrated railway traffic management system, which allows the exchange of information between different stations and systems using standard communication protocols. With TMS’s help, the West Mumbai Suburban railway line is excellent in punctuality and safety, handling nearly 1000 trains a day. Using TMS, traffic controllers will be able to monitor some of the densest lines in real time. After each successive 3-min interval, the system will manage the trains arriving at each station. In case of interference, the system will also provide the information needed for rapid decision-making [26].

2.3.3 CTC (centralized traffic control system) The future operation of China’s high-speed railway, as shown in Fig. 2.16, includes two aspects: operation planning establishment and adjustment [27]. Comparing the existing scheduling with the intelligent scheduling, the intelligent CTC is transformed from the “Artificial experience Network Planning

Strategic Layer Passenger Demand Analysis Feedback

Passenger Demand Analysis

Network Planning Train Operation Plan Design

Transportation Resource Allocation

Modification cycle: month/year Train Operation Diagram Organization

Train Operation Plan Design

Tactical Layer

Feedback

Train Operation Diagram Organization

Station Operation Plan

Existing Dispatch

Distributed Iterative Organization

EMU Operation Plan

Integrated Organization

EMU Operation Plan

A Intelligent Diagram Dispatch A Day

Station Operation Plan

Flight Attendant Scheduling Plan

Flight Attendant Scheduling Plan

Modification cycle: week/month Daily Dispatch

Daily Dispatch

Manual Experience

Machine Learning, Decision Supervise

Train Depot

Telephone

Telephone

Locomotive Depot

Telephone

Vehicle Depot

Electricity Services Department

Operational Situation Awareness

Train Depot

Public Works Section

Operation Layer

FIG. 2.16

Feedback

Intelligent Decision

Locomotive Depot

Public Works Section

Vehicle Depot

Electricity Services Department

Comparison between existing dispatching and intelligent dispatching.

2.3 Dispatching command system

49

passive response” to the “Scientific and efficient active regulation,” in the event of unexpected incidents resulting in traffic disorder as soon as possible to restore traffic order. The intelligentization of the system can further improve the transport capacity, improve the service level and reduce the operation cost. With the completion of the new generation CTC, the jurisdiction of the dispatching section can be extended to about 500 to 800 km. Combined with the reform of China’s railway transportation system and the adjustment of productivity distribution, it can greatly reduce the number of on-site traffic operators, improving the efficiency of railway transportation, and the CTC annual investment recovery rate is expected to reach about 30%. With the development of American railway transportation and the change of market demand, the CTC technology of American railway is also developing constantly. The operation and command of BNSF company in Santa Fe, north of Burlington, is based on the model of highly centralized operation and management. The 52,300 km railway under the jurisdiction of BNSF company is operated by a centralized operation and command center. The 34,000 km of the line is controlled by the centralized traffic control, and the remaining line is nonsignal and noncentralized control section. So, the proportion of centralized control is 65%. BNSF has established three regional dispatch control centers in Kansas (KC), California (SAN) and Houston (SP) in 1997,1998 and 2000, each of which controls about 200 km of lines, under the lead and unified command of head office dispatch, carrying out the plans and orders issued by NOC center, strengthening the coordination work with other companies’ dispatch, improving the transportation efficiency and customer satisfaction. BNSF centralized dispatch command mode is shown in Fig. 2.17 [28]. The United States is gradually transforming and obsoleting CTC equipment built in the 1980s and early 1990s, and gradually transforming it into an intelligent, systematic and integrated dispatching and command system. CTC from the Unite States railway technology development direction, there are the following major transport capacity improvements. (1) Intelligence, systematization and integration. The planner of the NOC center uses the transportation decision support system (TSS) to make the train operation plan, locomotive and train crew operation plan, station line operation plan and marshaling station operation plan 9 to 10 days in advance. The plan is transmitted to the computer aided dispatch system (CAD) through the local area network (TMDS). The dispatcher uses the CAD system to make the 48-h plan and the construction plan. According to the daily schedule and the actual situation of the train operation, the train dispatcher makes a 4- to 6-h train operation phase plan. According to the daily schedule and the actual situation of the train operation, the train dispatcher makes a 4-

50

2. High-speed railway signal technology and transport capacity

Network Operation Center(NOC) 85 Channels

Houston Region Dispatch Center 5 Channels

FIG. 2.17

Wired/Wireless Communication Network

California Region Dispatch Center 10 Channels

Kansas Region Dispatch Center 11 Channels

Topcka Disaster Recovery Center

BNSF company dispatch centralized command center schematic.

to 6-h train operation phase plan. The plan is transmitted to the station ground computer interlocking system via a dedicated wired and wireless network to remotely control the train to run as planned. CTC system information flow diagram is shown in Fig. 2.18. (2) The marshaling station adopts a separate dispatching control mode and can exchange information with CTC. Based on the interface between marshaling station automatic system (Yard) and CTC, CTC transmits the actual running situation of trains arriving and departing on main line to Yard, Yard can monitor the running situation of trains on main line in real time to ensure the running and dispatching command of trains. (3) CTC construction mode and investment benefit. CTCS cost about $150,000 per mile in the United States. CTC can partly improve the transport capacity, improve the safety of train operation, improve transport efficiency, and reduce a large number of on-site operation personnel. The investment benefit is very obvious. (4) CTC systems are equipped with two sets of equipment. The dispatching command center has set up a standby dispatching center in different places, with two machines on standby and real-time data on standby. Automatically switch to the backup system when the equipment in the dispatch center is unable to command. The conversion time between the two systems is less than 5 min to ensure the normal operation of the transportation command.

51

2.3 Dispatching command system Flight Attendant Information Train Height Limit Information Train Schedule Other Train Information

Train Suspension Transportation Decision Support System

Line speed limit

Wired/Wireless Communication Network

Train Formation

Line Authorization

Dispatcher Input Train Position

Computer Aided Dispatch System

Wired/Wireless Communication Network

Train Tracking and Positioning Train Running Late

Equipment Status

Computer Interlocking System

Remote Control

FIG. 2.18

Remote Control

CTC system information flow diagram.

2.3.4 STEG (STyrning via Elektronisk Graf, in Swedish) The trains of the future will need faster speeds, more frequent traffic, mixed traffic and many independent transport operation companies [29]. Therefore, new principles and technical solutions are needed to achieve effective train traffic control. Today’s control systems are typically designed to support operator responses to alerts, conflicts, and disturbances and to address the likelihood of serious problems and conflicts, as shown in Fig. 2.19. However, in order to perform the operation efficiently, the traffic officer should be able to track the dynamic process of the traffic system over time and prevent interference. To achieve this goal, we must change the control paradigm from technical control of the infrastructure to a higher level of transportation planning tasks. This can be done by replacing the traditional control commands with real-time planning, as shown in Fig. 2.20 [30]. The Swedish Banverket decided to develop and deploy an operational system to be installed in the traffic control center. The system, called STEG, applies the main findings. The new system features a dynamic planning view in the form of a time-distance diagram to help traffic officers identify disturbances and conflicts, as well as an automated system for carrying out traffic plans. A traffic officer can replan traffic (time, track usage), track maintenance, and other activities directly by manipulating the lines in the

52

2. High-speed railway signal technology and transport capacity

Information Systems

Time-Distance Graph on paper

Train Dispatcher

Surroundings

Control System

Train Traffic Process

FIG. 2.19

The current strategy model.

New user interface Computer based time-distance graph Track diagram Automatic execution function

Train Dispatcher

Surroundings

Real-time database

Train Traffic Process

FIG. 2.20

New control strategy model.

interface. STEG is designed to provide an efficient user interface and better decision support to keep train conductors up-to-date and to assess, act on and prevent potential future traffic conflicts. The control concept also provides the basis for more effective sharing of the latest traffic plans and information with relevant colleagues, as all colleagues have access to this information [31]. STEG’s design is in line with the new control mode to better support the train Operation Controller to perform the task, the user interface is shown in Fig. 2.21 [32]. STEG was actively deployed in the first train traffic control center and it was decided to further develop STEG into a multi-STEG for use by multiple train traffic controllers in adjacent geographical traffic areas. The advantage of multi-STEG is the possibility of sharing information. Together with MULTI-STEG, another system called CATO (Computer

2.3 Dispatching command system

FIG. 2.21

The STEG user interface.

FIG. 2.22

The connected driver advisory system CATO.

53

54

2. High-speed railway signal technology and transport capacity

Aided Train Operation) was developed, as shown in Fig. 2.22 [32]. The CATO is designed to be used by train drivers to keep up-to-date on changing transport plans. The assessment showed a 25% probability of energy-saving, providing a punctuality rate of about 10% and providing an example of how the train would fare if it followed the plan received from STEG, significantly reduces the need for traffic controllers to adjust their traffic plans. In northern Sweden, all traffic on the iron ore route is controlled by STEG and the train is fitted with a C-DAS CATO. So far, the results have been encouraging. STEG has received a positive response from traffic officers and its concept will be the basis for the introduction of new traffic control systems throughout Sweden. CATO show that the Real-Time Traffic plan (RTTP) can reduce energy consumption, improve on-time rates, and reduce traffic managers’ re-planning efforts.

References [1] X. Kai, M. Zhang, L. Wang, Development and research of railway block technology, Railw. Signal. Commun. 55 (S1) (2019) 60–67. [2] Q. Liang, Shuohuang Railway Heavy Haul moving block technology to achieve a major breakthrough, World Railway 7 (2021) 44–45. [3] Y. Zhang, J. Wang, Z. Chen, Y. Xiaona, Main functional features of on-board equipment of automatic CTCS-3 train control system, Railw. Signal. Commun. Eng. 15 (02) (2018) 6–11. [4] R. Zhang, The present situation of railway signal at home and abroad, the contrast of difference and the thinking of the development direction of railway signal in China, Railw. Standard Des. 07 (2004) 117–120. [5] S.S. Fu, Fundamentals of railway signaling part 3: choice of quasi-move block, Railw. Signal. Commun. Eng. 8 (05) (2011) 76–79. [6] J.P. Guilloux, Train control on French railroads, Transp. Res. Rec. (1991) 1–5. [7] T. Igarashi, T. Sato, Y. Harima, et al., Digital Automatic Train Control System for the Shinkansen Lines of East Japan Railway Company, Computers in Railways VIII, 2002, pp. 83–92. [8] T. Takashige, Signalling systems for safe railway transport, Jpn Railw. Transp. Rev. (1999) 44–50. [9] W. Shangguan, B.G. Cai, J.J. W, et al., Braking mode curve arithmetic of high-speed train above 250 km/h, J. Traffic Transp. Eng. 11 (3) (2011) 41–46. [10] S. Li, J. Mao, Automatic train control development from ATCS to PTC, Chin. Railw. 01 (2001) 53–55. [11] L. Cai, L. Zhao, C. He, Overview of American PTC system, Railw. Signal. Commun. Eng. 7 (03) (2010) 24–27. [12] J. Frittelli, Positive Train Control (PTC): Overview and Policy Issues, CRS Report for Congress, 2012, pp. 1–17. [13] J. Brosseau, C. Grimes, M. Oztekin, et al., Development of Enhanced Overlay Positive Train Control (EO-PTC), United States, Department of Transportation, Federal Railroad Administration, 2019. [14] https://www.railway-technology.com/projects/european-rail-traffic-managementsystemertms/.

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[15] https://aslef.org.uk/support/industry/european-rail-traffic-management-system. [16] R. Vergroesen, ERTMS/ETCS Hybrid Level 3 and ATO: A Simulation Based Capacity Impact Study for the Dutch Railway Network, Master Thesis, Delft University of Technology, Transport and Planning, 2020. [17] W.A.M. Barter, ERTMS level 2: effect on capacity compared with\“best practice” conventional signalling, WIT Trans. Built Environ. 103 (2008) 213–222. [18] UIC, Influence of ETCS on line Capacity – Generic Study, UIC, 2008. https://uic.org/ cdrom/2011/05_ERTMS_training2011/docs/Capacity-generic-study.pdf. [19] A. Landex, L.W. Jensen, Infrastructure capacity in the ERTMS signaling system, RailNorrk€ oping, in: 8th International Conference on Railway Operations Modelling and Analysis (ICROMA), Norrk€ oping, Sweden, June 17th–20th, 2019, Link€ oping University Electronic Press, 2019, pp. 607–622. 2019 (069). [20] H.X. Lin, X.Q. Zeng, T. Shen, et al., Research on development of interlocking technology for high-speed railway, Chin. Railw. 04 (2016) 38–43. [21] W. Duan, Overview of railway stations of interlocking development in China, Railw. Signal. Commun. 55 (S1) (2019) 86–97. [22] L. Huang, The past, present and future of railway interlocking system, in: 2020 IEEE 5th International Conference on Intelligent Transportation Engineering (ICITE), IEEE, 2020, pp. 170–174. [23] C.X. Jia, H.T. Zhang, Z.H. Qi, Development trend of interlocking and train control system of China railway, Chin. Railw. 02 (2020) 1–5. [24] https://www.deutschebahn.com/de/presse/pressestart_zentrales_uebersicht/DBsetzt-Digitalisierungsoffensive-fort-Kuenftig-steuern-280-digitale-StellwerkeZugverkehr-in-Deutschland-4578022. [25] T. Tang, K.C. Li, S. Su, et al., Characteristics of SBB traffic control system and its inspirations, Chin. Railw. 11 (2019) 18–23. [26] https://www.firstpost.com/business/biztech/tms-to-provide-minute-by-minutearrival-update-to-commuters-1866935.html. [27] B. Ning, Z.S. Mo, K.C. li, Application and development of intelligent technologies for high-speed railway signaling system, J. China Railw. Soc. 41 (03) (2019) 1–9. [28] Ministry of Railways to Centralized Traffic Control Reconnaissance Mission, Investigation report to the centralized traffic control by the Ministry of Railways, Railw. Econ. Res. 03 (2005) 19–24. [29] B. Sandblad, A.W. Andersson, A. Kauppi, G. Isaksson-Lutteman, Development and Implementation of New Principles and Systems for Train Traffic Control in Sweden (Computers in Railways XII), WIT Transactions on the Built Environment: Computers in Railways XII, 2010, pp. 441–450. [30] A. Kauppi, J. Wikstr€ om, B. Sandblad, A.W. Andersson, Control strategies for managing train traffic—difficulties today and solutions for the future, Technical Report 2006-24, 1404-3203, Department of Information Technologyat Uppsala University, 2006. [31] G. Isaksson-Lutteman, Future Train Traffic Control: Development and Deployment of New Principles and Systems in Train Traffic Control (it licentiate theses), 2012. [32] S. Tschirner, B. Sandblad, A.W. Andersson, Solutions to the problem of inconsistent plans in railway traffic operation, J. Rail Transp. Plan. Manag. 4 (4) (2014) 87–97.

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C H A P T E R

3 Improving transport capacity by increasing the information amount of Chinese train control system 3.1 Expanding route information to improve transport capacity 3.1.1 Improving transport capacity by signal display development From the 1825, the world’s first British Stockton railway put into operation, people used signal delay, black and white ball, telegraph, railway semaphore signal, track circuit, color light signal, locomotive signal, and other ways to transmit signals and command drivers to drive the train. With the increase of train speed and density, the signal display technology is being improved and upgraded to ensure the safety and efficiency of train operation. With the increase of train control information, the transport capacity of the railway line is constantly improved. Train control information related to line capacity includes signal information, train speed, route length, turnout number, block length, line data, train data and so on. 3.1.1.1 Introduction of color light signal Color signal can be used for the arrival, departure, route, shunting, passing, blocking, protection, hump, warning, repeating and guiding signal and so on. The color signal is used to indicate the allowable speed and route information of the train. Signal display is divided into route mode, speed-different mode and speed mode. Route mode is a signal display system based on the principle of indicating trains to enter different routes. The signal indicates a definite train route, but does not contain a definite

Theory and Technology for Improving High-Speed Railway Transportation Capacity https://doi.org/10.1016/B978-0-323-99700-3.00010-4

57

Copyright © 2023 Elsevier Inc. All rights reserved.

58

3. Improving transport capacity

speed limit, and the presence of several red and green lights on the same signal can cause confusion. Therefore, the route mode is only suitable for low-speed trains, the driver will ensure the safety of the train. The speed differential mode specifies the number of displays and the method of display, depending on the required speed limits. The speed mode is a signal system which shows the profile characteristics of the speed target distance pattern by train control on board equipment, which provides more signal information than the route mode and the speed differential mode. China has adopted speed differential mode and speed mode. The advantages of integrated route mode, speed differential mode and speed mode are the development direction of signal display system, aiming at further improving the safety and efficiency of train operation. Table 3.1 is the Chinese train speed and signal information table. The interval distance is the sum of the train running distance in the system response time and the emergency braking distance after the official start. For example, the emergency braking distance for trains running at 350 km/h is 6500 m, while the train operating distance for the system confirmation phase is 7000 m, which adds up to 13,500 m. This distance corresponds to the length of the block section which requires eight information codes. It can be seen that with the increase of train speed, train control information is also increasing.

3.1.1.2 Evolution of signal display The main function of signal display is to give instructions through signal machine, in order to achieve the train speed to adapt to the line, keep a safe distance from the obstacles in front or meet the operating interval. With the increase of driving speed level, the number of driving signal TABLE 3.1 Chinese train speed and signal information table. Signal information code

Number and spacing of idle block section

Block section (m)

Threeaspect

H, U, L


2

1600

800

1100

Fouraspect

H, U, LU, L


3

3600

1000

250

3200

Sixaspect

H, U, LU, L, L2, L3


5

8400

1000–1200

350

6500

Eightaspect

H, U, LU, L, L2, L3, L4, L5


7

13,500

2000–2400

Train speed (km/h)

Braking distance (m)

> < Ndj ¼ K (4.15) > ndf > : Ndf ¼ K

120

4. Influence of variable approach locking section rules

where Ndj and Ndf are the capacity of receiving-departure in d direction. ndj and ndf are the number of receiving-departure in d direction. Similar, the practical utilization ratio of passing capacity of the arrivaldeparture track K is: X tx  tg K¼ (4.16) X  TM  tg ð1  αÞ So the capacity of receiving-departure of all directions Nd is: Nd ¼

nd K

(4.17)

Shaoguan Station of China Beijing-Guangzhou high-speed Railway that the design speed is 350 km/h. In the daily operation plan of Shaoguan Station, there are 26 trains of 160 to 250 km/h and 93 trains of 250 to 350 km/h through Shaoguan station 1 day, and the type of CTC is FZkCTC. The plane layout of signals and length of downward positive block sections are shown as Fig. 4.6 and Table 4.1. To simplify the calculation, the control system was assumed to be CTCS-3. All trains passing Shaoguan station were considered to be CRH3C, the rotational mass coefficient of which is r ¼ 0.1, tc ¼ 26.8 s, and tk ¼ 1.5 s. Tables 4.2 and 4.3 show the space trigger timing and the train’s downward approach section length at different speeds after the application of variable approach section mode and the comparison with the original fixed approach section mode in Shaoguan station. As can be seen from the table, for trains running at low speed, using variable approach section mode can significantly delay the route Shaoguan station K2067-257

5G

13

3G 11 1

7 9

3

X3

18

G

X

G

X

16 8

2

SF

S

15 XF

20

S3

Downward X

X5

S5

10

S

5

4G

17

X4 12

S4 6G 19

X6

S6

FIG. 4.6 The plane layout of signals of Shaoguan station.

14

6

4

Upward

S

121

4.1 Improving station capacity by variable approach locking section rules

TABLE 4.1 The length of downward positive block section of Shaoguan station. Block section

L1

L2

L3

L4

L5

Length (m)

1663

1279

1818

1801

1832

Block section

L6

L7

L8

L9

L10

Length (m)

1860

1823

1874

1788

1810

Block section

L11

L12

L13

L14

L15

Length (m)

1852

1850

1876

1828

1948

TABLE 4.2 The downward variable approach locking section of Shaoguan station.

Rounding distance (m)

Variable approach section distance (m)

The number of block sections

110.00

484.8

2939

2

1415.00

110.00

1767.99

4757

3

2524.05

1729.44

110.00

393.51

4757

3

250

3506.49

1965.28

110.00

976.23

6558

4

300

5479.05

2358.33

110.00

442.62

8390

5

320

6391.18

2515.56

110.00

1233.26

10,250

6

350

7897.96

2751.39

110.00

1313.65

10,250

7

Speed V (km/h)

Active braking distance (m)

Braking transmission distance (m)

Additional safety protection distance (m)

160

1086.42

1257.78

180

1464.01

220

TABLE 4.3 The space triggering time of downward positive route for receiving trains of Shaoguan station. Speed V (km/h)

The length of variable approach section

The length of fixed approach section

Trigger time for fixed approach section

Trigger time for variable approach section

230–249

4

8

15

4

250–307

5

8

15

5

308–333

6

8

15

5

334–340

6

8

15

6

341–350

7

8

15

8

122

4. Influence of variable approach locking section rules

processing time and shorten the approach section length. For trains running at 250 to 269 km/h, the approach processing time is delayed by seven block sections, and the approach section length is shortened from 8 to 4. Fig. 4.7 shows the relationship between the time saved and the speed by using the variable approach segment mode. The faster the speed, the less time saved. The relationship curves between station passing capacity and speed in two modes are described in Fig. 4.8. The blue curve is the

FIG. 4.7 The saving time of one routing of variable approach locking section.

FIG. 4.8 The comparison of passing capacity in both conditions.

4.2 Optimizing operation of station

123

relationship between station passing capacity and speed in fixed approach lock mode. The faster the speed is, the higher the station passing capacity is. The red curve is the relationship between the station passing capacity and the speed under the variable approach section mode. The passing capacity generally remains at a high level, while the passing capacity decreases when the speed is high.

4.2 Optimizing operation of station After more than 10 years of development and the application of new technologies such as wireless communication, the rail capacity has been greatly improved. The CTCS-3 train control system has shortened the headway to 3 min. Limited by the existing station organization the improvement of station passing capacity is not obvious, which has become an important restricting factor of high-speed railway passing capacity [12]. This section describes how to improve station passing capacity by optimizing station operation.

4.2.1 Station operation refined management The operation of the train in the station can be divided into receiving and dispatching operation and shunting operation. The interlocking system manages track circuit, switches, and signals and divides them into multiple units [13]. Taking track circuits, linkage turnouts and invading insulation joints into consideration, station resources are divided into minimum occupancy units according to interlocking rules and a route is consists of multiple minimum occupation units. On the basis of the minimum occupancy unit, the composition of train occupancy time is analyzed to realize the accurate station interval time and the efficient control of route resources. Based on the accurate calculation of station interval time, the passage capacity is strengthened by the segmented open approach mode. Dividing the minimum unit occupied is the premise to realize the segmented opening of the route, and its dividing method is related to the track circuit switches in the approach and the arrangement of intrusion insulation joints [14]. (1) Track circuit. If the station interlocking relationship is not considered, the minimum occupancy unit in the station is the track circuit separated by insulation joints. (2) Turnout. Single-action switch complete is included in a route. But there are two sets of double-action switch, which belong to different track section, respectively. Therefore, in the division of occupancy unit, the layout of double-action switch must be considered. When all

124

4. Influence of variable approach locking section rules

switches of the double-action switches are within the route range, the track circuit in the turnout section should be regarded as a minimum occupancy unit. When only one set of double-action switches is within the route range, the track circuit in the turnout section of the two sets of switches should be regarded as a minimum occupancy unit, respectively. (3) Invading insulation joints. Fouling post is set in the middle of 4 m distance between the two rendezvous lines to prevent side conflicts between trains. In severe surroundings, if the distance between the insulation joints and the fouling post cannot meet, the insulation joints is named as invading insulation joints. When the train stops inside the invading insulation joints, other trains passing along the adjacent line may cause side collision. So, when the train passes through the track circuit on both sides of the invading insulation joints, the track circuit on both sides should be regarded as a minimum occupancy unit in order to ensure driving safety, when the train only passes through the track circuit on one side of the invading insulation joints, the track circuit on both sides is regarded as a minimum occupancy unit. As shown in Fig. 4.9, block time include: setting route time, reaction time, approach time, Running time, clearing time, and unlocking time [15]. Setting route time is the time consumed by the station in the process of setting route. Reaction time is the time spent in vehicle-ground communication and driver confirmation signals. Approach time refers to the running time of the train from the approach warning point to the protection signal in the block section. Approach warning point refers to the point at which the rear car can reach the entrance of the block section under the premise of not affecting the normal running speed, which is jointly determined by the braking performance and running speed of the train.

Block section Route setting time Reaction time Approach time Running time Clearing time Unlocking time

FIG. 4.9 Block time of the train.

4.2 Optimizing operation of station

125

The running time is the time it takes for the train to pass through the block section. Clearing time refers to the time required for the train to completely clear the train to occupy the smallest unit. Unlocking time refers to the time it takes to unlock a route in sequence with the closed signal. As a result of the station organization rules, when the train clears all the route in other trains can occupy the route resources and establish train route, which is holistic open mode. As shown in Fig. 4.10A, because the front train has not cleared all route, the MA of the rear train can only be opened to the front of the minimum occupying unit 1, resulting in a long distance between the approach point and the minimum occupying unit, and the approach time of the train in the minimum occupying unit 3 and 4 is too long. Segmental open mode refers to the arrangement when the train route, don’t need all track circuit are idle, only check the switch position and the rail can be manipulated to correct position, and there is no hostile route is established. Train terminate occupancy minimal footprint within the station unit, after the other train instantly can begin to take up the unit. As shown in Fig. 4.10B, after the current train clears the minimum occupancy unit of the train, the following train can immediately occupy the unit,

minimum occupancy unit 1

a b c d e f

minimum occupancy unit 2

a b c

minimum minimum occupancy unit 3 occupancy unit 4

a b c

d e f

a b c d e f

minimum occupancy unit 2

a b c

d e f

e e f

minimum minimum occupancy unit 3 occupancy unit 4

a b c

d d e f

a b c d

d

(a) minimum occupancy unit 1

a b c

minimum occupancy unit 5

e f

a b c

f

minimum occupancy unit 5

a:setting route time b:reaction time c:approach time d:Running time e:clearing time f:unlocking time

a b c

d

d

e f

e f

(b)

FIG. 4.10 The change of minimum train interval time: (A) holistic open mode (B) Segmental open mode.

126

4. Influence of variable approach locking section rules

shortening the approach time of the minimum occupancy unit 3 and 4. After the segmentalized open mode is adopted, the utilization efficiency of station resources is improved, and the tracking interval between trains is also shortened.

4.2.2 Optimization method of departure interval The train departure tracking interval is the interval between the departure of the first train from the station and the departure of the second train in the same direction [16,17]. EMU depart in CTCS-2 partial supervision mode or CTCS-3 full supervision mode. If the length of firstly departure section meets the length required for the train to slow down to stop at the lateral speed limit of the switch, as long as the front train clears the firstly departure area, it can set the departure route for the rear train. In the existing high-speed railway station departure mode setting the departure route for the rear train, the firstly departure route must meet the requirement that the length of firstly departure section can ensure that the train slows down to stop at the lateral speed limit of the switch and the forward train clears the firstly departure section. Preprocessing departure section means that, after the current train clears out of the station and reverses the entrance signal, it immediately handles the departure approach for the rear train. As shown in Fig. 4.11, after the departure route is completed, the exit signal will not be opened. After the current train clears the departure area, the departure signal is opened, and the rear train starts the departure, the departure time of the rear train can shorten [18].

traditional The forward train clear signal

optimization

The forward train cleared the first departure section

Setting the departure route

Open departure signal

ΔT

Train Start

FIG. 4.11 entry.

Train departure tracking interval time compression in the case of predeparture

127

4.3 Integrated traffic management with station signal system

4.3 Integrated traffic management with station signal system 4.3.1 Traffic conflict resolution method As is shown in Fig. 4.12A, railway traffic management across Switzerland networks is hierarchically structured according to functional purposes [19]. At the dispatching level traffic management system supervise the railway network in real time, predicts the running status of trains. Dispatchers make dispatching decisions based on monitoring information and send dispatching orders to remote traffic control center by phone. Remote traffic control center control trains by setting their routes and issuing speed limits through signals. Fig. 4.12B is the interface of dispatchers in Switzerland railway and Fig. 4.12C is the on-board equipment. In such a hierarchy, the reliability and rationality of dispatching decisions depend on the professional level of dispatchers. In addition,

Traffic management center

Dispatching

Traffic management center

Centralized traffic control center

Centralized traffic control center

Remote traffic control

Interlocking Block

Train/Signal System Infrastructure Equipment

Interlocking signalling

Interlocking signalling

signal track circuit turnout

signal track circuit turnout

(a)

RTM Profi bus

LKJ

RS-422 CCU3

CCU2

SPU TIU

TCR

TCR

BTM

DMI

Driver

CAU

(b)

(c)

FIG. 4.12 (A) Structure of railway traffic management, (B) interface of dispatchers in Switzerland railway [19], (C) on-board equipment [20].

128

4. Influence of variable approach locking section rules

dispatching orders have to pass through traffic control centers and must be converted into executable route information and speed limit information, which slows down the control process. Meanwhile, the execution effect of dispatching decision depends on the driver’s experience and professional level [21]. Therefore, traffic control centers are merged with traffic management to speed up the control flow to the operational level [22]. At the same time, dispatcher decision advisory system is introduced to assist dispatchers to predict and solve traffic conflicts, and driver decision advisory system is introduced to assist drivers to correctly execute dispatching decisions and smoothly control trains, as shown in Fig. 4.13[23].

FIG. 4.13

The structure of traffic management.

4.3 Integrated traffic management with station signal system

129

Dispatcher advisory system is divided into two types: Dispatcher support system for dispatcher (DSS) is set in the traffic management center, mainly through generating control suggestions to dispatcher to solve traffic conflicts. Driver advisory system for dispatcher (DAS-C) is a driver decision advisory system set up in the traffic management center. It provides train speed suggestions for drivers, notifies drivers to reduce train speed when conflicts are detected, and notifies drivers to increase train speed after conflicts are resolved, so as to reduce unplanned stops of trains. Driver advisory systems is also divided into two types: Driver Advisory System-Onboard (DAS-O) is set on the train, which provides speed suggestions to the Driver but its purpose is to improve the driving behavior of the train: improve driving accuracy, energy saving, and other optimization objectives. Automatic Train Operation (ATO), which generates a series of train control commands to directly control the speed rather than providing speed suggestions to the driver. Table 4.4 lists the characteristics of DSS, DAS-C, DAS-O, and ATO. Train conflict refers to the mutual restraint between two trains that need to use the same technical equipment at the same time. As shown in Fig. 4.14, two trains are running in opposite directions. The red dotted line is the running route of train 1, and the blue dotted line is the running route of train 2. The slow speed of train 1 leads to an unplanned stop of train 2, so the operation process of train 2 needs to be optimized. As shown in Fig. 4.15, traffic control using DSS DAS-C, DAS-O or ATO can calculate a series of control target points (position, time and speed) as discrete information and send them to the train in real time by analyzing the running state of the train, instead of only sending mobile authorization or temporary speed limit commands. DAS-O or ATO makes speed recommendations or directly controls train operation according to control target points and gives feedback to the traffic management center. The key to computing the trajectory is to determine the main target point, which is composed of target position, target speed and target time. When the train travels to the target position at the target speed at the target time, the unplanned stop can be avoided. The main-target point can be determined by the estimated nonoptimized trajectory and the estimated conflict resolution time. As shown in Fig. 4.16, the red dotted line represents the trajectory of unoptimized train 2. 1. The train affected by the crossing conflict, travels with normal train speed v0. 2. Due to train conflict, the train did not receive a new movement authority, in order to prevent the train from running out of the end of the movement authority (EOA), the train brake in the position of Pbsp. 3. Standstill, until the train receives a new MA.

130

4. Influence of variable approach locking section rules

TABLE 4.4 Comparison of DSS, DAS-C, DAC-O, and ATO. Current system

DSS

DASC

DASO

ATO

Traffic management by re-ordering re-routing re-timing:

No

Yes

Yes

No

No

Traffic management by optimizing train speed:

No

No

Yes

No

No

Optimized onboard functionality:

No

No

No

Yes

Yes

Automatic speed control:

No

No

No

No

Yes

Progress:

Widely applied

1. Efficient traffic management 2. Conflict prevention

1. Improved train driving performance 2. Enhanced onboard functionality

Problem:

Low efficiency

1. Lack of advanced onboard functionality 2. The quality of transmitted train data 3. No guarantee that each conflict resolution can be executed accurately

1. Need additional onboard support for train’s overspeed protection 2. Need additional infrastructure support for traffic regulation 3. Not widely applied for dense and mixed-traffic mainline railway

System

Conflict

FIG. 4.14

Train conflict situation.

4.3 Integrated traffic management with station signal system

FIG. 4.15

131

Traffic management system using DSS, DAS-C, DAS-O and ATO.

Speed

Vtar

Current train speed v0

Target Train Speed

EoA

Conflict Detected time(Current time)tcur v0

ptar

Estimated Conflict resolution Time tconfResol

= pbsp

Position

ttar Time

FIG. 4.16

Train state comparison.

4. After a period of time tconfResol, train 1 left the conflict zone and the conflict was resolved. Train 2 received a new MA and restart to leave the conflict zone. The optimization objective of the operation process hopes that the train can avoid the unplanned stop caused by conflicts and run at the highest speed in the subsequent process, so the target speed vtar is the maximum speed the train can travel at before braking begins. Since the train obtains a new MA after tconfResol time, the main target time ttar is tconfResol. Based on ttar and vtar, the main target position is Pbsp. If the train arrives at Pbsp in advance, the train will apply brake and stop because it has not obtained the new MA. If the train arrives at Pbsp late, the driving efficiency will be reduced. The formula for the main target point is shown in Eq. (4.18), and the meaning of each symbol is listed in Table 4.5.

132

4. Influence of variable approach locking section rules

TABLE 4.5 Notation of the symbol. Main - targetcc

Main target point of the conflict

Ptar

Main target position

Pbsp

Braking start point

PEOA

Position of End of Authority

ΔSnonOpBr

Braking distance in the nonoptimized trajectory between Pbsp and PEOA

vtar

Main target speed

max{v(Pbsp)}

Maximum permitted train speed at Pbsp

ttar

Main target time

tconfResol

Estimated conflict resolution time

8 PEOA  ΔSnonOpBr > < Ptar ¼ Pbsp ¼    Main  targetcc ¼ vtar ¼ max v Pbsp > : ttar ¼ tconfResol

(4.18)

Rail Control System (RCS) is a new generation dispatching system, which is the result of independent research and development supported by Swiss Railway OCC project. RCS system is divided into three modules, RCS-DISPO, RCS-HOT, and RCS-ADL, which has the functions of train operation state monitoring, conflict monitoring, timetable adjustment, train speed adjustment, etc. As shown in Figs. 4.17 and 4.18, the RCS-DISPO module automatically identifies the potential conflicts, and displays the conflict information on the man-machine interface to remind the dispatcher to conduct the corresponding adjustment operation. The RCS-HOT module adjusts the timetable, and the RCS-ADL module calculates the train speed curve according to the adjustment scheme and sends the speed curve to the train [20].

Train speed, position

Train

ILTIS

conflict predicted

rescheduling

RCS-DISPO

RDS-HOT

Speed control orders Speed control

FIG. 4.17

Workflow of RCS system.

RCS-ADL

4.3 Integrated traffic management with station signal system

133

According to statistics, after the RCS system was put into operation in 2016, the departure interval of local stations can be shortened to 2 min, and the delay time of trains can be reduced by about 2000 min every month.

4.3.2 High-density European railway traffic management The European Rail Traffic Management System (ERTMS) is a signaling and train control system promoted by the European Commission (EC) and International Union Railway (UIC) for use throughout Europe [22,24]. Its purpose is to establish a railway signal standard that can not only be compatible with the existing signal system, but also be promoted in all European countries, to ensure the compatibility of trains and wayside signal systems and improve transport efficiency. ERTMS can be divided into two parts: the first part is ETCS and the second part is GSM-R. Fig. 4.19 shows the system architecture of ERTMS/ETCS and its interface with GSM-R and signal subsystem. The increasing demand of railway traffic demand leads to the congestion of railway nodes, which becomes the bottleneck of railway infrastructure construction[25]. The High Density European Traffic Management System (HD-ERTMS) was developed to solve this problem. It is compatible with the Italian railway system and can be applied without changing the existing infrastructure [26]. The characteristics of HD-ERTMS is: 1. Optimized train speed curve with parameters sent from the ground equipment;

FIG. 4.18

Conflict detection.

134

STM

4. Influence of variable approach locking section rules

Train

Driver

Downloading Tool

Train Interface Unit

Driver Machine Interface

Juridical Recording Unit

European Vital Computer

Balise Transmission Module

Eurobalise

Onboard ERTMS/ETCS

Loop Transmission Module

Euroloop

National System

FIG. 4.19

Odometry

Euroradio

Euroradio Trackside Radio Infill ERTMS/ETCS Unit

Interlocking, Linside Electronic Unit

Euroradio

Control Center

RBC1 RBC2

GSM-R Mobile Unit

GSM-R Fixed Network

Key Management Center

The structure of ERTMS/ETCS and it interface with GSM-R and other signal

system.

2. Speed is managed by the Static Speed profile (SSP) rather than the signal; 3. Mixed traffic operation between ERTMS train (virtual subsection) and non-ERTMS train (real section); 4. Parameterization of Interlocking (IXL) and Radio Block Center (RBC); 5. Using virtual Block Sections in line and station; Using virtual Block Sections in line and station is the main characteristic of HD-ERTMS. In order to allow more than one train to enter the same block section, the original block section will be divided into two or more part by virtual joints [26,27]. The standard length of traditional block section is 900 or 1350 m and it is protected by signal. Because ERTMS/ETCS Level 2 does not add new signal, virtual joints is used in HD-ERTMS to divide the traditional block

135

4.3 Integrated traffic management with station signal system

section into several partial virtual block section. Fig. 4.20 illustrates the differences between HD-ERTMS and traditional ERTMS. In the HD-ERTMS area, as a Level 2 signaling, a radio blocking center called “Nodal RBC” is used, which will manage all HD-ERTMS trains. The occupation status of HD segments will not be determined only on the basis of information provided by interlocking or automatic block control devices, but will be managed by IXL (Interlocking). IXL can declare the HD section state (occupied, free and undefined) on the basis of link to Nodal RBC to check trains integrity, as shown in Fig. 4.21. Meanwhile, The dynamic transition between High Density zones and no HD-ERTMS zones is also important and should be defined in the operational plan to make it transparent to conventional signaling systems and to ensure mixed traffic (e.g., ETCS trains and SCMT trains); When ETCS Level 2 degraded, any trains specialized for High Density must be run in SCMT mode. To implement the HD-ERTMS system, station and junction interlockings should be computerized so that all the HD area can be controlled and commanded by Computer Based Interlocking (CBI). Meanwhile, all the ETCS components will be optimized: 1. ETCS (European Traffic Control System), operational protection, spacing and continuation system signals, will be optimized through the development of TSI (Interoperability Technical Specification); 2. GSM-R (Global System for Mobile Communications-Railway) for communication between ground and on-board systems; 3. TMS (Traffic Management System) is used to manage and supervise train traffic and dispatch high density trains.

Current situiation PBA101

PBA103

Train

101

Future situation with HD-ERTMS technology PBA101

PBA103

Train

101/1

FIG. 4.20

HD-ERTMS technology.

101/2

101/3

136

4. Influence of variable approach locking section rules

RBC New virtual subsection PBA101

PBA103

Legacy track circuit New cross IXL indicator Legacy lineside signal

FIG. 4.21

System functionalities architecture.

Fig. 4.22 shows the scene of two HD-ERTMS equipped trains tracking in a conventional block section. In scenario 1, ETCS Train 1 is approaching signal PBA101, whose function is to protect the block section 101. Interlocking logics had checked the clearness of section 101. RBC sends to ETCS Train 1 the MA (represented in green) and MA extends to at least the next signal PBA 103. In scenario 2, ETCS Train 2 is approaching the signal PBA101. When ETCS Train 1 occupies block partition 101, PBA101 will display a red light, i.e., a danger signal (block partition 101 is occupied). At the same time, RBC receives the position information of ETCS Train 1 and puts the first virtual segment 101/1 in the occupied state. In scenario 3, ETCS Train 1 has left virtual segment 101/1. According to the detection information of ETCS Train 1, RBC confirms that virtual segment 101/1 is cleared and RBC transmits to interlocking that information. After that, the interlocking establishes the lighting of “X” in PBA101 to allow the run of ETCS Train 2, whose MA is shown in blue in Fig. 4.22. Until ETCS Train 1 exits block section 101, PBA101 will display a red light (danger state) and ETCS Train 2 can pass through signal PBA101 without restriction. In scenario 4, RBC detects the position information and confirms that virtual section 101/3 is occupied by ETCS Train 1 and section 101/2 is occupied by ETCS Train 2. RBC which transmits that information to interlocking, the “X” is turned on so that the ETCS Train 3 can receive the MA (represented in orange) to advance in section 101/1.

4.3.3 Parallel control system for high-speed railway Parallel control of high-speed railway refers to the construction of virtual artificial high-speed railway system by using big data, artificial intelligence, cloud computing, and advanced sensing technology. The artificial high-speed railway system and the actual high-speed railway system parallel execution. Through the interaction of them complete the

137

4.3 Integrated traffic management with station signal system

SCENARIO 1 PBA101

PBA103

101

ETCS Train 1

101/1

101/2

101/3

SCENARIO 2 PBA101

PBA103 ETCS Train 1

101/1

101 101/2

101/3

SCENARIO 3 PBA101

101

ETCS Train 1

PBA103

ETCS Train 1

101/1

101/2

101/3

SCENARIO 2

101

PBA101

101/1 FIG. 4.22

PBA103 ETCS Train 1

ETCS Train 2

ETCS Train 3

101/2

101/3

Tracking scenario of two ETCS trains.

management and control of the actual system, the experiment and evaluation of the relevant behavior, the related personnel and system learning and training. Analyze the results of the implementation of the two to predict the future situation, adjust their management and control methods, to achieve the implementation of effective solutions, learning and training. Literature [27] uses parallel control method to construct dynamic scheduling and traffic management system. Intelligent scheduling method using parallel control can generate more stable train schedule and more accurate control. Fig. 4.23 shows the basic framework of parallel control system [28,29]. Using big data technology, virtual object, virtual system, virtual process, and virtual human factor parallel to object process, system, and human factor is constructed and designed [30]. A large number of artificial

138

4. Influence of variable approach locking section rules

Actual system

Artifical system Management & control

Management & control Observation & evaluation

Management & control

FIG. 4.23

Control & observation

Experiment & evaluation

Observation & evaluation

Learning & training

The framework of parallel control.

data are generated by computational experiments on virtual platforms, which are then used for reinforcement learning to enhance the intelligence and decision-making capabilities of the system. Meanwhile, the decisions are evaluated according to various operating scenarios. Finally, physical object, processes, and systems interact with virtual object, virtual processes, and software systems, forming closed-loop feedback decisionmaking processes to control and manage complex systems. This is the core concept of the ACP-based parallel intelligent systems, as shown in Fig. 4.24. In ACP, “A” represents “artificial system,” which is the generalized form of software-defined system. “C” represents “computing experiment,” which aims to analyze and evaluate the system performance through experiments in virtual platform; “P” represents parallel execution, whose goal is to get innovative and normative decisions [31,32]. As shown in Fig. 4.24, parallel control can be divided into three modes: learning and training, experimental evaluation and control management. Therefore, the basic principles of the high-speed railway parallel control system are given as follows:

Cyberspace

with softwaredefined users and devices

Artifical System

Management & control

FIG. 4.24

Social Space

Physical Space

Artifical System with actual users and physical devices

Experiment & evaluation

Learning & training

Parallel execution for control and management for complex systems.

139

4.3 Integrated traffic management with station signal system

(1) Based on the multiagent framework, an artificial system equivalent to the actual system is established to understand the evolution mode of various factors in the system. (2) Performing a calculation experiments or tests on the artificial system to simulate specific train operation and movement, as well as dispatch and management, and evaluate and adjust the entire system in a comprehensive, accurate and timely manner. (3) Combining the above-mentioned learning and understanding experience, the artificial railway system is combined with the actual system for parallel execution. Fig. 4.25 is the basic framework of parallel high-speed railway system that constructed by agent method, including equipment agent, personnel agent, operating environment, various rule bases, etc. In computational

Microscopic

Actual HRS system

Open Source Data

Artifical HRS system

Mesoscopic

Control

Development Plan

Management

Traffic Control

Coordination and Optimization

Adaptive Dynamic Programming

Quality of service

Parallel Execution Layer

C

Experimental Calculation Layer

Experimental Design

Experimental Implementation

Experimental Analysis

A

Data Knowledge Layer

Scene Library

Configuration Library

Algorithm Library

Database

Model Library

Knowledge Base

FIG. 4.25

Agent-Based Control

Emergency Management

P

Fundamental Building Layer

Parallel Comuting

Macroscopic

Linguistic Dynamic Systems

Physical Structure

Standards

Software Interface

Configuration Tool

Hardware Interface

Other Components

The basic framework of parallel HRS.

140

4. Influence of variable approach locking section rules

experimental layer, experiments are designed according to the rules in the rule base to simulate the events that have occurred and deduce and predict the possible behaviors and states of the system [28,33]. The proposed artificial HRS mainly consists of four parts, namely, equipment agents, personnel agents, an operating environment, and a rule base. The basic structure is shown in Fig. 4.26. Equipment agent includes train unit, control unit, trackside equipment units and organization units. In the working process of the actual HRS control and management, every person who contributes to the systems will be considered as a personal agent. Operating environment refers to the actual physical environment, which consists of infrastructure, communication system, power grid system, and natural environment [34]. The rule basis is the driving rules to be followed by railway operation, including equipment operation manual, driving management regulations, personnel management regulations, train control system work records and relevant industry standards, etc.

Equipment Agents

Personal Agent

Train Unit

Control Unit

Organization Unit

Trackside Equipment Units

Passenger

Trackside Operation

Regulatory Agencies

Control Unit

Agency Personal

Operating Environment

Natural Environment

Line Information

Along Building

Power Supply System

Communication System

Command File

Work Book

Agency Equipment

Train Control System

Rule Base

FIG. 4.26

Artificial HRS model.

4.3 Integrated traffic management with station signal system

141

The artificial HRS will be used as a platform for computational experiments. Through various experiments on the platform, many tests that cannot be performed on the actual system can be carried out according to the units and personnel involved. The results are analyzed to find out the problems in the operation process make further adjustments, which provides a low-cost high efficiency way for feasibility verification and evaluation for design and planning. There are four computational experimental plans on train operation, central traffic control, services, and emergency dispatching: Train operation [35]: 1. Train operation control. Operation monitoring and control, overspeed protection, TSR, emergency braking (EB), and train location. 2. Safety monitoring. Automatic data collection, measurement and detection of real-time monitoring and control of various tracks and lines, signaling systems, communication systems, and offtrack hazards, achieving alarm and early warning, information feedback analysis, and online tracking. 3. Organization and planning. Train scheduling, adjustment of train schedule charts, number checking of arrival and departure trains, and automatic generation of traffic timetables. Traffic management: 1. According to the administrative architecture, the whole traffic management system is divided into three levels: the dispatching system of the Ministry of Railways, the dispatching and directing center of the Railway Bureau, and the dispatching offices in various stations. 2. According to the nature of the job, the dispatching system is divided into vehicle depots, communication and signal depots, locomotive terminal, and maintenance base. Services: The content of railway service is passenger service, freight service, and railway staff management service, among which passenger service has the highest priority, including on-board service scheduling consultation and conflict resolution, etc. Emergency dispatching: 1. The correction of human errors; 2. The handling of natural disasters; 3. The handling of un avoidable problems such as device failure and track aging;

142

4. Influence of variable approach locking section rules

The computational experiment platform is the most important part of the computational experiment, which is used to evaluate the influence of controllable and uncontrollable direct and indirect factors on the system output, as shown in Fig. 4.27. In the process of calculation experiment, the HRS system, as a repeatable simulation platform, stores the data generated by the scheme database calculation experiment, which will be classified and archived to provide scheme calculation data and debugging experience for future experiments and parallel execution. Actual HRS is difficult to measure, predict and analyze, and it is impossible to perform experiments in the actual system, by repeating a large number of computational experiments on the artificial railway system platform and using enough schemes and possible solutions, the artificial platform and the actual railway system can be combined to perform the actual control and management in parallel. The parallel execution of the actual high-speed railway system and the manual high-speed railway system is the process of problem raising, problem analysis and calculation experiment and analysis. Through real-time monitoring of the actual system to master the state changes of the actual system and adjust the optimal scheme running on the artificial system in real time to achieve the purpose of formulating the control and management scheme corresponding to the current running state of the actual system in time. Effectively improve the security and efficiency of actual system operation, as shown in Fig. 4.28. There are two types of parallel execution. 1. Global execution. All modules of the artificial high-speed railway system and the actual system are involved in the parallel execution process. Using different schemes to obtain corresponding results, which will be analyzed and used to make appropriate modifications to protocols make appropriate modifications to the scheme by analyzing Generation Mechanism Controllable Factors Uncontrollable Factors Direct Factors Indirect Factors

Personal Behavior

Spread Mechanism Conversion Mechanism

grow

Equipment Response

Virtual Scenes in Artificial HRS

Environment Effect

Coupling Mechanism

FIG. 4.27

Data Collection

Integration

breed Rule Restriction Derivation Mechanism

Results Output

Scene1

Computational experimental platform.

Scene3 Data Record

Scene2 Scene4

Visualization

143

References

Train Operation Scheme

Holidays

Bad Weather

Events

FIG. 4.28

High-speed Railway Artificial System

Calculation Experiment

Evaluation of Artificial Systems

Dynamic Monitoring Structural adjustment mechanism

Comparison of Evaluation

Disaster early-warning mechanism

Calculation Experiment Actual Highspeed Railway System

Dynamic Monitoring

Evaluation of Actual Systems

Parallel execution.

the implementation process and results. Advanced execution of the artificial system platform can predict the evolution and behavior of the actual system. 2. Local Execution. Partial execution According to the needs of the research plan, select some units for parallel execution, analyze and evaluate the results obtained, and adjust and optimize accordingly.

References [1] GB/T 50262-2013, Standard for Basic Terminology of Railway Engineering. [2] S.S. Fu, Approach sections should have sufficient length – signal specification to resolve doubts (one), Railw. Commun. Signal Des. (1) (2001) 1–4. 37. [3] H. Wei, Discussion on the length design of high-speed railway train approach lock section, Railw. Commun. Signal Eng. Technol. 11 (1) (2014) 20–22. 28. [4] Z. Liang, G. Xiuqing, A calculation method of dynamic approach locking section based on CBTC, Railw. Commun. Signal 49 (12) (2013) 34–35. 37. [5] J. Wang, Y. Yu, R. Kang, J. Wang, Z.-C. Li, A novel space-time-speed method for increasing the passing capacity with safety guaranteed of Railway Station, J. Adv. Transp. 2017 (2017), 6381718. [6] C. Feng, Y. Zhiming, Y. Lu, et al., Reliability and safety evaluation of intelligent CTC autonomous machine system for high-speed railway, Acta Automat. Sin. 46 (3) (2020) 463–470. [7] M. Abril, F. Barber, L. Ingolotti, et al., An assessment of railway capacity, Transp. Res. E: Log. Transp. Rev. 44 (5) (2008) 774–806. [8] A. Dicembre, S. Ricci, Railway traffic on high density urban corridors: capacity, signalling and timetable, J. Rail Transp. Plann. Manag. 1 (2011) 59–68.

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[9] X. Zhang, L. Nie, Integrating capacity analysis with high-speed railway timetabling: a minimum cycle time calculation model with flexible overtaking constraints and intelligent enumeration, Transp. Res. C: Emerg. Technol. 68 (July) (2016) 509–531. [10] J. Armstrong, J. Preston, Capacity utilisation and performance at railway stations, J. Rail Transp. Plann. Manag. 7 (2017) 187–205. [11] L. Min, H. Baoming, L. Dewei, High speed railway stations through capacity calculation and evaluation, J. China Railw. Soc. 34 (004) (2012) 9–15. [12] G. Bin, Z. Leishan, T. Jinjin, et al., Research on robust chain optimization of operation plan of high-speed Railway Station, J. China Railw. Soc. 39 (7) (2017) 10–17. [13] L. Pei, Capacity Calculation and Enhancement of High-Speed Railway Based on Precise Study of Station Interval Time, Beijing Jiaotong University, 2019. [14] S. Zhao, S. Wei, C. Bogen, et al., Optimization of high-speed train tracking based on moving block space-time occupancy band model, J. China Railw. Soc. 43 (5) (2021) 87–96. [15] T. Changhai, Z. Shoushuai, Z. Yuesong, et al., Study on train tracking interval time of high speed railway, J. China Railw. Soc. 37 (10) (2015) 1–6. [16] D. Hasegawa, G.L. Nicholson, C. Roberts, et al., The impact of different maximum speeds on journey times, energy use, headway times and the number of trains required for phase one of Britain’s high speed two line, in: COMPRAIL 2014, 2014. [17] Z. Zixuan, Simulation and Analysis of Time Compression Strategy for High-Speed Railway Train Tracking Interval, Southwest Jiaotong University, 2019. [18] G. Caimi, A model predictive control approach for discrete-time rescheduling in complex central railway station areas, Comput. Oper. Res. 39 (11) (2012) 2578–2593. [19] T. Tang, L. Kaicheng, S. Su, J. Yin, Analysis of characteristics of Swiss railway dispatch command system and its enlightenment to China, China Railw. (11) (2019) 18–23. [20] J. Yin, W. Zhao, Fault diagnosis network design for vehicle on-board equipments of high-speed railway: a deep learning approach, Eng. Appl. Artif. Intell. 56 (November) (2016) 250–259. [21] X. Rao, M. Montigel, U. Weidmann, A new rail optimisation model by integration of traffic management and train automation, Transp. Res. C 71 (2016) 382–405. [22] W. Jian, Z. Fulong, B. Cai, et al., A review of ERTMS-regional development, J. China Railw. Soc. 34 (01) (2012) 60–64. [23] X. Rao, M. Montigel, U. Weidmann, Potential railway benefits according to enhanced cooperation between traffic management and automatic train operation, IEEE, 2013, pp. 111–116, https://doi.org/10.1109/ICIRT.2013.6696278. [24] S. Abed, European rail traffic management system – an overview, Iraqi J. Electr. Electron. Eng. 6 (2) (2010) 172–179. [25] I. Colla, A. Consilvio, A. Olmi, et al., High density – HD using ERTMS: the Italian solution for the railway traffic management, IEEE, 2018. [26] F. Cuppi, V. Vignali, C. Lantieri, et al., High density European rail traffic management system (HD-ERTMS) for urban railway nodes: the case study of Rome, J. Rail Transp. Plann. Manag. 17 (2021), 100232. [27] H. Dong, H. Zhu, Y. Li, et al., Parallel intelligent systems for integrated high-speed railway operation control and dynamic scheduling, IEEE Trans. Cybern. 48 (2018) 3381–3389. [28] F.-Y. Wang, Parallel systems approach and management and control of complex systems, J. Control Decis. (5) (2004) 485–489. 514. [29] B. Ning, H.R. Dong, W. Ding, et al., ACP-based control and management of urban rail transportation systems, IEEE Intell. Syst. 26 (2) (2011) 84–88. [30] B. Ning, F.-Y. Wang, H.R. Dong, et al., Research framework of parallel control and management system for high-speed railway. Complex systems and complexity, Science 7 (4) (2010) 11–21.

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C H A P T E R

5 Optimize control method of train control system to shorten tracking interval The train tracking interval is the main factor affecting the carrying capacity of high-speed railway. Compressing the train tracking interval can significantly improve the line’s carrying capacity, so as to relieve the strain of the carrying capacity of the busy trunk line. This chapter introduces a series of methods to shorten the train tracking interval in the fixed block and moving block systems from the perspective of optimizing system control methods and system engineering design, such as track circuit adaptive dynamic coding, train deceleration in advance, train synchronization control, etc. These methods can effectively shorten the train tracking interval and improve the carrying capacity with little or no additional equipment.

5.1 Adaptive dynamic coding for the track circuit in the CTCS-3 In China, the lines where the speed is below 160 km/h adopt a fourdisplay automatic block, and the lines whose speed is above 200 km/h adopt an eight-display automatic block. The four-display modes represent “red light,” “yellow light,” “green and yellow light,” and “green light.” The eight display mode adds “Green 2,” “Green 3,” “Green 4,” and “Green 5.” Although the added information will not be recognized by the driver, the train’s control system can recognize it [1]. The Chinese Train Control System Level 3 (CTCS-3) has been adopted for the 350 km/h high-speed line. However, due to the train’s increased speed, the eight display’s additional information is still insufficient to indicate the space distance between trains. To address this, the length of the block section is extended in the CTCS-3 system, and a two-segments

Theory and Technology for Improving High-Speed Railway Transportation Capacity https://doi.org/10.1016/B978-0-323-99700-3.00011-6

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Copyright © 2023 Elsevier Inc. All rights reserved.

148

5. Optimize control method of train control system

track circuit and an individual three-segments track circuit form a block section [2]. This design reduces the resolution of the block section and also reduces carrying capacity. The CTCS-3 track circuit adaptive dynamic coding method dynamically combines the block sections according to the different positions of the two track circuits in the same block section, dynamically adjusts the information encoding of the track circuit, shortens the tracking interval of the train, and improves the carrying capacity.

5.1.1 The existing track circuit coding principle for the CTCS-3 The track circuit is the basis for train positioning and tracking, as well as the technical basis for interlocking and blocking. The CTCS-3 train control system integrates all the equipment and functions of the CTCS-2 train control system. CTCS-2 is the backup system of the CTCS-3. In the CTCS-3 train control system, the ZPW-2000A noninsulated analog track circuit is used to continuously provide the number of unoccupied blocks in front of the train to realize the track circuit occupancy detection and automatic block. Different from the existing general speed lines, there is no block signal in the section of CTCS-3 high-speed railway, and signal signs are only set at the demarcation point of block section. 5.1.1.1 ZPW-2000A track circuit structure and code sequence The ZPW-2000A track circuit adopts electrical insulation without mechanical insulation joints. It consists of a sender, receiver, lightning protection analog cable network box, and track relay (GJ) that are installed indoors and a tuning unit, air-core coil, matching transformer, and several compensation capacitors that are installed outdoors. The structure of the ZPW-2000A track circuit is illustrated in Fig. 5.1. In practical applications, the two track circuits in the same block section have their own transmitting equipment and receiving equipment. When realizing train occupancy detection and transmitting track circuit code information, the two track circuits are independent of each other and do not affect each other. The ZPW-2000A track circuit contains 18 lowfrequency information codes, and different information codes represent different states of the front block section, as shown in Table 5.1. The track circuit coding sequence of CTCS-3 train control system is shown in Fig. 5.2. Wherein, B0 to B7 are block sections, B0 is composed of track circuit TC0 and TC1, B1 is composed of track circuit TC2 and TC3, and so on. There are two track circuits in the same block section, when the track circuit where the front-running train is located is shortcircuited by the train wheels, B8 is in the occupied state. When the transmitter of the B7 track circuit TC15 receives that TC16 is in the occupied state or the track circuit information code is JC code, it

149

5.1 Adaptive dynamic coding for the track circuit in the CTCS-3

Matching Transformer

100m

Tuning Unit

Air-Core Coil

Compensang Capacitance

Tuning Area

Tuning Unit

Main Track Circuit

Tuning Unit

Tuning Unit

Air-Core Coil

Tuning Area

Matching Transformer

Outdoor Cable Simulave Network

Total Length 7.5km

Cable ZC03

Cable ZC03

Indoor

FIG. 5.1

Receiving

Cable Simulave Network

GJ

Sending

Structure for the track circuit.

sends the HU code to the track circuit. Because B7 is in the unoccupied state, the information code of TC14 remains consistent with TC15. When the transmitter of the B6 track circuit TC13 receives the HU code of TC14 and sends the U code to the track circuit, TC12 keeps the same with TC13. Similarly, the two-segment track circuit of B5 sends LU codes, and so on. The red line in Fig. 5.2 is the speed monitoring curve of the on-board equipment that controls the operation of the train, which ensures the safety of the train’s tracking operation in the section. The coding of automatic block track circuits can be divided into relay coding and electronic coding. The relay coding is accomplished by using a large number of relay logic circuits, and the coding circuit distinguishes different low-frequency codes by the state of the relay contacts of the front block section. The electronic coding is to directly code the track circuit while collecting the train route, the track circuit information code, and the GJ state by computer. In China, relay coding has been adopted in general-speed railways and electronic coding in high-speed railways. The independence of track sections and the electronic coding method provide technical support for adaptive dynamic coding of track circuits. 5.1.1.2 The existing CTCS-3 track circuit coding principle and shortcoming The Train Control Center (TCC) collects train route and GJ status information from the computer interlocking equipment through the signal safety data network. According to the train route information and track section status, the TCC achieves the encoding function of the track circuit

TABLE 5.1 The low-frequency information allocation. Number

1

2

3

4

5

6

7

8

9

Information name

L5

L4

L3

L2

L

LU

LU2

U

U2S

Frequency (Hz)

21.3

23.5

10.3

12.5

11.4

13.6

15.8

16.9

20.2

Number

10

11

12

13

14

15

16

17

18

Information name

U2

UUS

UU

HB

HU

H

Frequency switching

JC (detection)

L6 (reserved)

Frequency (Hz)

14.7

19.1

18

24.6

26.8

29

25.7

27.9

22.4

(1) L6(reserved): Indicates that eight or more blocked sections in front of the train are unoccupied. (2) L5: Indicates that seven or more block sections in front of the train are unoccupied. (3) L4: Indicates that six block sections in front of the train are unoccupied. (4) L3: Indicates that five block sections in front of the train are unoccupied. (5) L2: Indicates that four block sections in front of the train are unoccupied. (6) L: Indicates that three block sections in front of the train are unoccupied. (7) LU: Indicates that two block sections in front of the train are unoccupied. (8) LU2: Indicates that two block sections in front of the train are unoccupied. Special code added to speed up the Beijing-Tianjin Intercity. (9) U: Indicates that one block section in front of the train is unoccupied. (10) U2S: Train speed limit operation, predicts that the block section ahead of the train is UUS. (11) U2: Train speed limit operation, predicts that the block section ahead of the train is UU. (12) UUS: Train speed limit operation (default speed limit: 80 km/h), indicates that the ground signal of the train approaching is open to the siding position of Turnout 18 and above, and the next signal is open to the straight direction of the turnout or the siding position of Turnout 18 and above. Or it means that the train approaches the ground signal with the branch switch line and opens to the siding position of Turnout 18 and above. (13) UU: Train speed limit operation (default speed limit: 45 km/h), indicates that the ground signal of the train approaching opens the route through the siding position of the turnout. (14) HB: Indicates that the train approaching the home signal or route signal opens the call-on signal or through signal displays the permissive signal. (15) HU: Indicates the need to take parking measures in a timely manner. (16) H:Indicates the need to take emergency parking measures immediately. (17) Frequency switching: Upside and downside carrier frequency switching, used to select and lock the carrier frequency received by the cab signal. (18) JC (detection): Used for section reverse operation and the station closed loop detection, not as cab signal.

151

5.1 Adaptive dynamic coding for the track circuit in the CTCS-3

Preceding Train

Track Circuit TCS Information Blocking

FIG. 5.2

TC 0

TC 1 L5 B0

TC 2

TC 3 L4 B1

TC 4

TC 5 L3 B2

TC 6

TC 7 L2 B3

TC 8

TC 9 L B4

TC 10

TC 11 LU B5

TC 12

TC 13 U B6

TC 14 TC 15 HU B7

TC 16

TC 17 8

The CTCS-3 automatic block and track circuit code sequence.

carrier frequency and low-frequency information in the station and section and controls the transmission direction of the track circuit. The line boundary information data is transmitted between the adjacent TCCs and includes boundary block section status, boundary block section coding, and so on. By obtaining the boundary sections state of the adjacent station and the information required for encoding, the continuity of the coding for two sets of TCC control boundary track circuits is realized. The TCC track circuit coding principle for stations and sections is as follows: (1) Track circuit coding in the station ① When the train route signal is not open, the TCC should send the HU or JC code (low-frequency value is 27.9 Hz, namely, the detecting code) to the track and send the JC code to the switch section. ② After the receiving route is open, the TCC controls the relevant track sections of the receiving route to code according to the status of the starting signal, and the station track sections are identical with the receiving route sections. ③ After the train departure signal is opened, the departure track is coded according to the state of starting signal and the first departure section, and the code of departure route section is identical with the first departure section. ④ When opening the receiving signal through the siding position of Turnout 12 and below, the TCC sends UU codes to the approaching section of the station, and the receiving route track sections are coded according to the starting signal state. ⑤ When opening the departure signal through the siding position of Turnout 12 and below, the TCC should send the UU code to the track, and the departure route section code is identical with the first departure section. ⑥ Coding is in accordance with relevant regulations for special circumstances, such as call-on receiving, nonwiring stations, route signal approaching section, and so on.

152

5. Optimize control method of train control system

(2) Track circuit coding in the section ① The track circuit shall be coded in the Tracking Code Sequence (TCS) when the train runs in the forward and backward direction in a section. ② The TCC obtains the boundary section state of adjacent stations and the information needed for encoding through security information transmission between stations, which actualizes the block section coding logic continuity. ③ As the boundary track circuit low-frequency code of the transmitted by the TCC at the adjacent station is the JC code, the boundary of the station should send the HU code. ④ For the track circuit in the section, the TCC shall send the code according to the track circuit TCS, the occupation state of the front track section, and the signal of the front station receiving signal. ⑤ When the block section is unoccupied, the low-frequency code of all track circuit segments in the same block section shall be consistent, as illustrated in Fig. 5.3. ⑥ For the block sections consisting of multiple track segments, the section where the train is located and all the sections in front of the train are coded normally, and the JC codes are sent to the rear sections, as illustrated in Fig. 5.4. ⑦ The TCC should control the track circuit equipment to send JC codes during the section change direction. After successful direction change confirmation, the TCC should code according to the new direction of operation. The changing direction process starting time is from the time when the TCC drives the direction relay, and the ending is the time when the TCC detects that the direction relay action is in place. In the CTCS-3 automatic block system, the target for tracking trains is the beginning end of the block section occupied by the preceding train, and the target point is relatively fixed. Whether the preceding train is located in the latter or the former part of the track circuit in the block

HU

L4

L3

L2

L

LU

U

HU

L5

FIG. 5.3 The tracking train occupied the latter track circuit of the block section.

HU

JC

L4

L3

L2

L

LU

U

HU

L5

FIG. 5.4 The tracking train occupied the former track circuit of the block section.

5.1 Adaptive dynamic coding for the track circuit in the CTCS-3

153

section, the tracking target points and tracking intervals identified by the tracking train are the same. When the preceding train is about to leave the block section occupied by itself, the tracking interval distance of the tracking train identification remains unchanged. In fact, the tracking interval error of the tracking train identification is a block section, which is 2000 to 2400 m. This error increases the tracking distance between trains and reduces carrying capacity.

5.1.2 Adaptive dynamic coding rules and algorithms for the track circuit 5.1.2.1 Principle of CTCS-3 track circuit adaptive dynamic coding Using track circuit adaptive coding, the TCC automatically adjusts the track circuit code according to the running position change of the train and the principle of tracking interval minimization. This is suitable only for track circuit coding during the train tracking operation in section. The adaptive coding of the track circuit is divided into two steps. First, the adaptive block section changes, the track circuit code changes automatically with the train running position, and the transformation process follows the interval TCS. Second, the block section will be reorganized and the track circuit will be coded according to the new block section. The TCC recombines the blocked sections according to the principle of minimizing the tracking interval and performs tracking coding according to the newly combined block section. As illustrated in Fig. 5.5a, AC, CE, EG, GI, and IK are the original block sections; The target point of the train tracking is the beginning of the block section where the preceding train is located, as shown in Fig. 5.5b; After using adaptive track circuit coding, BD, DF, FH, and HJ are the recombined block sections. The maximum error is a track circuit, which is about 1000 to 1200 m, as shown in Fig. 5.5c. The adaptive track circuit coding modifies some of the original coding rules. 5.1.1.2-(2)-③ is modified as follows: When the boundary track circuit under adjacent TCC jurisdiction is occupied, the station should send HU codes. If the boundary track circuit is unoccupied and the front track circuit is occupied, the boundary track circuit of the station should send HU codes and adjust the combination of the block section. The next track circuit should be coded according to the TCS starting from the U code. 5.1.1.2-(2)-⑥ is modified as follows: For the block section composed of multiple track segments, all the sections where the train is located and in front of the train operation are normally coded, and the HU codes are sent by the rear sections, and the block sections are recombined. At the jurisdictional junction, the rear sections are all sent HU codes by the TCC of the neighboring station.

154

5. Optimize control method of train control system

A

B

C

L

D

E

F

G

U

LU

H

I

J

K

I

J

K

JC

L5

L5

HU

a

A

B

C

L

D

E

F

G

U

LU

H

HU

b

A

B

L2

C

L

D

E

F

G

U

LU

H

I

HU

J

K

L5

c FIG. 5.5 A comparison of existing track circuit coding and adaptive coding.

5.1.2.2 CTCS-3 track circuit adaptive coding algorithms The block section and track circuit coding within the TCC jurisdiction are diagrammed in Fig. 5.6, and the sequence numbers increase sequentially along the coding direction. The flow chart of the adaptive coding algorithm forward for the track circuit is presented in Fig. 5.7. Block section recombination flag (BSR) ¼ 1 means to adjust the block section combination, BSR ¼ 0 means to keep the

FIG. 5.6 The TCC control range and code direction.

Start

Handling Code Direction BSR = 0 TCC(i,j+1,1)=HU TCC(i,j+1,2)=HU BSR = 1 TCC(i,j,2)=HU TCC(i,j+1,1)=HU

j =1

TCO(i,j,2)=1

Y

TCO(i,j,1) U TCO(i,j,2)=1 N

BSR = 0 Y TCC(i,1,1)=HU TCC(i,1,2)=HU

i-1 TCO(i-1,jmax ,2)=1

N Y

N

N

j =jmax Y Y

TCO(i,j,2)=1

BSR = 1 TCC(i,j,2)=HU

i-1

TCO(i-1,jmax,1)=1

Y TCO(i,j,2)=1 Y

N TCO(i,j,1)=1

1< j T? Y

Exit

N

N=1

The final speed of the train after decelerating in advance

Y Ia after decelerating in advance

N

vt > vmin?

Is after decelerating in advance

Min(Is, Id) >= Iaa?

Id after decelerating in advance

Y

N N Ia >= T?

Y N+1

FIG. 5.16

Flow chart of advance deceleration algorithm.

Terminate. output N, Iaa.

170

5. Optimize control method of train control system

5.2.2.2 Optimization of train tracking interval By decelerating the train in advance and equalizing the train arrival tracking interval and section tracking interval, the tracking interval of the train can be effectively reduced to improve the line carrying capacity. As the maximum value of the four tracking intervals, the train tracking interval is not only mainly affected by Ia, but also closely related to the size of Is, Id and Ip. Reducing the values of Is, Id and Ip and compressing the tracking interval of each stage of the train as a whole can play a positive role in improving the carrying capacity of the line. The section tracking interval of train is mainly affected by train running speed, braking distance, block section length and other factors. CTCS-2/ CTCS-3 Train Control system adopts automatic block, and the tracking target point of the following train is the beginning of the block section occupied by the previous train, and the train tracks the operation by one-time braking through the target distance. The common measures to shorten the section tracking interval of train include: adopting moving block with shorter tracking interval; Reduce the tracking distance of the train through the braking mode of “hitting the soft wall”; Use advanced control technology (such as virtual coupling), etc. In addition to the previously described methods, the reduction of train arrival tracking interval can also be carried out by optimizing CTC system and station track application scheme [12]. Compared with the one-time route unlocking mode, the optimized CTC system adopts the section unlocking mode. In the case of section unlocking, after the forward train clears the corresponding ground equipment, the route section can be unlocked. When the current train passes the last switch (LS) that overlapped the receiving route of the following train, the optimized CTC system can set the receiving route of the following train when the previous train has not reached the station track. Therefore, the running time of the original previous train from FS to the station track overlaps with the time of handling receiving route for the subsequent train, so that the train arrival tracking interval can be reduced by shortening the traveling distance of the subsequent train at the station (the value of Lth in Eq. (5.4)). On the basis of optimizing the CTC system, the application scheme of optimizing the train track in the station is to reduce the number of switches shared by the previous train and the subsequent train, further shorten the distance of the subsequent train in the station, and reduce the train arrival tracking interval. The departure tracking interval of train is mainly affected by train operation speed (the speed limit of station turnout), the length of the first departure section, the length and position of neutral zone [13]. The speed limit of turnout can be solved by using large turnout. However, large turnout will increase the length of station yard and cause an increase in

5.2 Train tracking interval optimization method

171

engineering cost [14], so it needs to be considered according to the actual situation in application. In order to ensure the effective operation of the power supply system of long and long trunk lines of high-speed railway, neutral zones shall be set between traction substations and substations. The neutral zone is an area without traction power. When the train passes through the neutral zone, it completely depends on inertia coasting. There are two schemes of highspeed railway neutral zone: 6 spans (short neutral zone) and 13 spans (long neutral zone). When the neutral zone is very close to the station, it will make it difficult for the train to increase the speed quickly after leaving the station, so as to increase the departure tracking interval of the train. At the same time, if the neutral zone is too long, it is likely that the train will fall into the neutral zone due to the improper setting form and position, which will aggravate the negative impact on carrying capacity. Therefore, “short neutral zone “ shall be adopted as far as possible for high-speed railway to reduce the impact on train tracking interval, and the setting position of neutral zone shall be far away from the throat area of the station as far as possible [13].

5.2.3 Train synchronization control Most of the methods to shorten the train tracking interval described above are only applicable to fixed block. For the problem of how to realize the train running at the minimum tracking interval under moving block, R. Takagi proposed a multi train synchronous control method. This method can not only control multiple trains to run at the minimum interval distance, but also enable multiple trains to brake at the same time, stop at the same platform of the station and depart from the same platform of the station at the same time. By minimizing arrival intervals and reducing travel time, train synchronous control can not only increase the carrying capacity of railways, but also contribute to the realization of complex railway services [15]. 5.2.3.1 Minimum train interval under moving block mode In the fixed block signal system, the railway section is divided into several block sections, and only one train can occupy one block section at any time. In this system, the movement authority (MA) of the tracking train is theoretically located at the beginning of the block section where the tail of the front train is located. MA will not move until the tail of the preceding train moves to the adjacent block section. In contrast, under the moving block signal system, the MA of the tracking train will be updated with the movement of the preceding train.

172

FIG. 5.17

5. Optimize control method of train control system

Schematic diagram of minimum interval of PMB.

According to different calculation methods of minimum train interval, moving block signal system can be divided into pure moving block (PMB) and relative moving block (RMB). Under the PMB mode, the train braking distance does not consider the speed, deceleration and other parameters of the preceding train, and is calculated with the target speed of 0 km/h, as shown in Fig. 5.17. In RMB mode, the train braking distance is affected by the speed, acceleration and other parameters of the preceding train, and the train tracking interval distance is smaller than PMB. In PMB mode, although the train tracking interval distance is not the minimum, the ample interval distance also ensures the safety of train operation. Assume that there are trains A and B, both running on a same piece of railway track in the same direction, and A is followed by B. Under the PMB, the minimum distance between the tail of train A and the head of train B, dmin(t), is given by the following equation d min ðtÞ ¼ dM + dBB ðxBN ðtÞ, vB ðtÞÞ

(5.7)

dM is the safety margin length, m; dBB(xBN(t), vB(t)) is the braking distance of train B, m. Generally, dBB depends on the speed of train B, vB(m/s), as the faster the speed the longer the braking distance. However, the position of train B (xBN) shall also be considered. If train B is on a down gradient section of a railway, the braking distance will be longer than what is expected on a level section. If such conditions are to be ignored, dBB will only depend on vB, then under the condition of constant deceleration βS(m/s2), the following relation is established: d min ðtÞ ¼ dM +

vB 2 2βS

(5.8)

5.2.3.2 Principle of train synchronization control method The train synchronization control method is suitable for multiple trains. Here, two trains are taken as examples to introduce the basic principle of the method. Assume that there are two trains A and B running in the same direction on the same railway track controlled by the PMB signaling system as described in Section 5.3.2.1, with B following A. Also assume that,

5.2 Train tracking interval optimization method

173

at time t ¼ 0, the distance between the tail position of train A, xAT(t), and the nose position of train B, xBN(t), is equal to the minimum distance dmin given by Eq. (5.7). When t > 0, control train B to keep the two trains in the state of xAT(t)–xBN(t) ¼ dmin(t), and the following formula can be obtained: xAT  xBN ¼ dM + dBB ðxBN + vB Þ

(5.9)

Differential about t on both sides of the equation dxAT dxBN d  ¼ vA  vB ¼ dBB ðxBN + vB Þ dt dt dt ∂dBB ∂dBB ¼ vB  β ∂xBN ∂vB B

(5.10)

where vA is the velocity of train A, m/s; βB is the deceleration of train B, m/s2; Note here that Eq. (5.9) holds when t > 0, and so must (5.10). If ∂dBB/∂vB ¼ 6 0, Eq. (5.9) can be re-written as βB ¼

ðð∂dBB =∂xBN Þ + 1ÞvB  vA ð∂dBB =∂vB Þ

(5.11)

This means that, if at t ¼ 0, xAT(0)xBN(0) ¼ dmin(0), where dmin (0) is given by Eq. (5.7), and if the deceleration of train B is continuously controlled to the value given by Eq. (5.11). when t 0, xAT(t)xBN(t) ¼ dmin(t), the train can run continuously at the minimum interval. Based on the above principles, it is assumed that the minimum interval between trains is calculated by Eq. (5.8). Assume that, when t  0, train A is at a standstill, that is both its velocity, vA, and its acceleration, aA, are zero. Therefore train B is also at a standstill when t  0. Also assume that, if t > 0, train A will accelerate at aA ¼ kβS, where βS is the maximum deceleration of train B, which is a constant value, and k is a constant and k > 0. Assuming that xAT(0) ¼ 0, the following equation holds 1 1 xAT ðtÞ ¼ aA t2 ¼ kβS t2 2 2 xBN ðtÞ ¼ xAT ðtÞ  dM 

vB 2 ð t Þ 2βS

1 vB 2 ð t Þ 1 vB 2 ð t Þ xBN ðtÞ ¼ aA t2  dM  ¼ kβS t2  dM  2 2βS 2 2βS

(5.12) (5.13) (5.14)

Differential about t on both sides of Eqs. (5.13), (5.14). aB(t) is the acceleration of train B at time t. when t 0, let aB(t) be a constant, that is, vB(t) ¼ aB(t)  t, the following equation is obtained
 aA β S t k  βS ¼ βS 1 + a B ðt Þ ¼ (5.15) vB t aB

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5. Optimize control method of train control system

vB ð t Þ ¼ a A t 

vB ðtÞaB ðtÞ vB ðtÞaB ðtÞ ¼ kβS t  βS βS

(5.16)

Substitute Eq. (5.15) into Eq. (5.16) to obtain the following formula qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi pffiffiffiffiffiffiffiffiffiffiffiffiffi βS + β2S + 4aA βS 1 + 1 + 4k (5.17) ¼ βS aB ¼ 2 2 This means that, if train A is to start at t ¼ 0 with constant acceleration of aA ¼ kβS, then train B can maintain the condition that the separation between trains A and B is the minimum distance as given in Eq. (5.8) by starting simultaneously with train A with constant acceleration of aB as given in Eq. (5.17). The discussion here can be applied to cases in which three or more trains exist and start simultaneously. If there is a train C behind train B on the same railway track, and after starting simultaneously, train C is also to maintain the condition that the separation between trains B and C is equal to the minimum distance as given in Eq. (5.8), the acceleration of train C, aC, is calculated as pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi pffiffiffiffiffiffiffiffiffiffiffiffiffi 1 + 1 + 2 1 + 4k (5.18) aC ¼ β S 2 The calculation principle of simultaneous braking of multiple trains is the same as above, which will not be introduced here. Readers can refer to Ref. [15] for derivation by themselves. 5.2.3.3 Application of train synchronization control method (1) Minimize train arrival interval Assume that the dwell time of train A is very long at a platform of the station, and train B, intending to arrive at the same platform of the station after train A has departed, approaches from behind train A and comes to a halt just outside the platform. In this case, it can be expected that, when train B comes to a halt, the distance between the tail of train A and the nose of train B is equal to dM as given in Eq. (5.7) or Eq. (5.8). After coming to a halt, train B can start simultaneously when train A starts, as shown in Fig. 5.18. The application of this method requires that train B comes to a standstill before it accelerates again to enter the platform, which will increase the energy consumption of trains because of increased number of starts and stops. Also, it may give passengers on train B additional inconvenience, such as “halt discomfort” caused by train stops. However, the fact that minimal departure-to-arrival headway can be realized by train B may mean that making an additional stop can have considerable positive impact on the operation of trains at bottleneck stations on an important railway line where increase in transport capacity is necessary.

5.2 Train tracking interval optimization method

175

FIG. 5.18 Distance-time graph of minimal departure-to-arrival headway at a platform of a station.

(2) Shorten the tracking interval of the train Express services on a main line railway are trains that link major stations with limited stops. Since these trains are attractive to passengers, the requests for some of the express services to operate through secondary lines branching from the main line may frequently arise so that passengers on these secondary lines can enjoy direct services to major stations without the need to change at junction stations where the secondary lines branch off. However, limitation of carrying capacity on the main line railway generally means that many of these requests cannot be met, especially if meeting the requests requires considerable increase in the number of express trains in part or all of the sections of the main line. However, limitation of transport capacity on the main line railway generally means that many of these requests cannot be met, especially if meeting the requests requires considerable increase in the number of express trains in part or all of the sections of the main line. Also, a train from the secondary line is coupled to a train on the main line to form a longer express train that runs into the major terminus. By applying the synchronization control as proposed in this paper, two or more express trains using shorter trainsets may be able to run much closer to each other on the main line, without the need to use too much of the carrying capacity or to couple or uncouple trains physically, as shown in Fig. 5.19.

176

5. Optimize control method of train control system

FIG. 5.19 Distance-time graph of two express trains running with synchronization control.

(3) Achieve more complex railway services Fig. 5.20 illustrates the “combined fast and slow services” scheduling scheme, which is widely accepted among suburban commuter rail operators across Japan. Under this scheme, stations are classified into major and minor stations, and express services will call at major stations only. In the example of Fig. 5.19, stations 0, 4 and 8 are the major stations served by express trains. All other stations are served by local trains only. In the case of Fig. 5.19, at least two platforms per direction are necessary at station 4 so that express and local services can be interconnected.

FIG. 5.20 Example train schedule based on the “combined fast and slow services” scheme.

5.3 Optimization method of block section design

FIG. 5.21

177

Example of a train schedule after replacing slow trains.

Although this scheduling scheme is widely adopted, it has been widely recognized that the “fast” services tend to attract too many passengers, resulting in poorer passenger experience such as congestion. If every local train in Fig. 5.20 is replaced by three shorter trains that utilize synchronization control proposed in this paper, the schedule may look like Fig. 5.21. Compared with Fig. 5.20, it is obviously much less convenient in the schedule of Fig. 5.21 for passengers traveling either from station Np (Np{1, 2, 5, 6}) to station Np + 1 or from station Nq (Nq{1，5}) to station Nq + 2. However, for most other passengers, Fig. 5.20 will mean faster travel compared to Fig. 5.21 because of reduced intermediate stops. More importantly, the difference of travel times of express and local services is smaller in Fig. 5.21 than in Fig. 5.20.

5.3 Optimization method of block section design In some cases, optimizing schedules to maximize line capacity is not sufficient to meet the requirements of minimum tracking intervals. At this time, the infrastructure layout and signal system need to be updated. Modifying the infrastructure layout can be very expensive, especially when dealing with underground lines, so upgrading or replacing the signal system is usually the first choice [16]. China’s high-speed railway adopts CTCS-2 or CTCS-3 train control system, and the section block mode is fixed block. The interval between trains is composed of several block zones. On-board ATP generates train braking curve according to target distance, target speed and train performance, and does not set the speed level of each block section. The block section provides the following trains with the tracking target point (the beginning of the block section occupied by the previous train) and the distance to the tracking target point (the sum of the lengths of each block section). The design of block section not only affects the train operation, but also

178

5. Optimize control method of train control system

determines the tracking interval between trains. It is one of the important factors affecting the section carrying capacity.

5.3.1 Influence factors of section signal point layout The carrying capacity improvement method based on block section optimization design is suitable for section signal engineering design under the condition of new line and existing line reconstruction. 5.3.1.1 Influencing factors of signal layout In the process of section signal layout, the signal display, train braking distance, limit length of track circuit and specific line conditions shall be considered [17], as follows: (1) Signal display: signal display is one of the key points of signal layout, which affects the number of block sections between trains. For example, the three-aspect automatic block needs to meet the requirements that the full braking distance of the train is less than the length of a block section; The design of block sections of CTCS-2/ CTCS-3 system shall meet the requirements that the sum of the lengths of each block section on the train tracking sequence is greater than the braking distance and additional time running distance of the train. (2) Train braking distance: in order to ensure the safety of train operation, the train must be able to stop in front of the danger aspect. Train braking distance affects the arrangement of the first and second approach signals and the test results of track circuit code sequence. At the same time, the braking distance will affect the train interval time, which is also the condition that needs to be checked in the signal layout process. (3) Limit length of track circuit: since the signal points must be arranged at the boundary of track circuit, the limit length of track circuit is also one of the factors to be considered in block design. The limit length of track circuit is different under different circuit conditions. In general, the limit length of roadbed track circuit is 1400 m and bridge is 1000 m. (4) Line conditions: according to the general design requirements of train control system [18,19], no through signal can be set on the wayside of CTCS-2 train control system. There is no through signal beside the rail of CTCS-3 train control system, and a signal sign board is set at the demarcation point of block section. Therefore, Bridges, tunnels and curvilinear areas with poor outlook conditions are no longer the limiting factors for signal layout. 5.3.1.2 Signal layout conditions (1) The home and departure signal, the reverse home and departure signal and other fixed signals are taken as the signal points of the fixed mileage, and the section signals are arranged after the location of the above signals is determined.

5.3 Optimization method of block section design

179

(2) Meet the requirements of the first and second approaching section length, which is calculated according to the station arrival interval. When the station arrival distance is long, the position of the second approach signal should be determined according to the station arrival interval to meet the requirement of tracking interval as far as possible. According to the position of the home signal and the preset second approach signal position, take the home signal plus a safe distance as the target stop point for reverse deduction of service braking. The speed at which the train reaches the second approach signal point is obtained according to the service braking speed distance curve, and then the arrival interval is calculated according to this speed and compared with the given interval time. When the arrival interval is less than and close to the given interval time, the position of the second approach signal point is obtained. The position range of the first approach signal is between the position of the second approach signal and the home signal, and is determined according to the track circuit length, track circuit code sequence and other conditions. (3) Meet the requirements for the position of the first departure signal from the station, that is, the distance from the reverse home signal to the first departure signal needs to meet the requirements for the operating distance within the equipment action and driver’s reaction time, the common braking distance and safety protection distance of various EMUs from the departure speed limit braking to stop, and meet the requirements for train departure interval at the same time. (4) Meet the requirements for code sequence display of track circuit of train control system. The code sequence of track circuit of train control system is HU, U, LU, L, L2, L3, L4 and L5. In order to ensure the code sequence display of the track circuit of the train control system, it must meet that when the train runs at the specified speed, the sum of the length of each block section on the train tracking sequence is greater than the sum of the train service braking distance, additional time (various equipment action time and driver reaction time), travel distance and safety protection distance. (5) Meet the requirements for the location of contact network tower, and the signal points in subgrade and bridge sections shall be arranged on adjacent contact network tower. Contact network tower is the most basic and widely used support equipment in catenary, which is used to bear the load of contact suspension and support equipment. If there is no contact network tower near the signal in subgrade and bridge sections, the signal position is not limited by this condition. (6) Meet the requirements of restarting after stopping before the signal. During the operation of the train, it is necessary to ensure that it can brake and stop before the signal point with the target speed limit of

180

5. Optimize control method of train control system

0 km/h. Therefore, when arranging the signal point, it is also necessary to ensure that the train can restart after stopping at the signal point, otherwise the signal point is not allowed to be arranged at this position. The meaning that the train can restart includes two aspects: one is that the starting traction force of the train is greater than the starting resistance of the train; second, the running speed after starting can exceed a given speed. (7) Meet the requirements of section and station tracking interval. The train tracking interval is the minimum interval that the following train is not disturbed by the preceding train. In order to ensure the carrying capacity of the line, during train tracking operation, it is necessary to meet the requirements of the given tracking train interval in the section, that is, the maximum value of each tracking interval generally cannot exceed the given tracking train interval.

5.3.2 Optimization model of section signal point layout The optimal design of block section was first proposed by D.C. Gill and CJ. Goodman in 1992 [20], which aims to use the powerful processing ability of modern computer to change the manual determination of signal point position to the automatic determination of signal point position by computer, so as to realize the optimal layout of signal points. D.C. Gill and C.J. Goodman transform the position of signal points into the solution of nonlinear multiobjective and multiconstraint optimization problem. After establishing the signal point layout optimization model, the model is solved by genetic algorithm, particle swarm optimization algorithm and other optimization algorithms to obtain the optimal layout position of signal points. The method for solving the optimal layout position of signal points is based on the train traction calculation and the principle of section signal layout [21]. In recent years, some scholars have proposed a method for solving the optimal layout position of signal points based on the “blocking time” theory [16,22]. Here, we mainly introduce the former method. 5.3.2.1 Objective function The layout of section signal points is an optimization problem under multiple constraints. The constraint conditions affecting block section design should be satisfied first, and the optimization objectives mainly include safety, efficiency and economy. Safety: safety is the first priority of railway transportation. Ensuring the safe operation of trains is the most important function and goal of railway signal system. The layout of section signal points must meet the safety constraints of train operation.

5.3 Optimization method of block section design

181

Efficiency: safety and efficiency are inseparable in the design of block section. While considering the safety of train operation, it is necessary to ensure the traffic operation efficiency, try to find the balance point between safety and efficiency, and find the optimal layout scheme. Cost: equipment investment is required. For the design of section, each additional track circuit division point will increase the corresponding equipment investment. Therefore, the demand for saving equipment investment in practice should also be considered in the design of section signal layout. Safety, efficiency and economy restrict each other, and corresponding optimization objectives shall be determined during the design of section signal points. As shown in Fig. 5.22, the two adjacent stations are station A and station B. It is assumed that the number of signal points between the two stations is N, xi is the position of each signal, the position of reverse home signal of station A is x0, the position of home signal of station B is xN + 1, li is the length of each block section, and the section has a total of N + 1 block sections. Under the constraints of signal point division, the objective functions are the shortest train operation interval and the least number of signal points. The layout design of section signal points shall be carried out under the conditions of the factors such as train operation safety, train tracking interval and limit length of track circuit. Establish the interval signal point division objective function under “efficiency” and “economy,” which is described as:  min In (5.19) min N where In is the train interval of the nth design scheme, and the optimization objective is the minimum value of all design schemes. The definition and calculation method of In ¼ max{(I1, I2, …IN + 1), IJ, IF, IT} are the same as Section 5.2.1.1. 5.3.2.2 Constraint condition The layout of section signal points in the signal system is mainly considered from two aspects: the position of signal points and the length of each track section. The influencing factors include the maximum

FIG. 5.22

Schematic diagram of section signal point design.

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5. Optimize control method of train control system

allowable train speed, effective braking distance, line environment, limit length of track circuit, train operation interval, adopted train operation organization mode, train operation control system, block system, position of relevant equipment, etc. The constraint conditions are established according to the factors affecting the design of interval signal points: (1) Boundary conditions of signal points: all signal points in the interval must be within the specified boundary range, as shown in the following formula. x0  xi  xN+1 xi1  xi

(5.20)

(2) Length constraints of block section: the length of block section in CTCS-3 high-speed railway is usually set at about 2000 m, Lmax is generally not greater than 3000 m, and Lmin is not less than 1500 m except for the incoming approach section and the first departure section: L min  Li  L max

(5.21)

where Li represents the length of block section at the xi signal point, i ¼ 2,3, …, N2. (3) Transmission length limit of track circuit. The position of section signal point shall be the dividing point of track circuit. Too long track circuit length will lead to excessive attenuation and affect the reliability of track circuit. Therefore, the maximum length of section track circuit shall not exceed the limit transmission distance of track circuit. The length of high-speed railway block section is large. Generally, one block section consists of two track sections. The length of track section must be less than the limit transmission distance of track circuit. The limit transmission distance of track circuit is determined according to the line environmental conditions, as shown in Table 5.8.

TABLE 5.8 Limit transmission distance of track circuit. Line condition

Bridge

Ballastless subgrade

>2000 m

Tunnel 300–2000 m

0 + Lf + Ls

(5.25)

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5. Optimize control method of train control system

(6) Position of signal in approach section of station. The train arrival tracking interval is one of the main factors limiting the carrying capacity. It is necessary to set an appropriate position of the second approach signal point to meet its interval standard. xj  xcj

(5.26)

where xj is the position of the second approach signal point and xcj is the lower limit position of the second approach signal point, which is calculated by the standard of train arrival tracking interval. (7) Conditions of train neutral zone. The neutral zone is an area without traction power. When the train passes through the neutral zone, it completely depends on coasting. Therefore, the following conditions shall be met in the design of signal points. The signal cannot be set in the neutral zone. Fs is the beginning of neutral zone, that is, the position of the forced power-off sign, and the end of the neutral zone, that is, the position of the power-on sign, is Fe: xi 62½Fs , Fe  The signal point before the beginning of neutral zone shall meet the requirements that the train can accelerate to pass through the neutral zone at a speed greater than the specified speed vf after the signal point is restarted: pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi (5.27) 2aðFs  xi Þ  20  vf The signal point after the end of neutral zone shall meet the following requirements: xi  Fe  Sf

(5.28)

where vf is the minimum limited speed passing through the neutral zone, taken as 30 km/h; Sf is the minimum length from the end of neutral zone to the front signal point, taken as 300 m. (8) Train operation interval conditions. The train operation interval after design of section signal points shall meet the given tracking interval (H) to ensure transportation efficiency.

In  H

(5.29)

where In is the train track interval of the nth design scheme, and H is the train track interval specified in the design.

5.3 Optimization method of block section design

185

5.3.2.3 Model solving algorithm Common model solving algorithms include genetic algorithm, particle swarm optimization algorithm, heuristic algorithm, etc. here, the solving process of genetic algorithm is introduced, and the solving steps are shown in Fig. 5.23. (1) Determine the coding scheme. The chromosome with length of n + 1 (x0s ,x1s ,…, xns ) is used to represent a set of block signal layout scheme. Each individual gene in the chromosome xis(i ¼ 0, 1, …, n) represents the position of section signal points, and xis is encoded in the form of real number. (2) Initial population generation. To obtain high-quality initial population through the initial population generation algorithm [23], the convergence speed of the algorithm can be improved. The initial population generation algorithm is shown in Fig. 5.24, in which the coding range R is set at 200. (3) Determine the fitness function. In the process of evolution, genetic algorithm searches through the individual fitness of the population, so the selection of fitness function directly affects the convergence speed of genetic algorithm and the search for the optimal solution. The fitness function shall be combined with the biological evolution mechanism to make the chromosomes with high fitness continue to reproduce and evolve, and the efficient calculation shall be realized through the simple function design as far as possible. The following formula is a reference to the fitness function.

Start Create initial population Select operation Cross operation Mutation operation Fitness calculation Meet termination criteria ? Output optimal individual End

FIG. 5.23

Basic steps of genetic algorithm.

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5. Optimize control method of train control system

Start Set the population size N, M = 1 Random generation n+1 j=n+1, k=1 A chromosome gene was randomly generated in the range of [j·k-r, j·k+r] k=k+1 k>n+1 ? M=M+1 M>N ? End

FIG. 5.24

Initial population generation Algorithm.

fitness ¼

1  1 + k  fit1  fit2  fit3  max I 1 , I 2 , …, I n , I a , I d , I p fit1 ¼ α

fit2 ¼ β

n h X i¼1

n X i¼1

 max 0, xi1  xis s

(5.31)





i max 0, l min  lib + max 0, lib  l max

fit3 ¼ γ

n X i¼1

"





max 0, Sxb i + lf + ls 

(5.30)

t +X N code i¼t

(5.32)

# lib

(5.33)

where k is the constant set to ensure the solution accuracy; fit1, fit2 and fit3 respectively represent the impact on individual fitness value when the signal point layout order is wrong, the length of block section does not meet the design specification and braking distance; α, β and γ are penalty factors. (1) Selection, crossover, mutation and other genetic operations. (2) Determine the algorithm termination conditions. The commonly used algorithm termination condition is given the maximum number of iterations (NG), when the program runs NG times, it ends and outputs the optimization result.

References

187

In order to reduce the influence of block section length on train speed and tracking interval under the condition of long downhill, Gao et al. rearranged the position of signal points under the condition of constant existing signal points by using the block section design optimization method. The results show that, compared with the traditional signal layout, the block section optimization design method can effectively shorten the train section tracking interval of about 20% and the section operation time of 3% on the premise of ensuring the safe operation of trains, so as to improve the line operation efficiency and carrying capacity [23], which verifies the effectiveness of the block section optimization design method.

References [1] China State Railway Group Co., Ltd., Technical Management Regulations for Railways (High-Speed Railway), China Railway Publishing House, Beijing, 2018. [2] J.F. Wang, H. Zhang, R.W. Kang, et al., An adaptive dynamic coding method for track circuit in a high-speed railway, IEEE Intell. Transp. Syst. Mag. 14 (3) (2021) 188–199. [3] H. Zhang, J.F. Wang, X.Y. Zhang, et al., A method on improving the carrying capacity for CTCS-3 railway, IEEE Intell. Transp. Syst. Mag. 13 (3) (2020) 118–130. [4] J.F. Wang, Traffic ability impact analysis about different train control system on the same passenger dedicated line, J. Beijing Jiaotong Univ. 34 (06) (2010) 1–4. [5] D. Emery, Headways on high speed lines, in: World Congress on Railway Research, 2011. [6] B. Hunuadi, Capacity Evaluation for ERTMS Level 2 Operation on HS2, Bombardier Transportation, Berlin, 2011. [7] Y.S. Zhang, C.H. Tian, X.L. Jiang, et al., Calculation method for train headway of high speed railway, China Railw. Sci. 34 (05) (2013) 120–125. [8] C.H. Tian, S.S. Zhang, Y.S. Zhang, et al., Study on the train headway on automatic block sections of high speed railway, J. China Railw. Soc. 37 (10) (2015) 1–6. [9] Y. Yin, L. Liu, J.G. Zhang, Train pre-decelerating before arrival station, J. Transp. Eng. Inform. 5 (02) (2007) 84–88. [10] F.H. Wei, Q. Wu, L. Liu, Simulating calculation and optimization design of the tracing time interval of trains in aim-interval control mode, J. Transp. Syst. Eng. Inf. Technol. 7 (3) (2007) 105–110. [11] G.Y. Lu, Z.L. Shen, Q.Y. Peng, et al., Compressing arrival interval of high-speed trains by speed control within railway section, J. China Railw. Soc. 43 (01) (2021) 19–27. [12] D.W. Yan, C.Y. Wang, Optimization and Simulation Research on the High-Speed Rail Train Tracking Interval, ICTE, 2019. [13] J.C. Geng, Analysis of influence of neutral zone on train tracking interval time of high-speed railway, China Railw. 10 (2011) 7–10. [14] L. Liu, D.Y. Wei, Y. Yin, Mechanism and calculation of speed-interval control of high-speed passenger trains, J. Southwest Jiaotong Univ. 41 (05) (2006) 575–581. [15] R. Takagi, Synchronisation control of trains on the railway track controlled by the moving block signalling system, IET Electr. Syst. Transp. 2 (3) (2012) 130–138. [16] E. Quaglietta, A simulation-based approach for the optimal design of signalling block layout in railway networks, Simul. Model. Pract. Theory 46 (2014) 4–24. [17] H.D. Liu, B.H. Mao, B.S. Wang, et al., Optimization of high-speed railway section signaling layout based on new differential evolution algorithm, J. China Railw. Soc. (05) (2013) 40–46.

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[18] National Railway Administration, TB/T 3516-2018 General Technical Specification for CTCS-2 Train Control System, China Railway Publishing House, Beijing, 2018. [19] S.G. Zhang, General Technical Specification for CTCS-3 Train Control System, China Railway Publishing House, Beijing, 2008. [20] D.C. Gill, C.J. Goodman, Computer-based optimisation techniques for mass transit railway signalling design, IEE Proc. B 139 (3) (1992). [21] H.D. Liu, B.H. Mao, B.S. Wang, Optimization of railway section signalling layout based on quasi-moving block, J. Transp. Syst. Eng. Inf. Technol. 11 (4) (2011) 103–109. [22] V. Vignalia, F. Cuppia, C. Lantieri, A methodology for the design of sections block length on ETCS L2 railway networks, J. Rail Transp. Plann. Manage. 13 (2020) 100160. [23] G.L. Gao, J. Zhang, X.J. Yang, A study on the high speed railway signal block layout for long downhill grade line, Railw. Transp. Econ. 42 (2) (2020) 73–80.

C H A P T E R

6 Shorten the tracking interval through the control algorithm 6.1 CTCS-3I train control system with moving block function 6.1.1 Principle of moving block The moving block adopts the speed control mode of one-time braking. The tail of the previous train is the tracking target, and a safety protection interval is maintained with the forward train. Through accurate train positioning technology, the position of the train is determined in real time, the actual distance between the train and the front train is calculated, and the distance is transmitted to the on-board equipment through vehicle–ground two-way communication in real time, which calculates the best braking time of the train in real time [1]. In the moving block system, the logic of block section is only insures the safe running intervals of the trains. There is no corresponding relationship between the actual circuit and block section. Therefore, there is a big difference between moving block on the design and fixed block, the train positioning technology, and target, and the safety distance is moving block three basis points. (1) Train positioning technology Train location is the basis of moving block technology. To realize moving block technology, first of all, the location information of trains must be grasped accurately in real time to determine the relative distance between trains. The train control system constantly compares the actual distance between trains with the required distance between trains to determine the safe running speed of trains. Train positioning is completed by ground equipment and onboard equipment, usually the axle of the train wheels are installed on tachometer to determine the direction and distance of the train, once determined, the starting point of the train operation,

Theory and Technology for Improving High-Speed Railway Transportation Capacity https://doi.org/10.1016/B978-0-323-99700-3.00003-7

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Copyright © 2023 Elsevier Inc. All rights reserved.

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6. Shorten the tracking interval through the control algorithm

according to the train running direction of the wheel tachometer is detected and go line distance can accurately determine the actual location of the train. However, due to the measurement error of onboard equipment positioning equipment, especially after the train runs for a long distance, the error will continue to accumulate and directly affect the accuracy of train positioning, so it is necessary to install one ground positioning equipment every fixed distance on the line. When the train passes these ground positioning equipment, the vehicle sensor can detect the location point to obtain the exact position of the train, so as to eliminate the accumulated positioning error caused by the onboard equipment positioning equipment. Train location technology mainly includes track circuit location, axle location, speed location, query-transponder location, GPS location, wireless spread spectrum train location, inertial train location system, dead reckoning system location, map matching location, etc. (2) Target point The target point is usually located at a certain distance in front of the train, once set, it indicates that the train can safely run to the point, but not beyond the point. Moving block system guides the train to run safely on the line by continuously moving forward the target point of the train. If the train is running on the section without a switch of the line, the target point for tracking train is a safe distance from the rear of the train ahead, as shown in Fig. 6.1, if the train in front stops, the target point of the tracking train stops at this point. When the train runs to one common braking distance from the target point, if the braking starts, the train can be guaranteed to stop behind the target point. If the forward train continues to move forward, the target point of the tracking train also moves forward, thus forming a moving block between the trains. As shown in Fig. 6.2, when a train needs to pass a switch, if the switch is not locked at the specified position, the target point of the train is the position of one safe distance (TPb) ahead of the switch. When the switch is converted and locked to the specified position, the target point can cross the switch area and move to the TPc behind the switch. After the train gets

The railway stops behind the target point

FIG. 6.1 Schematic diagram of target point determination in the section without a switch.

191

6.1 CTCS-3I train control system with moving block function

SW

SW TPb

TPc

FIG. 6.2

Schematic diagram of switch target section

the target point, it can pass the switch to realize the interlock between the train operation and the switch and ensure the safe running of the train in the switch area. (3) Safe distance The safety distance is an additional distance calculated based on the train safety braking model, which ensures that the tracking train can safely stop behind the moving train without collision under the most adverse conditions. Therefore, the safety distance is the key in the moving block system and the theoretical basis and safety basis of the whole system design. As shown in Fig. 6.3, it is assumed that the tracking train T1 is running at the maximum speed allowed by the line at point A, while the forward train T2 is at point E. Normally, the tracking train starts the usual braking, along the braking curve D, and stops at point B. However, if the tracking train T1 fails at this time, it does not start braking but accelerates with speed a

b

service braking curve

emergency brakingcurve d

c

C

A

FIG. 6.3

service braking distance

E B safe distance

Schematic diagram of safe distance.

distance

192

6. Shorten the tracking interval through the control algorithm

maximum acceleration until the on-board controller detects that the train speed exceeds the allowable range, such as curve section A. After that, the onboard controller activates the train’s emergency braking system, and the train runs along curve B for another distance before the emergency braking force takes effect. Then the braking force takes effect and the train stops at point C along curve C with emergency braking. Considering the uncertain factors such as the positioning error and speed measurement error of the train, the actual stop position of the train may also BE point E. Therefore, the distance of BE is called the safe distance.

6.1.2 CTCS-3I system architecture and function CTCS-3I train control system is a train control system based on GSM-R wireless communication system to realize two-way transmission of vehicle–ground information, radio block center to generate MA, track circuit to realize train occupancy check, and transponder to realize train location. The difference between CTCS-3I and CTCS-3 system is that it does not change the physical structure of CTCS-3, but realizes the function of moving block from the perspective of algorithm to replace the existing automatic block and improve the transportation capacity of the line [2]. 6.1.2.1 Ground equipment of CTCS-3I train control system CTCS-3I ground equipment includes: radio block center (RBC), temporary speed restriction server (TSRS), track circuit (TC), train control center (TCC), Balise, and linsinde electronic unit (LEU). Radio block center: generates messages sent to the train based on information provided by ground equipment and interaction with onboard equipment. These messages are primarily used to provide MA for the safe operation of trains on lines within RBC’s jurisdiction; Through the vehicle–ground wireless communication system to transfer the MA and line description information to the onboard equipment of the train within its control area. Temporary rate limiting server: manages temporary rate limiting commands in a centralized manner. The temporary rate limiting server transmits the temporary rate limiting information to the RBC and TCC, respectively. Track circuit: train occupancy check; provide speed information and forward idle interval information for CTCS-3I level backup system. Train control center: realize track circuit coding, interstation safety information transmission and other functions, and transmit train occupancy information to RBC; Temporary speed limit information and route information are transmitted to the CTCS-3 backup system via the linsinde electronic unit and active balise.

6.1 CTCS-3I train control system with moving block function

193

Transponder: Point-type transmission device that transmits messages to on-board devices and provides an uplink, i.e., transmission information from the ground to on-board devices. The transponder can provide fixed information and variable information when connected to the linsinde electronic unit. The transponder can be used in the form of a group, each transponder transmits a message, and the composition of all messages constitutes the information of the transponder group. According to the functional classification, there are transponder groups used to send line parameters, transponder groups used to send grade conversion or RBC switching information, transponder groups used to identify the direction of train operation, transponder groups used for train location, etc. Trackside electronic unit: Electronic device that generates the message to be transmitted by the transponder based on information provided by the ground equipment. 6.1.2.2 On-board equipment of CTCS-3I train control system Train control onboard equipment is the main body of train control system to operate and control the train, which plays an important role in ensuring the safety of train operation and is the key equipment to ensure the safety of train in CTCS-3I train control system. It adopts fail-safe design, generates train speed control curve according to the received ground information and wireless information, and compares it with the actual train speed, supervises train operation, and realizes overspeed protection and man–machine interface display. CTCS-3I vehicle equipment includes: vital computer (VC), track circuit information reader (TCR), balise transmission module (BTM) and transponder antenna, radio transmission module (RTM), display man–machine interface (DMI), train interface unit (TIU), speed and distance measurement unit (SDU), judicial recording unit (JRU). Vital Computer: monitors the safe operation of the train according to the information exchanged with ground equipment and is responsible for handling the control functions of on-board equipment at different levels. Track Circuit Information Reader: receive track circuit information. The antenna of TCR (Track Circuit Reader) receives the electrical signal on the Track circuit, determines the carrier frequency and demodulates the low frequency information, and determines the information code according to the low frequency. TCR has the function of receiving multiple carrier frequencies at the same time, and will select the carrier frequency with the highest level and demodulate the low frequency information modulated in this carrier frequency. The TCR sends the type of carrier frequency received, the low frequency information demodulated, to the on-board vital computer, and the TCR is able to lock the carrier frequency using

194

6. Shorten the tracking interval through the control algorithm

the driver’s bridge direction selector switch (up and down selection on the DMI) and line data from the balise. Balise Transmission Module and Transponder Antenna: The transponder information receiving unit receives information from the ground transponder by connecting to the transponder antenna. And transmits the resulting data to vital computer. Radio Transmission Module: connected with GSM-R vehicle radio to achieve vehicle–ground two-way information transmission. Display man–machine Interface: the display man–machine interface realizes the information interaction between the driver and the on-board equipment. DMI informs the driver of various information of the train and the status of on-board equipment through sound, image and other information, and prompts the driver to perform corresponding operations. DMI has the functions of interface display, driver command input, voice memory, voice playback, communication collection, fault representation and so on. Train Interface Unit: provides the interface between the vital computer and train-related equipment. Speed and Distance Measurement Unit: receives signals from speed sensors and other equipment to measure the running speed and distance of the train. Judicial Record Unit: The judicial record unit is used to record data related to train operation safety and download it for data analysis when needed. 6.1.2.3 Technical characteristics of CTCS-3I train control system CTCS-3I train control system is based on GSM-R car to two-way information transmission on the wireless communication, RBC generate MA, balise to realize train positioning, CTCS-3I train control system’s basic function: to provide safe driving is the necessary information of the train and monitoring the train operation, have automatic phase too much function, can satisfy the demands of cross line running operations, It has the functions of track occupancy check and train integrity check. It adopts moving block to monitor train operation with the continuous speed control mode of target distance. It has two control modes of equipment braking priority and driver braking priority, and generally adopts equipment braking priority control mode. The on-board equipment of CTCS-3I train control system mainly has the functions of speed measurement and ranging, wireless communication management, transponder information reception and processing, speed monitoring, slip and retreat protection, level switching, vehiclemounted equipment working mode selection, human–computer interaction, emergency shutdown message processing and data recording, etc. The details are as follows [3].

6.1 CTCS-3I train control system with moving block function

195

Speed measurement and ranging: train control vehicle equipment and speed measurement and ranging unit, through processing speed sensor pulse and radar signal, on the basis of judging whether the train is idling and skidding, real-time calculation of train running speed and accumulated travel distance. The on-board equipment provides the received transponder group information, corrects the cumulative error of distance measurement, and realizes the precise location of the train. Wireless communication management: Train control onboard equipment interacts with RBC through GSM-R wireless communication system, so onboard equipment needs to manage wireless communication, including wireless network registration, communication session establishment, communication session maintenance, communication session termination and other major processes. Transponder information receiving and processing: train control vehicle equipment obtains wireless registration, grade switching, communication management, position calibration and RBC switching information from the ground transponder group through the transponder information receiving antenna and transponder information receiving unit. Speed monitoring: train control vehicle equipment generates the corresponding dynamic speed monitoring curve according to the line allowable speed, temporary speed limit and MA, and monitors the train operation by comparing it with the train running speed. Slip and reverse protection: slip protection means that the train control onboard equipment will protect the improper movement of the train when the train is stopped. When the train control vehicle detects that the train escape distance exceeds 5 m, the vehicle will immediately implement emergency braking. Backtrack protection: Prevents the train from running in the opposite direction to the permitted direction. When the regression distance is detected to exceed 5 m, the train control onboard equipment immediately implements emergency braking. Curve calculation synchronization technology: In order to ensure smooth transition from grade CTCS-3I to grade CTCS-2 and avoid braking stop caused by allowable speed difference caused by two independent vehicle control modules, they must be synchronized at the level of curve calculation by the following means: (1) Shared speed sensor information: CTCS-3I level car control module and CTCS-2 level car control module synchronously share the speed distance information sent by the speed measuring and ranging unit in broadcast mode through the bus, providing synchronous speed information and position information for curve calculation and speed monitoring

196

6. Shorten the tracking interval through the control algorithm

(2) Synchronous transponder information: Same with the working principle of the speed measuring and ranging unit, CTCS-3I level control module and CTCS-2 level vehicle control module can obtain the synchronized transponder information, which provides the synchronization basis for the subsequent curve calculation and position correction. Man–machine interaction: the driver can input the driver number, train number, train length and other information through the man–machine interface equipment, and carry out mode conversion, grade conversion and other operations; At the same time, DMI provides the driver with the train running speed, target speed, allowable speed, target distance, geographic information, text information, confirmation information, warning information and so on by means of graphics, text and sound. Emergency stop message processing: the on-board train control equipment will process the emergency stop message from RBC. When receiving the unconditional emergency stop message, the on-board train control equipment will output emergency brake and enter the aggressive protection state. When receiving the conditional emergency stop message, the train control vehicle equipment will choose to accept or reject the emergency stop message according to the actual situation, and output the corresponding control command. Data recording: driver operation, vehicle–ground interaction information, brake output and working status of vehicle-mounted equipment are recorded by using the recording unit configured by train control onboard equipment. 6.1.2.4 Carry capacity of moving block Moving block technology will be applied in subway and freight lines, and the capacity of the lines will be greatly improved. At present, moving block are tested on the Qingzang Line and the Shuohuang Line [4]. Shuohuang railroad is an overloaded railway, intend to use moving block technique, it is part of Shenhuang railway, the design annual transport capacity is 350 million tons, forward 450 million tons, is the second translating western coal shipped east China. Under the three-display automatic block mode of Shuohuang Railway, the tracking interval of ordinary cargo train is 9 min, the tracking interval of 10,000 tons train is 12 min, and the tracking interval of 20,000 tons train is 15 min. It is estimated that the train tracking interval will be reduced to 7.3 min after adopting the moving block mode. At the same time, under the condition that the existing locomotive and rolling stock equipment adopts the moving blocking mode and all operate C700,000 tons, the annual transportation capacity of Shuohuang Railway can reach 472 million tons. Compared with the original fixed block of 368 million tons,

6.1 CTCS-3I train control system with moving block function

197

the annual transport capacity is increased by 104 million tons. Compared with the fixed block, the moving block driving mode has a significant effect on the improvement of transport capacity, which is an important measure for the improvement of heavy-haul railway transport capacity [5]. Moving block can be an important measure to improve the capacity of single track railway. Taking Gla section of Qingzang Line as an example, after moving block is implemented in Gla section, the line passing capacity is 12 pairs every day for passenger trains and 10 pairs every day for cargo trains, a total of 22 pairs every day [6]. According to the existing results, the passing capacity of ordinary block, automatic block and moving block can be obtained in the Gla section of Qinghai-Tibet Line, as shown in Table 6.1.

6.1.3 CTCS-3I Train control software Execution process In terms of transport capacity, CTCS-3I adopts moving block control mode in the process of train running, compared with three display automatic block system, Interval passing capacity increased by at least 30%, generally up to 25%. Moving block train Control System CTCS-3I is based on the existing CTCS-3 system. By modifying the software control algorithm without adding any hardware devices, the moving block is realized. The target point of train tracking is changed from the beginning of the existing track circuit to the tail of the forward train, so the train tracking interval is shortened. The execution process of CTCS-3I train control software is as follows: (1) At the designated location after the train leaves the warehouse, After registering with the GSM-R wireless network, the on-board device establishes a communication session with the RBC and sends the registration request，RBC will complete the train registration after the corresponding train is identified by the dispatching center CTC. When sending the registration application, First, when passing through the passive transponder, the onboard wireless transmission TABLE 6.1 Carry capacity of lower Gla section in different block types. carrying capacity Block type

passenger train

Freight train

add

inter-station block

6

6

12

automatic block

10

10

20

moving block

12

10

22

198

6. Shorten the tracking interval through the control algorithm

unit RTU calls to establish the GSM-R channel. DMI, the operation interface of the onboard equipment, sends the train ID, train number, train length and stored train parameters entered by the driver to RBC to apply for registration. RBC forwards the train number information to CTC for train identification and train registration. The GSM-R digital communication of CTCS-3 can meet the requirements of moving block in terms of transmission mode, amount of information, rate and delay. When the GSM-R communication is interrupted for longer than the specified time, the on-board equipment applies the usual braking, while CTCS-3I uses the backup system, degraded operation. (2) After the train starts running, the on-board equipment collects and transmits the train operation data in real time, calculates the target distance according to the principle of moving block, completes the integrity check of the train, and generates the moving authority. The on-board equipment determines the train position and measures the train speed, and sends the train position, train speed, train integrity information, train status and on-board equipment status to RBC via wireless network. The train obtains the license to run within the current RBC control range, calculates the allowable speed of all positions of the train within the license area, generates the continuous speed control mode curve of the target distance, and monitors the safe operation of the train. With the train moving forward, RBC extends the train moving authority by using the movement authority generation algorithm according to the approach information provided by the interlocking CBI and the idle information of block partition, and completes the movement authority among different RBC. Switch to the backup mode for train control when the preset condition is reached. After the train is authorized to run within the current RBC control range, CTC orders the interlocking system CBI to handle train access according to the running plan. RBC and CBI divide the line between stations into several signal-authorized SA segments, and then conduct information exchange with the signal-authorized SA segment and incremental distance. CBI sends signal authorization SA and train integrity information to RBC based on access information and track circuit status. RBC generates driving permission MA based on SA and incremental distance, train position and running direction, and sends MA to on-board equipment. (3) On-board equipment and On-board safety computer software can calculate the allowable speed of all train positions within the driving permit area, generate the continuous speed control mode curve of target distance, and monitor the train speed of vehicle-mounted equipment, including ceiling speed monitoring CSM and target speed monitoring TSM. Under the monitoring of CSM and TSM, the generated continuous velocity control mode curves of target distance are static velocity curve and dynamic velocity curve respectively.

6.2 CTCS-3I dynamic velocity curve algorithm

199

Dynamic speed curve corresponding to the TSM, including allowing speed curve, alarm, speed curve, common braking curve and emergency brake curve, on-board equipment according to the traction model, brake model, slope and adhesion conditions determine train under various circumstances and the position of braking deceleration, according to the length of the train to the rear of the keep the distance, Thus, alarm speed curve, common braking curve and emergency braking curve are calculated.

6.2 CTCS-3I dynamic velocity curve algorithm Ceiling speed monitoring CSM and target speed monitoring TSM track the target point to the rear of the car in front. Dynamic speed curve includes service braking curve and emergency braking curve. From the perspective of railway signal, the transport capacity can be improved by shortening the tracking interval between trains by optimizing dynamic speed curve.

6.2.1 ATP protection curve algorithm of CTCS-3I train control system Under the monitoring of CSM and TSM, the generated continuous velocity control mode curves of target distance are static velocity curve and dynamic velocity curve respectively. For CSM, the calculation of static speed curve includes allowable line speed (determined by line grade, slope, bend, bridge, tunnel speed limit, etc.), temporary speed limit, and speed class for specific trains, which are determined by infrastructure equipment (such as lines, Bridges, tunnels, etc.) and train attributes, structures, and their own conditions. Vehicle equipment is calculated according to line data and train parameters. When the ceiling speed monitoring curve is at a higher speed limit level, the train should meet the requirements of a lower static speed curve until the end of the train also enters a higher speed level section. When the ceiling speed monitoring curve is a lower speed limit class, the front end of the train should meet the requirements of dynamic speed curve. For TSM, dynamic speed curve including allowing speed curve, alarm speed curve, service braking curve and emergency brake curve, on-board equipment determine train under various circumstances and the position of braking deceleration according to the traction model, brake model, slope and adhesion conditions, Determine the distance the rear of the train should keep according to the length of the train, thus, alarm speed curve, service braking curve and emergency braking curve are calculated.

200

6. Shorten the tracking interval through the control algorithm

Service brake curve

Emergency brake curve

Train1

Train2

LSB

LS

Lr

FIG. 6.4 Dynamic velocity curve of CTCS-3I.

As shown in Fig. 6.4, the service braking curve is the braking curve obtained when the train speed exceeds the preset speed threshold and the on-board device applies braking when the actual speed is lower than the allowable speed. Emergency braking curve refers to the braking curve obtained after the train speed exceeds the preset speed threshold and the onboard equipment adopts emergency braking and relieves braking after the train stops.

6.2.2 ATP protection curve algorithm of CTCS-3I train control system ATP safety braking curve design is one of the key technologies of on-board ATP system. Due to the speed and capacity limitation of on-board computer, curve calculation in some train control systems adopts European standard method to simplify calculation. European standard method divides deceleration in braking process into 6 steps at most. Each step corresponds to a constant deceleration, which will cause the phenomenon of uneven distribution of safety margin. Moreover, the value of deceleration in European standard method is conservative, which affects the transportation efficiency and carry capacity of railway [7]. Based on the calculation principle of The European standard method, this section uses the speed step boundary optimization algorithm of the European standard method to obtain the carry capacity of trains under different line conditions and braking performance in order to maximize transportation efficiency and minimize the fluctuation of safety margin [8].

201

6.2 CTCS-3I dynamic velocity curve algorithm

6.2.2.1 Calculation model of European standard method In the braking process, the main forces of the train are braking force, basic resistance and line additional resistance. In the process of train movement, the resultant force changes with the change of speed, not a constant value. The braking process is subdivided into M speed steps V by the theoretical method, as shown in Fig. 6.5. Assuming that the combined force of train deceleration is unchanged within this step, the distance increment S within the speed step V is calculated by combining the kinematics equation, and the inverse calculation is carried out from the protected target point according to the step size. And the standard method only consider the train speed and deceleration ramp resistance reduction, and a ladder in the same speed train speed and reduction in the same slope gradient resistance reduction rate remains the same, so the train only in changing slope point and resultant force reduction speed ladder boundary value changes, as shown in Fig. 6.6, according to the changes of the train together deceleration, braking process can be divided into M phases, The resultant deceleration is constant in each braking stage. From the protected target point, the velocity increment V and displacement increment S of each braking stage M are calculated backwards. Assuming that the slope of the jth slope is wi(j) and the slope change point is Lj(j¼1, 2, … , J), the braking process is divided into K speed steps, The boundary value of each velocity step is Vk(k¼1, 2, … , k), V0¼0 km/h, (Sm(1),Vm(1)) Speed km/h

(Sm-1(1),Vm-1(1))

Vm(1)-Vm-1(1)

Sm-1(1)-Sm(1)

FIG. 6.5

Theoretical method Reverse calculation by step size.

Distance(m)

202

6. Shorten the tracking interval through the control algorithm

Lj Wi(j)

Lj-1

Speed Km/h

ramp

(Sm,Vm) (Sm-1,Vm-1) Vk

Vk-1 … …

… …

Protection period

SK The mth segment

Distance/m

Protective target point

FIG. 6.6 European standard method reverse calculation according to the braking stage

Vk¼350 km/h), projected to the displacement direction is the boundary point Sk, and the corresponding train deceleration in the kth speed ladder(Vk-1, Vk) is ak. In order to ensure driving safety, this paper takes the minimum value of train deceleration in this speed range. ak ¼ min ðbðvÞ + 0:0098w0 ðvÞÞ vðV k1 , V k 

(6.1)

In Formula (6.1), b(v) refers to train braking and deceleration; w0(v) is the basic resistance of the train. In Fig. 6.6, the demarcation point of the mth braking stage on the curve,(Sm, Vm), can be calculated by inverse calculation of (Sm-1, Vm-1)
 Sm ¼ min Sp , Lq (6.2)   qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
 (6.3) V m ¼ min V p , 2cm Lq  Sm1 + vm1 2 In Eqs. (6.2) and (6.3), Lq represents the boundary point of the m braking stage, Sm is the change point of resultant deceleration nearest to the next boundary point Sm-1, Sp is the projection of the boundary value of the speed ladder in the displacement direction, cm is the resultant deceleration of the m braking stage. cm ¼ ap + 0:0098wi ðqÞ

(6.4)

6.2 CTCS-3I dynamic velocity curve algorithm

203

In Formula (6.4), resultant deceleration cm is composed of train deceleration ap and additional ramp resistance .wi(q) Taking the protection target point as the starting point, reverse calculation is carried out according to the braking stage m to obtain the braking distance S and braking time T of the train, i.e., S¼

M X

ΔSm

(6.5)

Δtm

(6.6)

m¼1

T¼

M X m¼1

6.2.2.2 Optimization model In order to ensure driving safety, the deceleration in the speed ladder is taken as the minimum deceleration in the speed range. This causes two problems: first, the conservative value of deceleration loses the curve efficiency and affects the transportation efficiency and passing capacity of railway; Second, the constant value of deceleration in the speed ladder results in the uneven distribution of safety margin. Due to the conservative value of train deceleration in the European standard method, the braking time of the curve from the braking starting point to the protection target point will increase compared with the theoretical method. Here, the proportion of increased braking time is defined as curve efficiency loss, and the calculation formula is as follows. U¼

T  T ð0Þ T ð0Þ

(6.7)

In Formula (6.7), T(0) and T are the braking time of theoretical curve and European standard curve respectively. When train braking performance and line conditions are constant, the theoretical curve braking time is constant and always less than the curve braking time of European standard method. Therefore, the smaller the efficiency loss U is, the less the European standard curve braking time is, the better the corresponding speed step boundary value scheme is, and the higher the passing ability is. In Formula (6.8), safety margin Rm is defined as the difference between the theoretical curve and the European standard curve, that is, the ratio of ðV m ð0Þ  V m Þ to the theoretical curve speed limit ðV m ð0Þ Þ. Rm ¼

vm ð0Þ  vm vm ð0Þ

(6.8)

The smaller the fluctuation of safety margin means that the relative difference level of the two curves is relatively stable, indicating that the safety reliability of the curve design of European standard method is also higher,

204

6. Shorten the tracking interval through the control algorithm

and the corresponding speed step boundary value scheme is better and the passing ability is higher. In this paper, the fluctuation of safety margin is represented by the standard deviation of each initial speed safety margin in the braking process, and the minimum standard deviation of safety margin and the minimum curve efficiency loss are two optimization objectives to build the European standard method speed step boundary value optimization model.

6.2.2.3 Genetic algorithm Genetic algorithm has the ability to search global optimal solution quickly and can deal with complex nonlinear system optimization problems. This paper adopts genetic algorithm to solve, and the basic steps are as follows: Step 1: Chromosome coding. The parameter to be optimized for the model is the boundary value of the speed ladder Vk. Since the speed boundary value Vk needs to be arranged from small to large, if the Vk is encoded in sequence 0–1, it is easy to produce a large number of infeasible solutions in the operation of chromosome crossover and mutation, affecting the evolutionary efficiency of the optimal solution. The value range of Vk is the speed interval (Vk-1, Vk), which can be linearly transformed to the interval (0,1) by eq. (6.9). θk ¼

V k  V k1 V K  V k1

(6.9)

Step 2: Initial population generation. Set population size as 0 and randomly generate K-1 positive integers (0, 350) that are not equal to each other. Step 3: Calculate the population fitness function. The optimization model constructed in this paper is a minimization problem. During each iteration, the target values y1 and y2 of the model are calculated, and the fitness of each chromosome is calculated.

Fitness ¼ λ1

f 1 ¼ 1=y1

(6.10)

f 2 ¼ 1=y2

(6.11)

f 1  f 1min f 1max  f 1min

+ λ2

f 2  f 2min f 2max  f 2min

(6.12)

Equations (6.10) and (6.11) transform the model into a maximization problem. Equations (6.12) normalize the dual objectives to calculate the population fitness. λ1 and λ2 are the weight coefficients of the two objectives. Step 4: Update the population. The operation of population renewal includes selection, crossover and mutation.

205

6.2 CTCS-3I dynamic velocity curve algorithm

Step 5: Determine termination conditions. Judge whether the number of iterations meets the requirement of the maximum number of iterations, if so, output the calculation results; Otherwise, return to Step 3. Since the selection of the boundary value of the speed ladder of the European standard method is an offline problem, the solving time of the genetic algorithm can meet the requirements [9]. The speed limit calculated by vehicle equipment, line conditions and train braking performance are three key parameters that affect the setting of speed threshold. The law of setting the boundary value of the speed ladder under the variation of the above three parameters is discussed. (1) Calculation speed of onboard equipment The larger the number of European standard speed steps k is, the longer the curve calculation time is, and the higher the requirement on the calculation speed of vehicle equipment is. Here, the number k of speed steps is sensitized, and the boundary value schemes of speed steps under different k values are given to adapt to different computing capabilities of onboard devices, as shown in Table 6.2. As can be seen from Table 6.2, as the number of speed steps increases, the calculation time grows faster and faster, while the calculation speed of onboard equipment is about 140 m/s. This verifies that the speed ladder should not be too many, choose 6 sections at most. When the number of steps is less than 3, the efficiency loss is up to 17.6%. This shows that it is necessary to set the number of speed steps reasonably according to the calculation speed of onboard equipment, in order to achieve a higher level of unity in both calculation efficiency and curve efficiency. (2) Line conditions The line conditions were set as 35%, 20%, 10%, 10%, 15%, and 20% ramps, respectively, to explore the change rule of the boundary value of the speed ladder when the slope changes, as shown in Table 6.3. When TABLE 6.2 Decomposition value schemes of speed steps at different number of speed steps K.

Number of steps

Boundary value/(km/h)

6

17

99

158

222

5

16

110

179

250

4

15

124

232

3

12

180

2

186

279

Fitness y1/% y2/%

Operation 10 times timeconsuming

0.9298

4.18

0.27

0.1472

0.9160

5.18

0.29

0.1229

0.8943

6.85

0.30

0.1153

0.8175

10.71 0.90

0.1102

0.6855

17.62 2.02

0.1089

206

6. Shorten the tracking interval through the control algorithm

TABLE 6.3 Boundary value schemes of speed steps under different line conditions. Gradient/% Boundary value/(km/h)

Fitness

y1/%

y2/%

35

17

101

163

228

292

0.8279

10.56

0.74

20

17

99

162

220

286

0.8911

6.54

0.44

10

17

99

156

217

284

0.9122

5.25

0.34

0

17

99

156

216

283

0.9269

4.38

0.28

10

17

99

154

214

283

0.9367

3.77

0.24

15

17

99

154

215

282

0.9404

3.53

0.23

20

18

98

147

209

277

0.9440

3.30

0.22

the line slope fluctuates within the range of 20% to 15%, the boundary values of the speed ladder are basically the same. When the ramp is 15% to 20%, the boundary value of the speed ladder decreases by 5 to 10 km/h. When the slope is 20% to 35%, the boundary value of the speed ladder increases by 6 to 8 km/h. This indicates that the optimized boundary value of the speed ladder is relatively stable within a certain range of slope variation, but when the slope is greater than 10% or less than 20%, it is necessary to reoptimize the design of the boundary value of the speed ladder. According to the relevant technical standards of China, the average slope of the line is generally within 20%, so the optimized speed step boundary value scheme has good applicability and stability. In this chapter, by optimizing the design of the boundary value of the speed ladder of European standard method, the setting rules of the boundary value of the speed ladder under different line conditions and train braking performance are obtained. The case results show that the optimized European standard curve safety margin volatility is reduced by 2.83%, the efficiency loss is reduced by 5.66%, and the carry capacity is improved.

6.2.3 Optimization of overspeed protection curve based on train braking performance At present, there are three main methods to calculate the overspeed protection curve: inverse algorithm, direct calculation method and twoway recursive algorithm. The direct calculation method is the most close to the reality, but the steps are too tedious, requiring a lot of repeated iteration operations; The process of bidirectional recursive method is simple and easy to calculate, but it needs to find the intersection point by drawing, so the accuracy is not high. The reverse algorithm combines

6.2 CTCS-3I dynamic velocity curve algorithm

207

the characteristics of the above two methods, through pure mathematical means, makes full use of the characteristics of fast repeated operation in computer processing, and finds the actual calculation method. In this chapter, the variable step size ΔT inverse algorithm, ΔV inverse algorithm and ΔS inverse algorithm are used to calculate the overspeed protection curve, and the calculation accuracy of different methods is obtained. 6.2.3.1 Simulation algorithm principle of ATP protection curve The algorithm of target distance pattern curve is based on the calculation of train safety braking distance [10]. The calculation of train safe braking distance involves the calculation of train traction. Since ATP protection curve calculation does not involve the traction condition, only braking force and resistance are used in the traction calculation. The principle of the inverse algorithm is shown in Fig. 6.7 below. Given the distance between the train and the target stopping point or deceleration point, that is, the target distance is DT, the piecewise iterative method can be used to calculate the speed control curve. The section of length DT is equally divided into n small segments of length Δs and is calculated from the target velocity of the known target point to the opposite direction of the higher velocity. From Fig. 6.7, it can be seen that starting from the nth Δs cell segment, make the final braking speed vt of this segment equal to the target speed vT. If ΔS is selected as the step size and substituted into the equation, the initial braking speed of this section, V0 can be calculated. Let the final braking speed of the adjacent (n  1)th ΔS is the initial braking speed of the nth section, calculate the initial braking speed of the (n  1) section, and so on. When n is large enough, the speed point forms a smooth speed curve. 6.2.3.2 Algorithm flow is described as follows (1) According to the received track circuit information, determine the target distance point DT and target speed vT of the braking curve; (2) Let i ¼ 0, vi ¼ vT, si ¼ DT to determine the initial speed and displacement of the braking curve. (3) According to the displacement and line data, determine the most limited speed at this position, and determine the most limited speed vlim for this calculation; (4) Judge whether vi is less than vlim, if vi < vlim, then judge whether vi is less than vts (vts is the speed boundary value of step from Δt to ΔS), If vi  vts, vi + 1 ¼ vi + aΔs, si + 1 ¼ si  (vi  Δt + (Δt) 2/2), If vi > vts, si + 1¼ si–Δs. (5) If vi vlim, vi + 1 ¼vlim, si + 1 ¼si–Δs. (6) Let i ¼ i + 1 to judge the size of i. If i < N, return to Step 3.

208

6. Shorten the tracking interval through the control algorithm

Velocity

Vlim v2

The (n-2)th ΔS segment v1

The (n-1)th ΔS segment v0

ΔS

The nth ΔS segment

ΔS

vT

DT

Distance

FIG. 6.7 Inverse algorithmic process.

6.2.3.3 Simulation calculation of train running resistance In the process of ATP curve simulation, certain line parameters need to be selected. Two stations and one interval are selected for line parameters, including line length, ramp, bend, tunnel and maximum speed limit, etc. Emu data include marshaling length, mass, unit resistance, traction characteristics and braking characteristics. In the process of train operation, the resistance to the train running direction caused by mechanical friction, air friction, ramp, curve and other factors can be divided into basic resistance and additional resistance according to the causes of resistance. Additional resistance also includes ramp additional resistance, curve additional resistance and tunnel additional resistance. According to the data, the basic resistance per unit weight of CRH3 EMU is as follows: w0 ¼ 8:63 + 0:07295  v + 0:00112  v2 ðN=tÞ

(6.13)

The formula for the additional resistance of the curve is: wr ¼ 600=R

(6.14)

The formula of tunnel additional resistance is: ws ¼ 0:00013Ls

(6.15)

6.2 CTCS-3I dynamic velocity curve algorithm

209

In eqs. (6.13) to (6.15), wr is curve resistance per unit weight (N/kN), R is curve radius (m), ws is tunnel additional resistance per unit weight (N/kN), Ls is tunnel length (m). When there is no temporary speed limit on the line, ATP curve is calculated from the opposite direction of the target point to the current allowable speed of the train, and then the speed remains unchanged until the current position of the train. The acceleration of emergency braking is larger than that of conventional braking, so the emergency braking distance is smaller than the conventional braking distance. Under the condition of a temporary speed limit, from high speed when the train down to a lower speed, still according to the circuit parameters, the performance data such as braking curve calculation, the brake of the target as the starting point of the temporary speed limit, the goal of the brake speed for the size of the temporary speed limit, receives the mobile authorization includes the target position and velocity, Then, the target distance is divided into N segments by using the piecewise iteration method discussed above, and the target velocity of the known target point is calculated in the opposite direction to the higher velocity. When calculating the initial velocity and position of each cell segment, it is necessary to obtain the maximum limited velocity at the current position and compare the current maximum limited velocity. If the current velocity is less than the maximum limited velocity, then calculate the acceleration at the current position and then calculate the initial velocity and position of the segment. If the current speed is greater than the maximum speed limit, the initial speed of the segment is equal to the maximum speed limit. This cycle continues until the train is located.

6.2.3.4 ATP speed protection model ATP protection curve is calculated by train traction based on braking performance and line conditions. Through the train safety braking curve, on-board ATP can monitor the running speed of the train in real time to ensure the safe operation of the train [11].In CTCS-3 train control system, ATP protection curve adopts target-distance mode, and the algorithm of target-distance mode curve is based on the calculation of safe braking distance of train. In the process of train braking, the speed is continuously changing, so the braking force of the train is constantly changing, that is, the acceleration of the train is also continuously changing, so the method of variable step length is used to calculate. Variable step size can be divided into variable time step size, variable distance step size and variable speed step size method. The braking acceleration of the train in the whole braking process can be expressed as: a ¼ 0:00981ðf + w + wi + wr + ws Þ

(6.16)

210

6. Shorten the tracking interval through the control algorithm

In Formula (6.16), f is train braking force (N/kN), w is train unit basic resistance (N/kN), wi is unit ramp additional resistance (N/kN), wr is unit curve additional resistance (N/kN), ws is unit tunnel additional resistance (N/kN). Because the wheelset, motor and other rotating objects will consume part of the kinetic energy, the rotational part of the kinetic energy consumption is generally calculated according to the proportion of the train function, the proportion value is called the rotational mass coefficient γ. In this way, the train braking acceleration is modified as: a¼

0:00981 ðf + w + wi + wr + ws Þ 1+r

(6.17)

According to the kinematics formula, it can be obtained that within Δt time, the speed increment Δvi of the train is: Δvi ¼

0:00981 ðf + w + wi + wr + ws ÞΔt 1+r

(6.18)

Vinitial is the initial braking speed of the train (m/s), Vfinal is the final braking speed of the train (m/s), and γ is the mass coefficient of rotation. Then, these displacement Δsi changes within Δt time are superimposed, and the train safety braking distance S can be obtained: S ¼ S 1 + S 2 + S3 + S 4

(6.19)

By connecting the Δsi and Δvi, VdS graph, namely ATP safety braking curve of target-distance mode, can be obtained. There is always some error in discrete calculation, but when enough hours are taken, the calculation error of train safety braking curve can be controlled within 0.5%, which can meet the engineering requirements. Since the train needs to apply maximum braking force during emergency braking, that is, the train applies air braking from the very beginning, the on-board ATP needs to consider the time of train traction disconnection and braking response, that is, the idle time, when calculating the emergency braking curve of the train. The braking distance of the train is the sum of the safe braking distance of the train and the empty running distance of the train, namely, the formula (6.20): S¼

n X

ΔSi ði ¼ 1, 2, 3, …, nÞ

(6.20)

i¼1

By connecting the Δsi and Δvi, VdS graph, namely ATP safety braking curve of target-distance mode, can be obtained. Since the train needs to apply maximum braking force during emergency braking, that is, the train applies air braking from the very beginning, the on-board ATP needs to consider the time of train traction disconnection and brake response, i.e., empty time, when calculating the emergency braking curve of the train [12].

6.2 CTCS-3I dynamic velocity curve algorithm

211

The braking distance of the train is the sum of the safe braking distance of the train and the empty running distance of the train, namely: Sbraking ¼

n X

ΔSi + vtempty ði ¼ 1, 2, 3, …, nÞ

(6.21)

In formula (6.21), v is the initial braking speed of the train (km/h), and tempty is the empty running time of the train. (1) Analysis of step selection of safety braking curve The train overspeed protection curve is calculated according to the step size and cannot be precisely calculated to the target value. An allowable error ξ is given in the design. When the train speed value falls within the error range, it equals that the train speed has met the target value vmax, which is the termination condition of iterative calculation. In the calculation of train safety braking distance, the step selection method can be divided into time step Δt, distance step ΔS and speed step ΔV. In the calculation process, the accuracy and convergence of the calculation results will be different if the step size of different parameters or the step length is different. (2) Variable step size Δt method In traction calculation, usually select Δt as the step size, and in order to improve the accuracy of the calculation result, adopt the variable step size method for calculation, the step size Δt is usually 50 ms to 1000 ms, the speed is relatively small at the beginning, the step size is large, and then with the increase of speed, the step size gradually decreases. If the train speed value crosses the allowable error interval in the cycle, the trial function is required to reduce the step size Δt so that the speed value can be captured. The defect of this method is that the calculation needs to be rolled back by trial and error, which is not good for simulation frame stability and time synchronization. However, in the fixed step method, the step length is often designed to be very small, such as 0.01 s, which seems accurate and does not need trial and error. However, in some stages of train operation, such as the initial stage of traction running with maximum traction force, a very small step is obviously unnecessary. Secondly, if the allowable error value is not properly obtained at this time, the train is running close to the lower limit of the allowable error. In fact, the train starts to prepare for braking before reaching the maximum value, which is not conducive to improving the operation efficiency. Therefore, in order to meet the requirements of necessary accuracy and efficiency, it is necessary to select an appropriate step length according to the speed of the train.

212

6. Shorten the tracking interval through the control algorithm

(3) Select different step size Δt, Δv, Δs method Taking the conventional braking of CRH3 EMU as an example, assuming that there is no slope, no tunnel and no curve, using simulation calculation, when the train is approaching the stop point, When v ¼ 7.2 km/h, a ¼ 0.6 m/s2; when the train is close to the braking point, when v ¼ 300 km/h, a ¼ 1.7 m/s2. When the selected time is step size, it is assumed that Δt ¼ 0.5 s. According to the kinematics formula: ΔV ¼ aΔt, ΔS ¼ (Vend  Vstart) /(2a), we can know: V ¼ 7.2 km/h, calculated ΔV ¼ 0.3 m/s, Δs ¼ 1.1 m. When V ¼ 300 km/h, ΔV ¼ 0.85 m/s, Δs ¼ 41.7 m. When the speed is selected as step size, it is assumed that ΔV ¼ 3 m/s, and according to the kinematics formula: Δt ¼ ΔV/A, ΔS ¼ (Vend2 – Vstart2)/(2a), it can be known that when V ¼ 7.2 km/h, it is Δt ¼ 5 s, Δs ¼ 17.5 m. When V ¼ 300 km/h, Δt ¼ 1.76 s, Δs ¼ 147.1 m. When the distance is selected as step size, it is assumed that ΔS ¼ 5 m, according to the kinematics formula: ΔV ¼ Vend  Vstart, Δt ¼ ΔV/a, it can be known that v ¼ 7.2 km/h, ΔV ¼ 3.16 m/s, Δt ¼ 5.27 s. By comparing the results of the three methods, it can be seen that the calculation accuracy of the method with time as step length is high near the parking point, but it is poor near the braking point. The method of selecting the speed as step has higher accuracy when the acceleration is large, but poor accuracy when the stop point is near. When the distance is the step size, the calculation accuracy is higher when the speed is larger. Considering in the process of train braking, acceleration is generally less than 2 m/s2, as if to choose delta v for step calculation accuracy is not too high, so as to select delta t as and delta s as traction calculation step length, as in when the train runs at low speed selected delta s for the step length, as to choose the train running at a high speed delta t as the step length, so that both can satisfy the requirement of the necessary precision, and can improve the convergence of function.

6.3 Optimization algorithm of CTCS-3I train movement authority Movement Authority (MA) refers to the section between the current position of the train and the obstacle in front (the furthest reached distance) and the line information contained in these sections, such as the static speed of the line, slope, temporary speed limit information, excessive phase information, etc., which is the driving certificate for the safe running of the train. From the point of view of railway signal, it is very important to shorten the tracking interval between trains by optimizing the moving authority.

213

6.3 Optimization algorithm of CTCS-3I train movement authority

6.3.1 Optimization algorithm of CTCS-3I train movement authority The moving authority is usually set at a certain distance in front of the train. Once set, it indicates that the train can safely run to this point, but not beyond this point. Moving block system guides the train to run safely on the line by continuously moving forward the target point of the train. Compared with CTCS-3 system, in CTCS-3I system, the RBC movement authority generation algorithm is the distance between the routes and trains. As shown in Fig. 6.8, RBC accurately locates the train on the internal topology according to the reported position of the train. According to the status of the train’s front approach and the constraint of the maximum MA length allowed by RBC, the longest idle approach in front of the train is allocated to the train, and the total length of these idle routes is calculated to generate MA.CTCS-3I generates MA from the rear end of the car in front. At the same time, MA contains the transponder, slope change point, speed change point, phase separation area, grade conversion area, RBC switching area and other information within the approach range assigned to the train in the static line description information, as well as the dynamic temporary speed limit information on the internal topology.

6.3.2 Dynamic control of train spacing based on real-time calibration of safety vehicle distance Train tracking interval control is the core technology of interval block system, and also the key to ensure safe and efficient train operation. At present the range of block systems including fixed block, quasi-moving Block and Moving block technique, etc., these techniques are for the fixed track interval, under the block systems, on the same route taken certain

MB-V Train2

MB-V0

Lr

LS1 Lr

FIG. 6.8

Train1

Train1

CTCS-3I system movement authority.

Lr

LS2

214

6. Shorten the tracking interval through the control algorithm

departure interval time of train group, on the basis of the same run offline optimal operation control curve, the train tracking interval and offline only actual optimal operation curve and departure intervals. To some extent, it restricts the improvement of high-speed railway network and line transport efficiency. Therefore a kind of real-time calibration based on the safety car is apart from the train interval dynamic control strategy is put forward, assuming more trains to run on the same route, the car is no longer dependent on offline optimal operation curve, but according to the running state of vehicles real-time adjust their operational control strategy, by optimizing the trace interval, improve the line transport capacity[13]. 6.3.2.1 Basic definitions (1) Definition of safe train distance. Safe train distance is the standard train distance to ensure safe and efficient following operation of high-speed train under normal circumstances. It is an important basis for behavior adjustment in the process of high-speed train tracking operation, and changes with the change of tracking operation[14]. (2) Off-line calculation of safe train distance. Off-line safety distance can be calculated by absolute braking and relative braking. The tracking operation mode under moving block includes absolute distance braking mode and relative distance braking mode. Absolute distance braking mode does not consider the speed of forward train, and the calculated end point of tracking train movement authorization is set as the position point of front car and rear car when braking starts. In the relative distance braking mode, not only the current position of the vehicle in front but also the speed of the vehicle in front should be considered. In other words, when tracking the braking of the train, the vehicle in front is still in the process of dynamic adjustment, and the vehicle behind needs to adjust the running state according to the real-time position and speed information of the vehicle in front and select the appropriate braking gear. The end point of tracking train movement authorization should be the front car and the rear car in operation. In the current train control system of high-speed railway, absolute distance braking mode is still selected to ensure the safety of train tracking operation. In this section, absolute distance braking mode is adopted to calculate the minimum safe tracking interval. As shown in Fig. 6.9, L2 is the distance tracked by the train within the driver’s reaction time, L3 is the common braking distance corresponding to the current speed of tracking train. ΔL is the safe stopping distance; L4 is the train length; L5 is the emergency braking distance of the vehicle ahead.

215

6.3 Optimization algorithm of CTCS-3I train movement authority Track train

Front train

Lmin

L2

FIG. 6.9

L3

ΔL

L4

L5

Absolute distance braking mode.

(3) Optimization of off-line safe train distance. Off-line optimal speed trajectory planning is the cornerstone of operation optimization, and train tracking control strategy and multivehicle cooperative optimization are deeply studied on this basis. By setting the selection mechanism and using the difference algorithm to solve, the offline optimization steps of train running speed track are as follows. Step 1: Initialize the basic parameters of high-speed train, interval line parameters (speed limit, slope, curvature and other characteristic parameters), differential evolution algorithm control parameters, and set the iteration algebra G ¼ 0. Step 2: Set cruise speed and initial braking speed as decision variables to initialize the population.
 yi,j G ¼ vi,j c , vi,j b (6.22) Type (6.22), yi,j G , j is the jth individual of train i in the G generation population, vi,j c , j is the cruising speed of the jth individual of train i, vi,j b , is the initial braking speed of the jth individual of train i. Step 3: According to the differential evolution algorithm, the G generation population individuals were mutated and crossed. Step 4: Construct the fitness function of individual evaluation, calculate the fitness function of contemporary population and crossover individuals, and make comparison, and select better individuals to enter the next generation of population iteration. Step 5: Determine whether the algorithm terminates. If so, end the optimization process, output the optimal solution set, and perform Step 6. Otherwise, return to Step 3 to continue optimization, with G ¼ G + 1. Step 6: Search the optimal solution set and output the optimal solution of on-time running time that meets the requirements of high-speed train schedule, that is, the trajectory curve of off-line optimal train running speed.

216

6. Shorten the tracking interval through the control algorithm

6.3.2.2 Train dynamic adjustment strategy (1) Dynamic train interval control. Train interval dynamic control means that the train collects running data in real time and monitors the actual tracking interval distance between adjacent trains in real time. Evaluate whether it meets the requirements of safe vehicle distance, analyze the actual tracking interval distance and safe vehicle distance of the tracking train, adjust its running conditions in real time, and recalculate the optimal speed mode curve. Tracking interval optimization, the principle of operation control strategy for dynamic adjustment mechanism is shown in Fig. 6.10, change, whether the running state of vehicles, must be based on the safety car distance from S and actual tracking intervals between trains S, combined with dynamic traffic information, adjust after the car’s running status, for the purpose of safe and efficient traffic, to adjust their behavior [6]. (2) Train dynamic adjustment steps. Step 1: Check the distance between the rear train and the front train at the current speed to determine whether the distance meets safety requirements. If s > S, go to Step 2; if s ¼ S, go to Step 3; if s < S, go to Step 4.

Determination of safety and efficiency conditions for train tracking interval

Real-time train tracking interval monitoring

Train running condition Information collection

Train running condition Train operation online adjustment mechanism

Train running condition Information collection

distance Adjusted train tracking operation control strategy The run data

Traini

The run data MA

MA

RBC FIG. 6.10

Dynamic train adjustment strategy.

Train1

6.3 Optimization algorithm of CTCS-3I train movement authority

217

Step 2: s > S, indicating that the steady-state following operation has changed. At this time, the rear vehicle speeds up to shorten the vehicle distance and make full use of the line transport capacity. The initial speed of the train’s behavior adjustment is the current speed of the car behind, and the final speed is the current speed of the car ahead. During the behavior adjustment process, the safety and efficiency of following motion are continuously detected. Go to Step 1, and judge the dynamic safety of car distance according to the current speed. Step 3: s ¼ S, then the behavior of the rear car is not adjusted and go to Step 1. Step 4: s < S, the rear car decelerates and stops at the current acceleration. During the deceleration and stop process, the safety of following motion is continuously detected, and whether the train meets the safety requirements is judged according to its current speed, and the behavior is adjusted according to the new situation [7]. (3) Real-time adjustment of curve generation. When multiple trains track running on the same line, RBC collects realtime information such as train operating conditions, running speed and position, and transmits it to on-board equipment of adjacent trains. Activate the interval distance monitoring module to calculate the minimum safe tracking distance corresponding to the actual tracking distance of the vehicle in front and the current speed; Determine whether the actual tracking distance meets the safety and efficiency standards through the decision module. Finally, the train state adjustment module is activated to adjust the running condition of the tracking train based on the principle of state transition to optimize the tracking interval. The adjustment of tracking train control strategy should be based on the following safety and efficiency constraints to ensure the safe and efficient operation of trains and improve the overall carrying capacity of high-speed railway lines. In order to ensure the safe operation of high-speed trains and avoid collisions, the actual tracking interval of adjacent trains should be strictly greater than the minimum safe tracking distance [8]. The safety constraint function of tracking process is denoted by Φ1, and the safety constraint condition should be Φ1 < 1 ϕ1 ¼

L min S

(6.23)

In Formula (6.23), S is the actual tracking interval between adjacent trains. Lmin is the minimum safe tracking interval. The running process of high-speed train is actually completed by the permutation combination and dynamic transformation of traction, cruising, idling and braking. In the course of train running, the cruising state is essentially a special state of traction condition in which traction force and resistance cancel each

218

6. Shorten the tracking interval through the control algorithm

other, so it is classified as the same condition as traction condition in the description of transformation principle. Under normal circumstances, due to the limitation of train traction drive system, the traction/cruising state can only be converted or converted into idle running condition, but not directly into braking condition, and the braking state is the same. However, unexpected events such as track breaking, obstacles in front and natural disasters may happen randomly. In accordance with the principle of safety first, braking measures need to be taken immediately. Therefore, the transition from traction condition to braking condition should be increased when and only when an emergency occurs. Idle state can be arbitrarily changed to traction, idle or braking conditions. In order to optimize the train tracking interval, it is set that when steps 1, 2 and 3 are respectively met, the train running state shall undergo the operating condition transition operation as shown in Fig. 6.11.Where, condition 1 is Φ1 > 1, that is, when the minimum safe tracking interval distance is greater than the actual tracking interval between adjacent trains, the train changes from traction condition to inert condition. Condition 2 is Φ1 < 1, that is, the minimum safe tracking interval distance is less than the actual tracking interval between adjacent trains, the train changes from inert working condition to traction working condition, and when the train encounters emergency stop, the train takes emergency braking measures. Condition 3 is Φ1 ¼ 1, that is, when the minimum safe tracking interval is equal to the actual tracking interval between adjacent trains, the train remains in the original state unchanged.

6.3.3 Algorithm for shortening locking delay based on vehicle–ground cooperation In railway operation, when already out into the road suddenly need to cancel, should be based on the close to locking of the interlock function to determine whether delay unlock to avoid the risk of aggressive train, when the function is applied to the high speed railway, however, will increase with the increase of train speed and close to the section length 3 Coasting

1 3

2 Traction

FIG. 6.11

1

3

2 Bracking

Conversion diagram of train operating conditions.

6.3 Optimization algorithm of CTCS-3I train movement authority

219

X3

P1

P2

X X1

Station approach section

FIG. 6.12

Departure route

Schematic diagram of close lock.

New Movement authority

FIG. 6.13

Receiving route

Old Movement authority

Schematic diagram of canceling the route and shortening the locking delay.

and increase the delay time close to locking, affect the traffic efficiency, shown in Fig. 6.12 as follows. Fig. 6.13 shows how to shorten the locking delay through vehicle– ground cooperation. If CBI can determine whether the approaching train can stop safely before the position of the signal, it can determine whether the approach can be unlocked immediately, without setting the delay of approaching section and unlocking. In this way, the operation efficiency can be improved without relying on occupying detection equipment [7].

6.3.3.1 Vehicle–ground cooperation scheme To realize the vehicle–ground cooperation function, the first step is to determine whether the train can stop, the ground informs the train of the new stopping point, and the train calculates the required stopping distance according to its current speed, position and other information, judges whether it can stop safely and reports the result to the ground. The specific realization process includes: according to the conditions of train operation and RBC weight transfer, CBI first asks RBC, RBC then asks on-board ATP, and then on-board ATP reports the results to RBC. The RBC finally notifies the CBI to perform the operation. The scheme includes four cases: non-opt-in car-to-ground cooperation under normal circumstances, opt-in car-to-ground cooperation under normal circumstances, opt-in non-opt-in car-to-ground cooperation under abnormal circumstances, opt-in car-to-ground cooperation under abnormal circumstances[15].

220

6. Shorten the tracking interval through the control algorithm

1. Under normal circumstances, nonownership vehicle–ground cooperation scheme Figure 6.14 shows the vehicle–ground cooperation scheme in normal situations. (1) When a train’s MA includes an approach, RBC shall notify CBI that “the approach is locked.” (2) If CBI wants to unlock a certain path, but the path has not been locked by MA, it will be unlocked directly; If it has been locked, an unlock request is made to the RBC. (3) RBC sends a new MA to on-board ATP according to the unlocking request, asking whether it can park in front of the new MA endpoint. (4) The train calculates parameters such as its own speed and distance from the new terminal to determine whether to accept the new MA, and reports the result to RBC. (5) RBC’s notice to CBI may be canceled if the train report accepts a new permit, otherwise the notice to CBI cannot be canceled. (6) If CBI receives cancellation permission, directly unlock the access, otherwise keep the access locked.

2. Cooperation scheme of vehicle and ground under normal circumstances In the option delivery condition, compared with the nonoption delivery condition, there is an interaction process between the receiving RBC and the handing RBC: After the CBI sends a “request for unlocking” to the receiving RBC, the receiving RBC needs to use message M224 to ask the transferring RBC whether it can determine to shorten the Route Related Information (RRI) it sent previously to the new endpoint. The handover RBC interacts with the vehicle-borne ATP using messages M9 and M137/M138 according to the new endpoint specified by M224 in the same way as the nonhandover process to determine whether it can stop. If parking is possible, the receiving RBC is told “parking is possible” by message M206 (in which the determination status is set to “yes”), and then the receiving RBC informs CBI that it agrees to its unlocking request. CBI can unlock immediately without delay. If the stop is not possible, the handing RBC notifies the receiving RBC of “unable to stop” with message M206 (where the determination status is set to “uncertain”), the receiving RBC accordingly rejects the CBI request, and the CBI will no longer unlock the path. Cooperative Shortening Movement Authority (CSMA) under the condition of handover, as shown in Fig. 6.15, where M224 represents the “request route related information confirmation” message sent by the receiving RBC to the handover RBC in the handover process. M206

221

6.3 Optimization algorithm of CTCS-3I train movement authority

RBC

ATP

CBI Request to unlock the route

Request to shorten MAM9 The train can The stop train can not stop

The train can stop

Agreed to shorten

Agree on requirement

MAM137

Refused to shorten The train can not stop

FIG. 6.14

Refuse the request

MAM138

CSMA in nonweighted condition.

Receive RBC

Transfer RBC

ATP

Request confirmation Whether to shorten the MA

Request to shorten

CBI Request to unlock the route

M224

MAM9 The train can stop The train can't stop

The train can't stop

FIG. 6.15

The train can stop

Agreed to shorten MAM137

Refused to shorten MAM138

CSMA at alternating weights.

Certain shorten

M206

Agree on requirement

Uncertain shortening M206

Refuse the request

222

6. Shorten the tracking interval through the control algorithm

TABLE 6.4 Message meanings. Message name

Message means

Message name

Message means

MAM9

Request permission to shorten the journey

M224

Ask to confirm if it can shorten the MA

MAM137

Agree to shorten MA

M206

Make sure it can/can’t shorten MA

MAM138

Reject to shorten MA

indicates the Route related information confirmation message sent by the transferring RBC to the receiving RBC during the assignment. Table 6.4 describes the specific message meanings.

6.4 Vehicle–ground cooperation scheme in abnormal scenarios During the process of vehicle–ground cooperation, other emergency conditions, such as shortening the movement authority and unconditional emergency stop, should be activated to ensure the safety of train operation. As shown in Fig. 6.14, under the condition of the power, if RBC send new mobile after authorization in original mobile activate the emergency braking conditions within the scope of authority, the RBC shall immediately send new MA to the on-board ATP (endpoint to activate the emergency brake and the car closer collaboration end distance train), at the same time send the CBI “refused to unlock” message, end the vehicle–ground collaboration process.

6.5 Vehicle–ground cooperation scheme in abnormal scenarios Under the option delivery condition, after the transfer RBC sends the MA, the emergency braking condition is activated within the jurisdiction of the original MA, and the emergency braking condition is sent to the on-board ATP in the manner not under the option delivery condition. At the same time, the MA sent to the receiving RBC cannot be determined, and the receiving RBC sends the “refuse to unlock” message to the CBI. Receiving RBC will not send any route information under normal conditions before receiving M206. If the shortened MA condition is activated within the RRI range during this period, a new access information RRI shall be immediately sent to the handover RBC and a “unlock denied” message sent to the CBI. After receiving the new route information,

References

223

RBC will exit the CSMA process and send the new MA to the train based on the new route information. Through the provisions of the above abnormal scenarios, the risks in the operation of the CSMA scheme are prevented, and the safety of driving is further guaranteed.

References [1] China Railway Corporation, CTCS-3 Train Control System System Requirements Specification (SRS). [2] China Railway Corporation, CTCS-3 Train Control System Functional Requirements Specification (FRS). [3] J.F. Wang, A Moving Block Train Control Method and System Based on CTCS-3, China, S20191219, Intellectual Property Publishing House, 2021. [4] D.X. Zhao, J.F. Cheng, L. Yue, C. Liu, A study on the train control system for low density operation on Qinghai-Tibet, Railway Transp. Econ. 42 (05) (2020) 59–64. [5] L.J. Shi, J. Wang, Reliability analysis on the train control system in the CTCS-3 operating mode, Smart Resilient Transp. 3 (1) (2021) 25–36. [6] Y.C. Tong, P. Zhao, J.C. Zhang, W.B. Song, Research on single-track railway capacity expansion scheme based on moving block, Railw. Transp. Econ. 42 (2) (2020). 16–21+61. [7] Z.J. Li, B.H. Mao, Y. Bai, et al., Integrated optimization of train stop planning and scheduling on metro lines with express/local mode, IEEE Access 7 (88) (2019) 534–546. [8] Z.J. Li, B.H. Mao, M. Su, et al., Optimal design of safe braking curve of on-board ATP system in high-speed train, J. China Railw. Soc. 40 (4) (2018) 18–23. [9] W.Z. Huang, X.S. Ji, L. Liu, K.C. Li, D.H. Niu, Key technology of high speed adaptability of CTCS-3 level train control vehicle equipment, China Railw. Sci. 31 (03) (2010) 87–92. [10] N. Besˇinovic, E. Quaglietta, R.M.P. Goverde, A simulation-based optimization approach for the calibration of dynamic train speed profiles, J. Rail Transp. Plann. Manag. 3 (4) (2013) 126–136. [11] B. Zhang, S.J. You, L.F. Zhang, D.M. Li, Y.L. Cheng, Energy-efficient speed profile optimization for high-speed railway considering neutral sections, IEEE Access 9 (25) (2021) 90–100. [12] W. Shangguan, R. Luo, H.Y. Song, et al., High-speed train platoon dynamic interval optimization based on resilience adjustment strategy, IEEE Trans. Intell. Transp. Syst. 23 (5) (2022) 4402–4414. [13] D. Pan, Y.P. Zheng, Dynamic control of train interval based on real-time calibration of safe headway, J. Traffic Transp. Eng. 14 (1) (2014) 112–118. [14] D. Pan, M. Mei, Y.P. Zheng, Interactive evolution between safe headway and control strategy of high-speed trains during following operation, J. Traffic Transp. Eng. 14 (5) (2014) 90–100. [15] Q.H. Li, Research on vehicle-vehicle collaboration shortening mobile authority scheme, Control Inform. Technol. 6 (2020) 83–89.

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C H A P T E R

7 Novel methods for improving transport capacity 7.1 Train-to-train communication 7.1.1 Overview of train-to-train communication In the existing train control system, train control is realized by the way of ground-train or train-ground communication. Train-to-Train (T2T) communication changes the communication mode of traditional train control system and opens up the channel of direct communication between trains. Trains can obtain the location, speed, and other information of adjacent trains in real time. The train control system using T2T communication technology has more simplified wayside equipment and signal system structure, and the interaction between equipment can be more efficient and direct. The control command of the train control system based on T2T communication is directly generated by the train itself, which is more real-time than the traditional CBTC system. In recent years, many researches on train-to-train communication and train control system based on T2T communication have been carried out. The main research contents include improving wireless communication transmission performance and channel capacity, and network communication architecture serving railway transportation [1]; reliability, availability, security, and maintainability of vehicle-vehicle communication; train control system based on vehicle communication, such as VBTC and TcCBTC; multitrain virtual grouping, cooperative control, and moving block technology based on vehicle-vehicle communication. Table 7.1 lists some of the latest research achievements of train control systems based on vehicle-vehicle communication. T2T communication is the key technology of the next generation train control. The train control system based on T2T communication is the main research content at present, such as Urbalis Fluence system and TACS

Theory and Technology for Improving High-Speed Railway Transportation Capacity https://doi.org/10.1016/B978-0-323-99700-3.00004-9

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Copyright © 2023 Elsevier Inc. All rights reserved.

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7. Novel methods for improving transport capacity

TABLE 7.1 Train control system based on T2T communication. Research contents

Characteristics

Moving blocking

Using vehicle-vehicle communication to achieve moving block

Train control system based on T2T communication

TACS, train-centric, etc.

Virtual coupling

Virtual mechanical linkage

Coordinated train control

Multitrain cooperative operation

system, etc. [2,3]. T2T communication can realize train centralization in train operation control and on-board equipment can complete movement authority (MA) calculation, overspeed protection, interlocking, and other functions. Equipment such as balise and track circuit should be canceled to reduce the investment in construction and maintenance and improve the maintenance efficiency of signal system [4,5]. Using T2T communication technology, Train Autonomous Circumambulation System (TACS) realizes independent management. Control commands are directly generated by the train itself to shorten control links and reduce communication delay. Improve transportation efficiency. In June 2020, the TACS system of Qingdao Rail Transit Line 6 completed the function verification. Shenzhen Rail Transit line 20, which uses TACS system, is under construction and will operationalize in 2021. Shanghai Rail Transit Line 3 is undergoing renovation, with the original CBTC system being upgraded to TACS system. Coordinated train control that is a train operation control technology achieves optimization goal by coordinating multiple trains. T2T is the premise of it. Coordinated train control can be used to solve the problems of delayed propagation and energy saving to improve the performance of rail transit system, which endows the train with greater autonomy, enabling the train to actively perceive the operating environment formed by the requirements of the surrounding trains and the operation diagram of the train, and trains can actively communicate with each other to determine their respective mobility authorization [6]. Virtual coupling is a signal technology that realizes the virtual mechanical linkage of multiple trains based on T2T communication. It can dynamically connect multiple trains in a train fleet to greatly reduce the distance between trains and increase line capacity. European Shift2Rail plan devote to realize virtual coupling. Clive Roberts, the professor of the University of Birmingham, is carrying out a research project called Performing Rail, using holistic system approach to solve the safety problem and performance loss of virtual coupling caused. Beijing Jiaotong University is also conducting research on virtual coupling, including optimized train control, collision prevention, and overspeed protection [7–9].

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7.1 Train-to-train communication

7.1.2 Train control system based on T2T communication 7.1.2.1 Train-centric CBTC system Train-centric CBTC System (TcCBTC) is a train-centered train control system using T2T communication technology. Fig. 7.1 shows the basic structure and information control flow of TcCBTC [10]. Train control system based on T2T communication is still composed of vehicle on-board controller (VOBC) and wayside equipment. Wayside equipment includes automatic train supervision (ATS), train management module (TMM), object control unit (OCU), wayside signal infrastructure equipment (signal, switch, etc.). ATS monitors the running status of trains, sends timetable to trains, and protects trains from faults when on-board devices fail. TMM takes part of the safety functions of Zone Controller(ZC) and execute train registration and cancelation, train information storage and forwarding, etc. It does not have complex control calculation logic. OCU obtain the status of basic signal equipment such as signal machines and switches and control them. On-board equipment is composed by digital map module, on-board interlocking module and train control module. Digital map module acquires train location acquisition and route planning by using a variety of train location technologies. Interlocking module inherits all the functions of traditional interlocking and achieves higher automation degree such as automatic route handling and automatic reentry. Train Drive commands Status Drive commands

Traffic Plan

Interlock Logic

ATS

OCU Status

Traffic Data

TMM Train Info

Train

Traffic registration

Real-time Communication with Train Location

TMM onboard

Digital Map

Forward train location

Moving Authority ATP Module

Onboard FIG. 7.1

TcCBTC structure.

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7. Novel methods for improving transport capacity

control module includes three basic functions: train management, movement authority (MA)and train speed control. The workflow is: (1) ATS sends the timetable to train and the train applies for registration with the TMM. If the login conditions are met, TMM allows the train to log in; (2) TMM captures and stores the status information of all trains and sends them to each train running; (3) Based on messages from TMM, the train autonomously judges the communication train ahead; (4) The train communicates with the train ahead to obtain the position and speed information; (5) The train obtains the OCU message and analyzes the status of the forward signal. (6) On-board ATP calculates MA according to the end of the route, the line, and the position of the train ahead; (7) The train generates a speed profile to control the speed of the train. As the controller of the wayside equipment, OCU receives control commands from the VOBC and ATS. Normally, the VOBC sends control commands to the OCU based on the on-board interlocking, when the VOBC fails or the communication between the VOBC and ATS is interrupted, the ATS sends a control command to the OCU based on the back-up interlocking to ensure the safety of train operation. The OCU sends status information to the VOBC and ATS. The ATS sends the timetable to the VOBC, and the VOBC sends the train location, speed, and fault alarm information to the ATS. Fig. 7.2 shows the scenario in which train B that installed TcCBTC runs autonomously [11]. The VOBC of train B obtain information provided by other trains and OCUs using wireless communication technology. According to the information received, train B will actively calculate its own MA, while sending control commands to OCU to turn the switch into the correct position. Compared with the traditional CBTC train which B

C 5G-D

5G-E

1DG

7G

OCU OCU 4DG

A

1

OCU 14G

4

6 D

OCU 2

FIG. 7.2 Working scenario of train.

OCU

8DG 8

16G

229

7.1 Train-to-train communication

passively receives the moving authorization, the train in TcCBTC can actively calculate its own moving authorization and actively control the switch ahead, which has more autonomy.

7.1.2.2 TACS TcCBTC is a train control system with the main characteristics of the next generation train control system, such as autonomous train operation mode and train centralization. TACS system is a typical autonomous train operation control system that adopts T2T communication [12]. Fig. 7.3 shows the system structure. Trains communicate with each other using LTE wireless networks. The control center is equipped with an ATS server, a dispatcher workstation, and a screen. The control center receives the information of the train position and trackside equipment such as switches and signals, and transmits the timetable to the train. Through the data communication network(DCS), the train receives the timetable and implements independent control operation, independent overspeed protection and independent route setting according to the actual running status.

Dispatcher Object Controller

Control Center Screen

State of train and equipment

Control command

BackBone network

Position, Speed

Timetable LTE

VOBC DMI

FIG. 7.3

Structure of TACS.

VOBC

ATS Server

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7. Novel methods for improving transport capacity

TACS has many advantages. The simplified system reduces the type and quantity of equipment, reduces the construction and maintenance workload, and reduces the investment cost of the whole life cycle. Interlocking and MA calculation executed by on-board equipment independently, failure cannot lead to the risk of regional degradation. In terms of improving transport capacity, T2T communication is timeliness, low latency, and more reasonable control logic, which is conducive to improving the overall efficiency of the transportation system. 7.1.2.3 Urbalis Fluence Urbalis Fluence is Alstom’s CBTC extension solution for the Lille metro in France, as shown in Fig. 7.4. Urbalis Fluence uses intelligent on-board equipment and direct communication between trains, reducing communication response time, communication interface and maintenance costs. The time headway is reduced by 60 s compared with the traditional CBTC system. This performance can be achieved by shortening the response time through direct communication between trains and optimizing the locking mode of train track resources in key sections. Technical highlights of Urbalis Fluence adopted by Lille Metro include unmanned and unattended train operation, train control system based on moving block principle and centralized traffic control system [13,14].

7.1.3 Improving capacity by T2T (1) Reduce communication link CBTC system consists of automatic train supervision (ATS), automatic train operation (ATO), automatic train protection (ATP), zone controller

FIG. 7.4 The structure of Urbalis Fluence.

231

7.1 Train-to-train communication

service braking emergency braking

AP1

AP2

APn ……

Backbone network

ATS

FIG. 7.5

Zone Controller

Communication based train control system.

(ZC) and information access point (AP). Fig. 7.5 shows the basic structure of the CBTC system [15]. The ATS subsystem makes a timetable for each train. The train sends the train number, location and speed information to ZC. ZC centrally receives the information of all trains in the area under its control, calculates the MA of each train according to line conditions, train positions and obstacle information, and then sends it to the train through wireless communication. ATO subsystem calculates the optimized operation curve according to the travel time and other performance indicators (such as energy saving and passenger comfort, etc.) given by ATS. The ATP subsystem calculates the safe braking curve based on the latest received MA. Once the train overspeeds, the ATP subsystem will initiate the service or emergency braking before the ATO subsystem, to protect the train from overrunning the MA. Different from traditional vehicle-ground communication, in the train control system of vehicle-vehicle communication, the train acts not only as the terminal communication point, but also as the relay station of other trains, as shown in Fig. 7.6 [11]. When all AP work normally, cooperative relay is used to enhance the communication between AP and SA. In the event of an access point failure, the train in front can use T2T communication to report its location directly to the train behind it. In the train control system based on T2T communication, trains communicate directly with neighboring trains. Compared with the traditional CBTC system, the control link between trains is shortened and communication time is reduced. The vehicleon-board equipment calculates the moving authorization and controls the train operation according to the state information and line conditions of the train ahead. Compared with

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7. Novel methods for improving transport capacity

Zone Controller

AP

AP …………

…………

…………

FIG. 7.6 T2T information transmission network.

traditional CBTC system, train control system based on vehicle-vehicle communication requires less time to update movement authorization, smaller tracking interval between trains and higher speed control accuracy [16,17]. (2) Autonomous handling route Fig. 7.7 shows a typical turn-back station. After using T2T communication, the station does not need to set up signal machines for protection, so X2, X3, X4, and other signal machines do not exist in the station using T2T communication technology. Point A and point B is the end of protective section, the P2, P4, P6, P8, P10, and P12 is switches. POE is train interference point in CBTC system, if the station equipment unavailable, the train must stop before POE. On-board interlocking can realize fine management of resources and direct train control [18]. (1) After the train clears the switch P2, the rear train can apply for the P2, shortening the arrival tracking time interval. X2

X1 POE

P2

X6 P12

P6

A

X10

X12

Station P8 X8

FIG. 7.7 Turn-back station.

P10

B

X4 P4

X3

7.2 Cooperative control

233

(2) When the train enters the turnback line and stops, traditional interlocking requires the driver to handle the exit turn back approach only after the end change is completed, and P8 switch is transformed. For on-board interlocking, the train can immediately apply for the resources of P8 switch again after clearing out P8 switch, and control switch from reverse to positioning, shortening the running time of train out and turn back. (3) In the process of turn-back, after the turn-back clears the P8 switch, the following train can immediately apply for the resources of P8 switch, shortening the running time of the train entering the turn-back line.

7.2 Cooperative control With the improvement of train operation density of high-speed railway, the disadvantages of high-density train operation are gradually revealed. That is, when the train is affected by the internal mechanical failure of the system, the external environment, the operation organization and management of high-speed railway and the interaction between trains, it is inevitable that the train will be delayed, and the delay will spread rapidly on the line, which will affect the subsequent trains in a short time. The delay time is the difference between the actual arrival time and the planned arrival time. Excessive delay will affect the punctuality rate of the train and is not conducive to the improvement of carrying capacity. The expression of train delay is that the tracking interval of the train will be unbalanced. Cooperative control between trains is a train operation control method to achieve optimization objectives by coordinating the operation control process of multiple trains in the system. It can not only solve the problems of delay propagation and energy saving, but also improve the capacity of bottleneck sections and ensure the operation efficiency of trains in busy main lines [19]. Cooperative control helps to reduce the train travel time and increase the number of running trains, so as to improve the line capacity.

7.2.1 Overview of cooperative control Cooperative control is an important research content of multiagent system. In multiagent system, the research content of cooperative control can be divided into two directions: one is to study the phenomenon of biological clustering in nature; The other is the research on how to coordinate the behavior of multiagent to cooperate in a similar mode. The latter is to study how multiple individuals with autonomy and rationalism

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7. Novel methods for improving transport capacity

distributed in the system determine how to control their behavior through cooperation in order to achieve a certain goal and task, that is, how to design control strategies to achieve control goals [20]. The basic idea of collaborative control is to produce additional energy, value and effect through the cooperation of multiple autonomous and rational individuals in the system. Based on this idea, train cooperative control studies how to design a train operation control method for multiple trains to improve single or multiple performance indexes of rail transit system under the condition of moving block and train-to-train communication. Multitrain cooperative control is a train operation control optimization method that aims to achieve global optimization, comprehensively considers the dynamic relationship between multiple trains, and improves the performance of rail transit system by adjusting speed and tracking distance between previous and following trains [21]. 7.2.1.1 Modeling analysis method and research content of train cooperative control Train operation control model is an important tool to study the method of train cooperative control. The research on train operation control model has always been an important part of train operation control. The existing train operation control models can be divided into three categories: models based on classical mathematics, “Top-Down” models and “Down-Top” models. (1) Classical mathematical model Train operation control is a complex process, which involves locomotive, vehicle, line, communication, signal and so on. Limited by the level of scientific development, the original train operation control model did not pay attention to the whole process of train operation control, but focused on a part of the train operation control process, such as braking process, traction process, interval operation, and so on. With the deepening of research, train braking model and train traction model have appeared successively, but the research on the whole process of train operation needs to be further studied. (2) “Top-Down” models The “Top-Down” model is based on system structure analytic hierarchy process. With the development of computer and control technology, the train operation control structure has gradually developed into hierarchical centralized control. This structure provides convenience for the application of “Top-Down” modeling method. From the perspective of equipment, train operation control can generally be divided into three levels, as shown in Fig. 7.8. The bottom layer is on-board equipment, including on-board safety computer,

235

7.2 Cooperative control

Control center

The top layer Station control center

Station control center

Station control center

trackside equipment trackside equipment trackside equipment trackside equipment The second layer The bottom layer Train 2 on-board equipment

FIG. 7.8

Train 1 on-board equipment

Schematic diagram of hierarchical centralized control.

human-machine interface, etc. The second layer is composed of trackside equipment, including track circuit, trackside electronic unit, balise, etc. The top layer is the control center, which realizes the optimal management and decision support of dispatching command. From the perspective of dispatching, the secondary management mode from the dispatching center (dispatcher) to the station (station attendant) and then to the train (driver) has gradually formed. Based on the hierarchical centralized control structure, many scholars have established the train operation control model from macro to micro “Top-Down.” Some models are used to study some subsystems involved in the train operation control process, such as communication system, interlocking, signal blocking system and train overspeed protection system. Other models are used to analyze the whole process of train operation control. A typical example is RailSim, which is commonly used in North American railways. It can calculate the operation time of the train, evaluate the traction performance of the locomotive, analyze the train operation process under different line conditions, calculate the start and braking of the train on the long slope, as well as the maximum traction weight and operation speed of the train according to the line section and train formation. UTRAS system is a general railway simulation system developed by Japan traffic control laboratory, which was applied in the s of last century. The system can carry out train operation calculation, delay recovery analysis, impact analysis of different communication signal systems, and evaluation of train operation capacity and effect. The “Top-Down” train operation control model is no longer limited to a certain part of the train operation control process, but began to pay attention to the analysis of the whole process of train operation control.

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7. Novel methods for improving transport capacity

(3) “Down-Top” models The “Down-Top” modeling method focuses on the description of interaction rules between individuals, and describes the whole system by establishing local or individual models and their relationships. There are many “Down-Top” modeling methods, such as cellular automata model, agent-based modeling and so on. Agent-based modeling is a typical “Down-Top” modeling method, also known as individual based modeling. It is a computing platform. On this platform, discrete autonomous units or agents detect the surrounding local information at each discrete time step, and then take corresponding actions according to a set of logical rules. The main research contents of train cooperative control are shown in Fig. 7.9. 7.2.1.2 Characteristics of train cooperative control (1) The train has greater autonomy. The train changes from passively waiting for the “train movement” instruction from the control center to actively sensing the operation environment composed of the surrounding trains and the requirements of the train diagram for the train. The train can actively communicate and communicate with each other to determine their movement priority and authority, and control the corresponding route and switch through interlocking. For example, in the Victoria line signal transformation project of London metro, the new automatic train operation system (ATO) gives greater power to local control and no longer relies solely on the control center [20]. (2) The boundary between train dispatching and signal system becomes blurred. Traditionally, the boundary between train dispatching and train operation control system is very clear. This hierarchical structure not only facilitates system management, but also restricts the further improvement of system efficiency. In order to further improve the efficiency, train cooperative control will improve the accuracy of train operation control, that is, accurately control the train to reach a certain position at a certain speed at a certain time. The control strategy given by cooperative control is a solution that includes three kinds of information: train speed, position and time, and emphasizes the accuracy of train speed, position and specified time. Swiss Federal Railway has developed a rail transit management system based on the integrated structure of real-time dispatching and train control to solve the cooperative traffic management in the bottleneck area. The method adopted by the system is to send real-time updated operation information including time, speed and route information to each train. The test shows that by providing relevant information through an intelligent human-machine interface, the system can control the

For dense stop queues, coordinating the starting sequence and time of multiple trains to reduce the peak power supply can reduce the cost of infrastructure such as power supply equipment.

Cooperative control aiming at reducing peak power demand reduction——PDR-oriented

1. Based on regenerativebraking technology 2. Based on regenerative braking + energy storage device 3. Use advisory_speed

Cooperative control aiming at energy saving——ES-oriented

Train cooperative control

Coordinate the operation process of multiple trains in the network, realize equal interval operation, minimize the average passenger waiting time and improve passenger satisfaction.

Interval control aiming at reducing average passenger wait time ——APWTR-oriented

Coordinate multiple train operation processes in the network, optimize train operation curve, avoid track occupation conflict and reduce average train delay time.

Real time train graphadjustment aiming at reducing average train delay reduction——ATDR-oriented Automatically judge the optimization objectives based on the operation environment, coordinate the train operation process in the network, and realize the corresponding optimization objectives.

Real time train graphadjustment for automatic adjustment of optimization objectives——AOO-oriented

FIG. 7.9 Research on train cooperative control.

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7. Novel methods for improving transport capacity

accuracy of train speed position corresponding to the specified time within
15 s [20]. (3) Real time performance of control algorithm. In order to realize the accurate management of train speed, position and time, the train cooperative control must meet the real-time requirements. Because the state of rail transit system changes from time to time, if it cannot meet the real-time performance, it will not be able to achieve the purpose of optimal control. Adopting cooperative control does not mean abandoning centralized control. Centralized control is changed to play the role of higher-level supervisor and standby system. While transferring more control rights to the cooperative system, it has relative priority. When its intervention is required under specific circumstances, it will take over the management of the system. The train graph under centralized control is still the execution basis for train departure and arrival. The train leaves the station according to the departure time specified in the train graph, and the arrival time specified in the train graph is an important reference for train operation. However, train dispatching and train operation control will be further integrated to control the train operation process more accurately through the integration of train diagram information and train operation control information.

7.2.2 Improve punctuality through train-train cooperation [20] In the high-speed railway equipped with advanced train control system, train to train or train to ground communication technology enables the train to follow the moving train at a constant tracking interval. Because the train may be affected by unexpected interference during operation, such as bad extreme weather, driving behavior of different drivers and infrastructure failure, these will lead to irregular train tracking interval, deviation from timetable and reduction of line capacity [22]. In urban rail transit, due to the short distance between stations, the adjustment of train tracking interval is usually carried out at the station (by detaining and skipping the train). For high-speed railway, the distance between high-speed railway stations is not only much longer than urban rail transit, but also there are often two different cities between stations. The method of train detain and skip stop is difficult to apply, so a new method of dynamically adjusting the train tracking interval is needed. 7.2.2.1 Train operation mode under cooperative control In the railway system, the train control module and traction/braking motor are usually separated, in which the train speed controller outputs traction/braking acceleration u. Then, the traction/braking motor

239

7.2 Cooperative control

transmits the acceleration command to the traction/braking force F based on the train mass. The research on cooperative control focuses on the train control module, as shown in Fig. 7.10. The train control module mainly has two control modes: one is automatic speed control by equipment, such as ATO; The other is manual driving by the driver. Due to the high real-time requirements of train cooperative control, equipment control has the characteristics of faster response than manual control. The train under cooperative control adopts ATO mode to control the train. ATO system consists of two levels of control behavior: high level control is used to calculate and update the optimal trajectory, and low level control is used to track the target speed and feedback. Based on ATO, a cooperation layer for coordinating train control can be established, as shown in Fig. 7.11. Resistances f

Train speed controller

t vˆ vlim v, x

Automatic speed controller(or driver)

x : position

Traction&braking motors

F+ Train

B

v, x

−

Speed sensors/ positioning devices

u : control commend

v : speed

f : resistances

t : time vˆ : recommended speed vlim: speed limit

FIG. 7.10

u

F + : traction forces B −: braking forces

Diagram of railway train control model.

Cooperative Control of Trains

High-level Control

High-level Control

High-level Control

Target Speed

Target Speed

Target Speed

Low-level Control

Low-level Control

Low-level Control

Train Speed Position

FIG. 7.11

Train Control Speed Commands Position

Train Control Speed Commands Position

Cooperative control in a higher level for ATO.

Control Commands

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7. Novel methods for improving transport capacity

7.2.2.2 Cooperative control of two trains to reduce delay time When the front train is delayed at the station, the first tracking train will be affected. After the front train leaves the platform, it is hoped that the tracking train will enter the station as soon as possible to reduce the delay of subsequent trains. Once the front train starts, the time when it leaves the platform area can be predicted. Therefore, the arrival speed (V(t0)) and arrival position (P(t0)) of the tracking train can be determined by transmitting information including time, speed and position to the tracking train, so as to guide it to stop at the shortest arrival time and reduce the impact of the front train delay on the tracking train. In case of departure delay of train i, the whole process starts from train i to the stopping train i + 1 includes two stages: Stage 1, time of train i leaving the station; Stage 2, time from train i + 1 entering the station to stop. The following formula is based on the assumptions: the block system is moving block; The acceleration process of the train is uniform acceleration; The train braking process is uniform deceleration. (1) Time of train i leaving the station There may be two situations in the process of train i from starting to completely leaving the station area, as shown in Fig. 7.12: ① When the distance taken by train i to accelerate to the station speed limit is less than the train length, the operation process of train i is: acceleration ! constant speed ! acceleration. At this time, the departure time (t_leaving) of train i is: t_leaving ¼

Train_length Limitspeed_station + Limitspeed_station 2  max _a

Speed Line speed limit

Platform speed limit

Platform Station_Pos

FIG. 7.12

The departure process of train i.

Position

(7.1)

241

7.2 Cooperative control

② When the distance taken by train i to accelerate to the station speed limit is greater than or equal to the train length, train i will accelerate out of the station uniformly. At this time, the departure time (t_leaving) of train i is: pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2  max _a  Train_length t_leaving ¼ max _a

(7.2)

where Train_length is the length of train i, m; Limitspeed_station is the station speed limit, m/s; max_a is the maximum acceleration, m/s2. (2) Arrival time of train i + 1 According to the relationship between station length (Station_length) and the distance required for train i + 1 to decelerate from the station speed limit to stop, the process of train i + 1 from start to complete departure from the station area can be divided into the following two cases: station^2 Case 1: When Station_length < Limitspeed , there may be two kinds 2 max b of train i + 1 entering the station, as shown in Fig. 7.13. (P(t0 ),V(t0 )) is the terminating position of train acceleration (existing under special conditions):

(1) Process 1: (acceleration +) uniform speed + braking (① in Fig. 7.13), where V(t0 ) is equal to Limitspeed_line, and t_runin used by train i + 1 to enter the station is: t_runin ¼

Limitspeed_line  V ðt0Þ P1  P ðt 0 Þ + max _a Limitspeed_line Limitspeed_line + max _b

(7.3)

where P1 ¼ Station_pos 

Limitspeed_line^2 2 max _b

Pðt0 Þ ¼ Station_pos  Station_length  Ls  +

Limitspeed_line2  V ðt0Þ2 2 max _a

V ðt0Þ2 2 max _b

In formula (7.3), V(t0) is the speed of train i + 1 at time t (i.e., the arrival speed), P(t0) is the position of train i + 1 at time t (i.e., the arrival position), Station_pos is the station position, Station_length is the station length, max_b is the train deceleration, Ls is the safe distance.

242

7. Novel methods for improving transport capacity

(2) Process 2: acceleration + braking (② in Fig. 7.13). At this point, t_runin used by train i + 1 to enter the station is: V ðt 0 Þ ¼

qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2 max _bðStation_pos  P ðt 0 ÞÞ

t_runin ¼ where 0

Pð t Þ ¼

V ðt 0 Þ  V ðt0Þ V ðt 0 Þ + max _a max _b

(7.4)

!   max _b V ðt0Þ2 max _b Station_pos  Pðt0Þ + = 1+ max _a max _a 2 max _a

Limitspeed station^2

Case 2: When Station_length > , the process of train i + 1 2 max b entering the station can be divided into the following four processes, as shown in Fig. 7.14. (1) Process 1:(acceleration +) constant speed + braking + constant speed + braking (① in Fig. 7.14). (2) Process 2: acceleration + braking + constant speed + braking (② in Fig. 7.14). (3) Process 3: acceleration + constant speed + braking (③ in Fig. 7.14). (4) Process 4: acceleration + braking (④ in Fig. 7.14). The existence of process 3 and process 4 depends on the specific parameter value. The derivation of the arrival speed (V(t0)) and arrival position

Speed

(P(t’),V(t’))

A

Line speed limit D

Platform speed limit

(P(t),V(t))

B

C Platform Position

P1

FIG. 7.13

P2

Station_Pos

Schematic diagram of train i + 1 arriving station in Case 1.

243

7.2 Cooperative control

Speed (P(t’),V(t’)) Line speed limit

A D

Platform speed limit E

(P(t),V(t))

F

C

B Platform P1

FIG. 7.14

P2 P3

Position

Station_Pos

Schematic diagram of train i + 1 arriving station in Case 2

(P(t0)) of tracking trains in each process is no longer carried out. Interested readers can refer to reference [20] for derivation.

7.2.3 Multitrain cooperative control with real-time interval adjustment [20] As trains cannot override between stations, track occupation conflict is very common with the increasing density of rail transit. Especially on single track where only one type of train operates, such as subway and highspeed railway. These conflicts will cause the driver to be forced to brake to avoid breaking out of the MA. When the train ahead slows down or even stops, the delay will spread backward. This phenomenon will cause additional train delay, train graph disturbance and energy consumption. If the train can be informed of this conflict in time to adjust the driving strategy, the above phenomena can be avoided, the train delay time can be reduced and the line capacity can be improved, as shown in Fig. 7.15. 7.2.3.1 Multitrain cooperative control with real-time interval adjustment Assuming a single line, the train cannot override in the section. According to the two train cooperation method proposed in the previous section, based on the known arrival process of the tracking train and combined with the quadratic optimal control theory, a real-time train interval adjustment algorithm can be established. The algorithm maintains the regularity of the headway of the railway network by adjusting the running time of the train in each section. Firstly, some observation points will be set along the line. The section length between observation points is equal. Through these observation

244

7. Novel methods for improving transport capacity

Time Before adjustment After adjustment

Distance

FIG. 7.15

Improve the capacity of bottleneck area by adjusting train speed.

points, we can know the arrival time aki of the k train at position i. In order to make the train flow at equal intervals, it is necessary to control the time aki when the train k reaches the observation point i. The relationship between the arrival time aki and the running time tki1, i of train k on the line of section (i  1,i) is as follows: aki ¼ aki1 + tki1,i

(7.5)

The time interval relationship between k  1 and k trains at observation point i at time t is: hki ¼ pki  pk1 i

(7.6)

pki

is the departure time of the kth train at position i. Obviously, if it does not stop, aki ¼ pki , it can be obtained: hki ¼ hki1 + tki1,i  tk1 i1,i

(7.7)

hki can be changed by adjusting tki1, i. The time when all trains arrive at observation point i before and after adjustment can be represented by the symbols in Table 7.2. The arrival time of the train that has passed the scheduled point cannot be adjusted and remains the original value. Where eki (t) is the optimal adjustment time when the kth train reaches the ith observation point at time t. When there are N trains in the system, the mean E(h) of the ith observation point at time t can be expressed as: XN k h H k¼2 i Eð h Þ ¼ (7.8) N1

245

7.2 Cooperative control

TABLE 7.2 Arrival time of train at observation point i. Train number

Actual or scheduled arrival time

Adjusted arrival time

1

a1i

a1i

…

…

…

k1

ak1 i

ak1 i

k

aki

pki ¼ eki (t)

k+1

ak+1 i

pk+1 ¼ ek+1 i i (t)

…

…

…

N

aN i

N pN i ¼ ei (t)

Where H is the specified interval and is a fixed value. The variance Π(t) can be expressed as: 2 XN  k h  H i k¼2 ΠðtÞ ¼ (7.9) N1 (1) Application of quadratic optimal control in train cooperative control The optimal control problem can regard the control system as a “black box.” People act on it with a behavior called “input,” and get a result called “output” through it. There is an important thing between “input” and “output,” which is called the state of the system. The system is described by a linear (discrete or continuous) equation of state. The performance index J is a quadratic function of state vector and control vector, and the optimal performance function can be achieved by solving the control strategy. Reference [23] presents a quadratic optimal control method to solve the multiagent speed convergence control problem. This method minimizes the performance index equation by local information and solving Hamilton-Jacobi-Bellman (HJB) equation. The general form of the system state equation is: X i ¼ A i X i + Bi u i + Bi

X jN i

Fij Yj

(7.10)

where, Xi  Rq, ui  Rm, q and m represent the dimensions of state space; Ai i iP ij j and B are taken as 1 below; B jNiF Y is the interaction term, Fij is the interaction coefficient, which is used to ensure the compatibility of matrix dimension on the input and output channels of each agent, and Ni is the neighbor of agent i. Neighbors are defined as a collection of agents who can exchange their own information with each other through the

246

7. Novel methods for improving transport capacity

TOA4

FIG. 7.16

TOA3

TOA2

TOA1

Agent topology.

communication network. Assuming that the train can obtain the interval information between it and adjacent trains, the train on the line is abstractly represented by agent (TOA), as shown in Fig. 7.16. According to Eq. (7.10), the state equation of train cooperative control system is obtained: X j hki ¼ hki1 + ui + Fij hi1 (7.11) jN i Thus, the running time of train k on the line of section (i, i  1) can be obtained: X j i tki1,i ¼ tk1 Fij hi1 (7.12) i1,i + u + jN i (2) Train real-time interval adjustment algorithm Step 1: set E0 and σ 0. Calculate train interval variance σ 2(h) and mean E(h), when E(h) > E0 or σ 2(h) > σ 0, perform the following steps. Step 2: the system state transition equation is: X j hki ¼ hki1 + ui + Fij hi1 jN i P T ij k k Step 3: give the system performance index J ¼ N i¼0(hi  hi1) Q ij k k1 (hi hi ), where Q is a symmetric positive matrix [23]. Step 4: design the feedback gain matrix  K(k) and solve the Riccati equation.  1 1 Kðk + 1Þ ¼ 2  Ni  Qij   KðkÞ Ri KðkÞ 2 Step 5: solve the optimal control rate. 1  1 u∗j ¼   Ri  Ki  Hi 2  1 Fij ¼ 2  Ki  Qij

247

7.2 Cooperative control

Step 6: given the running time tk1 i1, i of the train ahead, the running time of train k can be obtained. X j i tki1,i ¼ tk1 Fij hi1 i1,i + u + jN i Step 7: know the train operation time tki1, i, operation distance (observation points i  1 to i), line condition and train characteristics, and solve the train driving curve. Step 8: calculate the variance σ 2(h) and mean E(h) of train interval. When E(h) < E0 or σ 2(h) < σ 0 stop, otherwise return to step 2. 7.2.3.2 Train cooperative control combined with dispatching From the practical application, the current dispatching and train control mode is mainly the combination of manual dispatching and driver driving, and the two achieve mutual coordination by telephone, as shown in Fig. 7.17. When the train is late, the dispatcher is responsible for adjusting the train schedule affected by interference (by taking appropriate dispatching measures, such as re-timing, re-sequencing and re-establishing route), so as to reduce potential negative consequences (train delay); The driver is responsible for controlling the delayed train (by taking appropriate driving actions, i.e., acceleration, cruise, taxiing and braking) to arrive at the station at the time specified by the train dispatcher. The problem faced by the dispatcher is the well-known real-time traffic management problem, and the driver is confronted with the train control problem [24]. With the increasing demand for transportation services, railway traffic management and train operation control have been widely innovated in improving operation efficiency and automation. One is the development of dispatcher support system, the other is the development of driver support system. The former focuses on supporting the cooperation between the dispatcher and the traffic management system on the infrastructure side, and the latter focuses on minimizing the driving error by introducing automatic operation on the train side. These two areas have achieved success respectively, but each area lacks some benefits of the other. Because in the strategy of dispatcher support system, it assumes that the train runs completely according to the instructions, and its performance depends on the accuracy of traffic plan execution. The driver support system Traffic Management

Supervision

FIG. 7.17

Data Preparation

Rescheduling

Driver

Existing train dispatching-control structure diagram.

Train

248

FIG. 7.18

7. Novel methods for improving transport capacity

Improved train dispatching-control structure diagram.

focuses on train level optimization and has insufficient understanding of other trains in the network [25]. There is an important relationship between real-time traffic management and train control, because traffic related attributes will affect train related attributes, and vice versa. Solving these two problems in a sequential manner hides the potential improvement of train operation performance. Different researchers have proposed different solutions to the problem of poor coordination between real-time adjustment of train graph and operation control. Considering that the actual operation of the train is affected by the driver’s operation, Xiaolu Rao et al. Proposed a new optimization model combining the traffic management system with automatic train operation, as shown in Fig. 7.18. The improved train scheduling control model is composed of two closed-loop control loops: the external feedback control loop monitors the state of train traffic and infrastructure, detects deviations and conflicts, formulates a new production plan according to the optimization objectives, and transmits a new timetable. The internal feedback control loop at the lowest level is responsible for executing the command scheduling supported by the driver consultation system [25]. Improving the coordination ability of dispatching and control can not only reduce the negative impact of delay, but also improve the flexibility of high-speed railway operation, which plays a positive role in further improving the line carrying capacity and railway potential benefits.

7.3 Virtual coupling control system 7.3.1 Development of virtual coupling Around 2000, Bock, U and Bikker, G. of Ludwig-Maximilian University, Munich, Germany put forward the idea of virtual coupling, and wireless communication is used instead of mechanical connection technology to realize virtual coupling of different models and software versions [26]. From May 2015 to October 2017, European Railway Industry Association (UNIFE) and Spanish CAF jointly led the research team of rolling stock manufacturers including Siemens, Alstom and Bombardier, railway

7.3 Virtual coupling control system

249

operating companies and scientific research institutions, and launched Roll2Rail project [27]. It aims “To develop new, reliable rolling stock for more sustainable, intelligent and comfortable rail transport in Europe,” it includes eight working group, covers the areas of rolling stock, the working group 2 is the research of the next generation of train communication system which focus on developing wireless communication technology for train control [28–30]. The project has been concluded and the research has continued with the transfer to Shift2Rail. From 2018 to 2020, Shift2Rail is the planned project of the European union largest ever research and innovation program, Horizon2020, whose research covers all specialties across the entire rail transport system. It is divided into five topics (IP): IP1 is efficient and reliable rolling stock, IP2 is advanced transportation management/control system, IP3 is efficient and reliable infrastructure, IP4 is excellent railway service information system and IP5 is energy-saving and convenient railway freight technology. Virtual coupling consists of rolling stock and train control system, corresponding to IP1.2 Vehicle Control and Monitoring System (TCMS) and IP2.8 Virtual Coupling and train control technology respectively. According to the project plan, the IP1.2 vehicle communication technology has been completed in the previous Roll2Rail project [31]. Domestic and foreign scholars have studied the virtual coupling technology. 2019, Meo et al. studied the virtual coupling train control strategy and consider the communication link of time-varying delay virtual coupling control algorithm, proves that the virtual coupling can improve the transport capacity [32]. Liu et al. analyzes the train station in and out of the station operation characteristics, establish the station network topology, proposed in view of the virtual organization intelligent coordination control method, Xun studied the simulation implementation and performance testing of virtual coupling, proposed a virtual coupling tracking model at stations, and proved that virtual coupling has higher transport capacity than moving block [33]. In 2020, Muniandi proposed a blockchain-based train virtual coupling operation method to solve railway traffic conflicts, which solved the problem of train conflicts in virtual coupling technology [34]. Quaglietta calculated the transport capacity of train virtual coupling, tracking and re virtual coupling by establishing a mathematical model. It is proved that virtual coupling can improve the transport capacity, but the transport capacity of virtual coupling is low in places with switches [35]. In 2021, Cao established the dynamic model of virtual organization based on the dynamic model of virtual organization, and calculate the minimum tracking distance and the desired track distance, based on train operation process data of recursive least squares method for virtual to optimize the model parameters of the train operation organization, in the end, with the Beijing-Shanghai high-speed railway as the background,

250

7. Novel methods for improving transport capacity

The validity of this method is verified [7]. Carlo proposed an optimal control method for high-speed railway virtual coupling trains. In order to keep the safe spacing of the following workshops under virtual coupling conditions, a state space model of dynamic virtual coupling trains was established first, and then the optimal control equation was constructed by considering the constraints such as safe spacing and moving authorization. For the proposed constrained optimal control problem, an analytical algorithm was given, and the effectiveness of the proposed control strategy under different disturbances was verified by numerical simulation [32]. 7.3.1.1 Concept and principle of virtual coupling (1) The concept of virtual coupling Virtual Coupling is defined as follows in Shift2rail. In order to further improve transport capacity and adapt to the growth of railway demand, the concept of virtual coupling is put forward. Virtual coupling is based on vehicle-ground wireless communication and vehicle-vehicle communication for information transmission. Trains are separated by a relative braking distance. In the absence of any mechanical connection, multiple trains move synchronously on a single path, and trains are regarded as a single convoy [31]. Literature [34] defines that the virtual coupling system adopts centralized management of line data stations, centralized control of temporary speed limiting dispatching center, local vehicle-ground wireless communication to realize transmission of moving authority, interval line data and temporary speed limiting information, and interval occupation inspection and signal authority through track circuit. Information is transmitted between trains in the train group through vehicle-to-vehicle communication. The trains in the train group follow each other through the two-dimensional control mode of speed and distance. Train integrity is checked through the integrated train tail, and train location is realized through the passive transponder. Literature [35] proposed that virtual coupling is based on the relative braking distance, that is, the distance required to slow down to the speed of the train in front. The group trains connected by vehicle-vehicle communication run synchronically with the trains of the whole virtual coupling fleet to maintain the safety margin between them. Literature [7] proposed that virtual coupling refers to a marshaling mode in which multiple trains communicate with each other to realize the coordinated running of trains within a short tracking distance. Compared with the traditional train virtual coupling mode, virtual coupling can greatly shorten the tracking interval and improve the line capacity. In addition, virtual group is used instead of physical connection, which makes the group mode more flexible and compatible, and has the characteristics of short group time and high group intensity.

7.3 Virtual coupling control system

251

(2) Structure of virtual coupling train control system The train in virtual coupling mode runs in the form of a convoy, which is quite different from the single operation mode of the existing train. Therefore, compared with the existing train control system, the train control system using virtual coupling has undergone great changes in hardware structure. Virtual coupling train control system can be divided into onboard equipment, ground equipment and communication equipment according to its functional requirements. Compared with ETCS-3, it has great differences in functions of vehicleon-board equipment, ground equipment, and communication equipment. Among them, the difference of on-board equipment is mainly reflected in ATP, ATO and other equipment, and the Train Management System (TMS) equipment is added. The difference of ground equipment is mainly reflected in RBC and CI equipment. On the basis of vehicle-ground communication, vehicle-vehicle communication technology is added. Onboard equipment includes TMS(Train Management System), ATP, and ATO. In the virtual coupling fleet, the control strategy of the leading Train is different from that of other trains in the virtual coupling fleet, and the functions of the Train Management System (TMS) in the leading Train and the rear Train are different. TMS (Train Management System) is used by the head Train of a fleet to coordinate the behavior of the fleet, while other virtual trains use this System to check the integrity of the Train, and coordinate the virtual coupling and un virtual coupling of other trains in the virtual fleet. TMS consists of train management sensor module and train management communication module. Train management sensor to ensure high safety, high reliable measurement of speed, acceleration, position, train management communication module for the train management system, and other equipment between the communication. TMS obtains information from ground equipment about all trains on the line, including train position, serial number and operating status, train integrity and braking performance, and the running curve of the assembled fleet. TMS sends the location of the assembled fleet, serial numbers to ground equipment, and emergency braking curves to every train on the line. The team head car ATP of virtual coupling fleet and other trains in the virtual coupling the team of ATP function is different, first car of ATP computing based on absolute braking distance of overspeed protection curve, the other train of the virtual coupling fleet calculated based on the relative overspeed protection of braking distance curve, the speed of the car by monitoring the strict curve, to protect the virtual coupling the team from collisions and derailments. To listen to all the other train car command from the ground up, and the team in all other trains and two-way communication vehicle and the vehicle ahead, keep a relative with their vehicle braking distance, each time there is a new train with

252

7. Novel methods for improving transport capacity

virtual team organization, virtual all the trains in the virtual coupling the team to calculate the new overspeed protection curve. The function of ATO is to control the same emergency braking rate of the same fleet to ensure that the whole fleet runs at a safe distance. ATO should be able to obtain real-time information about the position, acceleration and speed of trains in a fleet to generate ATO curves so as to avoid collisions with trains with better braking performance ahead and maintain a safe distance between trains in a fleet. Ground equipment includes RBC, CI and other equipment. The RBC of the head car has different functions from the RBC of other trains in the virtual coupling team. The RBC of the head car sends the information of acceleration, position and speed of the train to the RBC, while the RBC of other trains in the virtual coupling team transfers the movement authority to the head car. In virtual formation, the interlock function is to ensure that the entire line must be locked until the entire fleet has passed the unlock. The virtual coupling communication structure as shown in Fig. 7.19, which includes vehicle-vehicle communication technology and vehicleground communication technology. The communication technology should meet the basic requirements of information exchange between formation trains, that is, the range of point-to-point communication should be wide, low delay and high reliability should be realized. Currently, 5G technology is recommended.

5G

5G Core Network

5G Core Network

ETCS Message: MA Gradient SSP

ETCS Message: MA Gradient SSP

5G

FIG. 7.19

VC Message: Speed Acceleration Location

Virtual coupling communication structure.

5G

253

7.3 Virtual coupling control system

VB

VA

B

Approaching train with shared route?

A

VA

VB EoA and leader speed reached??

VB

A

B

VA

B

Can not hold leader speed?

A

VB B

Approaching diverging junction?

VB`

VB

VB`

VA A

VA

B Is leader diverging? A

Approaching a train after the junction?

FIG. 7.20

Virtual coupling principle.

(3) Principle of virtual coupling train control system The process of train operation controlled by the virtual coupling train control system can be divided into the following four parts, namely, ETCS-3 level operation, virtual coupling operation, unintentional and intentional virtual coupling, as shown in Fig. 7.20. 1. ETCS-3 level operation When the train runs in ETCS-3 level, it judges whether the conditions of virtual coupling are met at all times. If the conditions of virtual coupling are met, the speed of the vehicles ahead and behind is judged. If the speed of the vehicles ahead is greater than that of the vehicles behind, the vehicles behind will accelerate first and then decelerate; if the speed of the

254

7. Novel methods for improving transport capacity

vehicles ahead is smaller than that of the vehicles behind, the vehicles behind will decelerate directly. 2. Group operation If the speed of the front and rear vehicles becomes the same, the front and rear vehicles run in groups. When the front and rear cars are in virtual coupling operation, the train should always judge whether the speed difference with the front and rear cars is within the allowed range. If it is within the allowed range, the train will run in virtual coupling; if not, the speed of the front and rear cars should be adjusted to make the train in virtual coupling operation state. The train in the virtual coupling operation process, but also always judge whether the train through the switch to un coupling operation, if the train run through the switch, then judge whether the train and virtual coupling team has the same route, if there is the same route, then virtual coupling, if there is different route, then do not need to virtual coupling. 3. Unintentional decoupling If the acceleration of the leader exceeds the max acceleration of the follower acceleration. Then the two trains will inevitably increase their separation. As the follower train unintentionally decouples from the leader, then it immediately switches back to a “Coupling” operational state so to reduce again the separation with leader as soon as motion resistances and/or traction power will allow that. In this operational state, speed vk and front position sk of the train at current time step tk, are again computed, since the train is momentarily decoupled from the leader. As mentioned, the decoupling is defined “unintentional” since it is not intentionally triggered by the signaling system to meet safety constraints (e.g., to prevent derailments at diverging junctions) but merely occurs because of temporary constraining operational conditions due to increased motion resistances (e.g., on a steep uphill) or limited traction power. 4. Intentional decoupling When a coupled train convoy approaches a diverging junction where trains split over different routes, nonnegligible safety risks arise. Switches might not have enough time to be safely moved and locked in between trains, potentially causing derailments. For safety reasons, trains will need to be outdistanced by an absolute braking distance at diverging junctions so that a train can safely stop should the switch not properly be set and locked. In case a coupled train is going to diverge from its leader, the vehicle-vehicle communication layer will provide the location of the diverging junction which represents the supervised location SvL. The EVC will compute the braking Indication Point IP decoupling where the train needs to start braking to intentionally decouple from the leader.

255

7.3 Virtual coupling control system

7.3.2 Improvement of transport capacity by virtual coupling technology 7.3.2.1 Virtual coupling technology improves the transport capacity of high-speed railway Shift2Rail, which evaluates the capacity of virtual coupling technology, uses the example of a direct high-speed train from Rome to Bologna with a distance of 305 km and a total journey time of 1 h 55 min from origin to destination, with a time difference of 15 min. Virtual coupling technology, applied to high-speed rail, can significantly improve transport capacity, as shown in Table 7.3, with virtual coupling technology, a 6-min tracking interval can be achieved at a price of 45 dollars, while with current technology, a 15-min tracking interval can be achieved at a price of 51.4 dollars. For high-speed railway, as a result of the train running speed is higher, based on the relative speed of the braking distance than the braking distance based on absolute velocity is large, so the virtual organization technology can greatly reduce the train after the distance, the distance between the long and high-speed railway station, can provide enough space for coupling reconciliation process, virtual organization are easier to implement. The application of virtual coupling technology in high-speed railway also has its shortcomings. If the trains of virtual coupling do not enter the same track, they need to be unmarshaled before entering the station, so the technology mainly improves the interval tracking ability. The time between train departure and arrival tracking is the main factor limiting the transport capacity for high-speed railway, which is related to the length of throat area, speed limit, length of departure section and other factors. Therefore, virtual coupling has limited space for improving the transport capacity of high-speed railway stations. High-speed train running at high speed will increase the security risk of vehicle-vehicle communication. Train braking characteristics are different, resulting in more complex train management. Virtual coupling allows trains in the same fleet to queue up and stop on the same platform. If passengers are not given enough information, this can lead to confusion and boarding on the wrong train. In addition, platforms can be crowded as passengers traveling in different directions have to go to the same platform [32].

TABLE 7.3 Application of virtual coupling technology in high-speed railway. Train service

Frequency

Cost

Current

Every 15 min

45.9 dollar

New

Every 6 min

51.4 dollar

256

7. Novel methods for improving transport capacity

7.3.2.2 Improvement of subway transport capacity by virtual coupling technology A tube line 7 km from London in the United Kingdom, running from Lancaster to Liverpool Street, London, with eight intermediate stops and a journey time of 15 min (taking into account passengers’ time on/off the platform). Trains run every 2 min in headway and cost £2.40 one way. By bus, journey times will be increased to 50 min at a cost of £1.50, while the frequency of bus journeys will be reduced to every 6 min. A 45-min one-way trip from London Lancaster to London Liverpool Street costs just £0.92. Cycling or walking is indeed free, with a bike trip taking about 35 min and a walk almost an hour and a half [31]. For the Metro, as shown in Table 7.4, 45 s of headway can be achieved with a one-way fare of £2.70 when trains use virtual coupling technology. When moving blocks are used, 2 min of headway can be achieved and a single ticket costs £2.40. When trains adopt virtual coupling technology, shorter tracking interval can be realized. The difference of braking performance of subway trains is small, so it is easier to realize virtual coupling. In addition, urban rail transit is generally a station without wiring, and the trains before and after operate in the same lane, so virtual coupling can give full play to its technical advantages. According to the investigation of passengers’ travel preference, passengers are not willing to spend more fare to reduce waiting time. Therefore, reducing the tracking interval of subway to less than 1 min will not increase the attractiveness of the railway section, and the current headway can already meet the travel needs of passengers. But when subway tracks are more than 6 min apart, passengers are willing to pay more to reduce wait times. On some tube lines, such as the London Victoria Line in the United Kingdom, 1-min tracking intervals have been achieved using existing signaling systems. Therefore, for these subway systems, the implementation of virtual coupling will not increase the attractiveness of the service itself from the perspective of passengers, while for the extremely dense and crowded suburban network, virtual coupling can further shorten the interval between subway trains.

TABLE 7.4 Application of virtual grouping technology in subway. Train service

Frequency

Cost

Current

Every 2 min

2.40 GBP

New

Every 45 s

2.70 GBP

257

7.3 Virtual coupling control system

7.3.2.3 Improvement of freight transport capacity by virtual coupling technology The freight line from Hamburg to Rotterdam is 503 km long and the average running time between these two locations is around 7 h and a half. It is assumed that three freight trains per day depart from Hamburg with destination Rotterdam and that each train transports 8 containers (i.e., 24 containers per day). The cost to deliver the goods by means of the freight train is around €1235 per container. This case study is addressed to understand stated delivery choices of the interviewed sample concerning the current situation and the future scenarios of a more frequent and flexible rail freight delivery service available (56 containers per day rather than 24) for an increased marginal delivery cost, as shown in Table 7.5. When trains adopt virtual coupling technology, shorter tracking interval can be realized. The advantage of virtual coupling is that it has higher flexibility and higher transport capacity. In freight transport, the size of virtual coupling yards can be reduced because the marshaling and unmarshaling of trains takes place on tracks. Because of the longer distance between stations, virtual coupling is easier to achieve, improving the current management complexity caused by frequent dismarshaling of shorter trains.

7.3.3 Technical difficulties of virtual coupling 7.3.3.1 Virtual group security issues (1) Safety problem of switch position In the switch position, when the team do not have the same route of organization, as shown in Fig. 7.21, the team will be in front of the switch solution, the switch needs to transform, and switch transformation takes time, if there is no enough time to transform or locking switch in the corresponding position, at this time the train through the switch are at risk of derailment. Therefore, in this case, the train needs to slow down and wait for the switch, when the switch is successful, the train continues to run. Therefore, in the process of switch conversion, the train operation efficiency is low, but also there will be safety problems, once the train speed control is not reasonable, it is easy to cause the derailment phenomenon, and will affect the train operation efficiency. TABLE 7.5 Application of virtual coupling technology in cargo transportation. Train service

Frequency

Cost

Current

24 per day

€1235

New

56 per day

€1420

258

7. Novel methods for improving transport capacity

Safety challenges Distance at diverging junctions B

FIG. 7.21

A

Security problem of virtual coupling switches.

(2) Vehicle-vehicle communication Under the virtual organization of train running speed is higher, as shown in Fig. 7.22, train in the virtual organization, according to the car get limber velocity and acceleration of information communication technology, if you can’t get accurate information in a timely manner, will be very serious consequences, if the front of the train emergency brake, the train did not timely to receive this information, it is possible collision, Therefore, the communication security requirements are high, and a high security frequency must be selected. 7.3.3.2 Technical problems with virtual coupling (1) Control policies Under virtual coupling, whether the marshaling fleet is controlled and scheduled by a centralized CTC or by a separate control needs further study. Whether interlocking is centrally managed by CTC or can be set directly by on-board equipment also needs further study.

Communication frequency Radio Block Center V2V comm.

B

FIG. 7.22

Virtual group communication security issues.

A

7.3 Virtual coupling control system

259

ATO interface ATO

Safety margin

ATO

B

Safety margin

A

Safety margin

FIG. 7.23

Virtual ATO system grouping.

(2) ATO ATO to control the same fleet has the same emergency braking rate, so as to avoid collision with the front train with better braking performance; The ATO should also be able to obtain information about the position, acceleration and speed of the train ahead, as shown in Fig. 7.23, to maintain a safe distance between trains in a convoy. (3) Train location and integrity information Since virtual coupling is based on moving block, train control system needs to realize train occupancy check according to train position report and train integrity information, so on-board equipment should send train position report and train integrity information to RBC in real time. If the virtual coupling train is regarded as a whole vehicle, and only the leading vehicle reports the position information, all the position information and train integrity of the rear vehicle should be successively sent to the leading vehicle through vehicle-vehicle communication, which increases the complexity of the system. Moreover, from the point of view of ground equipment, the rear car no longer reports the position, and the train length reported by the head car changes constantly with the train running interval, which complicates the RBC processing logic. (4) Auto-passing phase separations When there is a phase division zone ahead of the line, the RBC sends the starting point and length of the phase division zone to the onboard device. The onboard equipment outputs the overphase control signal when the locomotive is a certain distance from the starting point of the phase division area, and cancels the overconfidence signal when the locomotive is a certain distance from the end point of the overphase division area, so as to complete the auto-passing phase separations function.

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7. Novel methods for improving transport capacity

If the virtual coupling train processes the overphase information as a whole vehicle, the time of the overphase output of the following train is advanced, and the time of the overconfidence signal cancelation of the preceding train is backward. When the number of trains is too large, the virtual coupling trains may stop in the phase separation area because the power failure time is too long. If the head car calculates the out-ofphase timing of each train according to the position of each train, and then sends it to the corresponding rear car through vehicle-vehicle communication, the processing of on-board equipment will become too complicated. Therefore, from the Angle of automatic phasing, the on-board equipment of virtual coupling train should carry out auto-passing phase separations function separately. 7.3.3.3 Virtual coupling operation problems (1) Platform length In infrastructure, when the train bound for different directions, the team length will be longer, if the station track is shorter, makes part of the train on the track, part of the train on the track, do not use for the control of the train, therefore to extend the length of the station track, to allow more trains into a station at the same time, The realization of the same platform in line after line parking. Therefore, it is necessary to adjust the platform length to the average length of the train fleet. (2) The parking Trains in different directions stopping at the same station may mislead passengers. To avoid confusion, trains bound for the same destination may be assigned to the same platform. Another solution is to divide platforms into sections, each representing a different destination for a different train. This isolation can be achieved through isolation plates or platform doors, and train lengths need to be better adapted to the process of unmarshaling and marshaling. (3) Train operation specifications From an operational point of view, existing train operation specifications are based on a single train, rather than relying on the entire fleet. For example, the running time of each train no longer depends solely on its technical characteristics and route, but on the operating characteristics of other trains in the same group (segment). (4) Vehicle-ground communication protocol The vehicle-ground communication protocol was changed so that information about line conditions was transmitted only to the head car of the coupling fleet, rather than to each train that was part of the coupling fleet.

References

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[23] E.S. Kazerooni, K. Khorasani, Semi-decentralized optimal control of a cooperative team of agents, in: IEEE International Conference on Systems Engineering, SoSE’07, 2007, pp. 1–7. [24] X.J. Luan, Y.H. Wang, B.D. Schutter, et al., Integration of real-time traffic management and train control for rail networks—Part 1: optimization problems and solution approaches, Transp. Res. B 115 (2018) 41–71. [25] X.L. Rao, M. Montigel, U. Weidmann, Potential railway benefits according to enhanced cooperation between traffic management and automatic train operation, in: 2013 IEEE International Conference on Intelligent Rail Transportation Proceedings, 2013. [26] U. Bock, G. Bikker, Design and development of a future freight train concept—"virtually coupled train formations", IFAC Proc. Vol. 33 (9) (2000) 395–400. [27] E. Peris, J. Goikoetxea, Roll2Rail: new dependable rolling stock for a more sustainable, intelligent and comfortable rail transport in Europe, Transp. Res. Proc. 14 (2016) 567–574. [28] K. Yang, M. Berbineau, J.-P. Ghys, et al., Propagation measurements with regional train at 60ghz for virtual coupling application, in: 11th European Conference on Antennas and Propagation, Paris, France, 2017. [29] P. Unterhuber, S. Sand, M. Soliman, et al., Wide band propagation in train-to-train scenarios-measurement campaign and first results, in: 11th European Conference on Antennas and Propagation, Paris, France, 2017. [30] I. Val, A. Arriola, P.M. Rodriguez, et al., Wireless channel measurements and modeling for TCMS communications in metro environments, in: 11th European Conference on Antennas and Propagation, Paris, France, 2017. [31] Shift2Rail, 2020. https://projects.shift2rail.org/s2r_ip2_n.aspx?p¼MOVINGRAIL. [32] C. Di Meo, et al., ERTMS/ETCS virtual coupling: proof of concept and numerical analysis, IEEE Trans. Intell. Transp. Syst. 21 (6) (2019) 2545–2556. [33] L.I.U. Ling, W. Ping, W.E.I. Wei, et al., Intelligent dispatching and coordinated control method at railway stations for virtually coupled train sets, in: 2019 IEEE Intelligent Transportation Systems Conference (ITSC), IEEE, 2019, pp. 607–612. [34] G. Muniandi, Blockchain-enabled virtual coupling of automatic train operation fitted mainline trains for railway traffic conflict control, IET Intell. Transp. Syst. 14 (6) (2020) 611–619. [35] E. Quaglietta, M. Wang, R.M.P. Goverde, A multi-state train-following model for the analysis of virtual coupling railway operations, J. Rail Transp. Plann. Manage. 15 (2020) 100195.

C H A P T E R

8 Influencing factors and calculation methods for carrying capacity of high-speed railway 8.1 Definition and characteristics of carrying capacity of high-speed railway 8.1.1 Definition of carrying capacity of high-speed railway The transport capacity of a high-speed railway, which depends on the setup of its fixed facilities, is generally called the carrying capacity, which is normally measured in terms of district or direction, and expressed as the maximum number of trains or train pairs of standard weight that can be handled by the fixed facilities in unit time based on the given types of the locomotive and vehicles and the specific traffic organization. The carrying capacity, as it depends to a certain extent on the staff coordination, and the rational use of the fixed facilities and rolling stock is not unchangeable, but will improve with the development of the technical equipment and traffic organization method. The purpose of calculating the carrying capacity is to rationally schedule the transportation tasks of high-speed railways, so as to ensure that they better serve the regional economic development [1]. The carrying capacity mainly includes station carrying capacity and district carrying capacity. 8.1.1.1 Definition of station carrying capacity The station carrying capacity refers to the maximum number of passenger trains that can be received and dispatched on the arrival and departure tracks of a station in a day and night under the given timetable graph, station equipment, operation nature, and technical operation process of passenger trains.

Theory and Technology for Improving High-Speed Railway Transportation Capacity https://doi.org/10.1016/B978-0-323-99700-3.00007-4

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Copyright © 2023 Elsevier Inc. All rights reserved.

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The factors influencing the station carrying capacity mainly include: (1) Times for trains to occupy the arrival and departure tracks The trains handled at high-speed railway stations fall into four scenarios, namely originating trains, arrival trains, passing trains, and turn-back trains; furthermore, originating trains and arrival trains might be suburban trains or long-distance trains. The time for a train to occupy the arrival and departure track of a station depends on the technical operation procedure of the station, and normally with low dispersion except that for turn-back trains. Since the arrival-departure time and the time for the train set entering and exiting the service workshop are basically fixed in the timetable of 1 day and night, no time for waiting to depart or transfer should be involved. (2) Proportion of trains received at and dispatched from the station under different scenarios The station carrying capacity is calculated as it is in linear relation with the number of trains handled based on the effective timetable graph, however, it is also related to the proportion of scenarios to be handled. For example, the carrying capacity of a station mainly handles passing trains would be smaller than that mainly handles originating trains and arrival trains. (3) Imbalance of arrival and departure of trains The arrival and departure times of passenger trains at a high-speed railway station are normally scheduled in the timetable graph of the station, so arrival/departure surges occur occasionally. The capacity of the arrival and departure tracks is awkward in peak hours, but wasted in off-peak hours. The greater the imbalance is, the more serious the capacity is wasted. Therefore, the imbalance of arrival and departure of trains has a serious impact on the station carrying capacity. (4) Idle time The idle time of arrival and departure tracks means the rational period during which the tracks cannot be used for receiving or dispatching passenger trains as normal. It can comprehensively reflect the impact of the above factors on the capacity of the arrival and departure tracks, and is usually expressed by the idling coefficient, namely, X tf αf ¼ (8.1) Mp ð1440  ts Þ

8.1 Definition and characteristics of carrying capacity of high-speed railway

265

where αf—the idling coefficient; Mp—the number of arrival and departure tracks for passenger trains; ts—the period in a day and night specified by the station, during which no P passenger train should be received or dispatched, in min; tf—the total idle time of all the arrival and departure tracks of the station in a day and night, in min. (5) Number of arrival and departure tracks for passenger trains The carrying capacity of the arrival and departure tracks of a station is proportional to the number of arrival and departure tracks for the receipt and dispatch of passenger trains. (6) High-speed Railway Station Layout There are three layouts of high-speed railway station: through type station, stub-end station, and combined station. In the case of stub-end station, as the receipt and dispatch of trains, placing-in and taking-out of train sets, and locomotive entering and leaving the depot are carried out through one station throat, whose carrying capacity is accordingly awkward, resulting in an increase in αf of the arrival and departure track and a decrease in its carrying capacity. 8.1.1.2 Definition of district carrying capacity The district carrying capacity is defined as the maximum number of trains or train pairs that can be released or handled by the fixed facilities in a railway district and related stations to a certain service level within the specified time for passenger train operation services under certain passenger transport demands, based on the specific type of EMU and the specified transportation organization method. Specifically, it may further involve the all-day carrying capacity, peak-hour carrying capacity, capacity for long-distance train lines, and capacity for short-distance train lines. The all-day carrying capacity refers to the maximum number of passenger train pairs or passenger trains that can be handled within the specified time for passenger train operation services. The peak-hour carrying capacity refers to the maximum number of passenger train pairs or passenger trains that can be handled per hour in the peak hours of traffic, without considering any disturbance or buffer time. The capacity for long-distance train lines refers to the maximum number of passenger train pairs or passenger trains (each of which has a length of haul greater than or equal to the length of the district) that can be handled within the specified time for passenger train operation services, under the premise that the portfolio of

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8. Calculation methods for carrying capacity

trains running at different speeds in the passenger traffic district remains unchanged and the specific service requirements are met. The capacity for short distance train line refers to the maximum number of passenger train pairs or passenger trains (each of which has a length of haul less than the length of the district) that can be handled within the specified time for passenger train operation services after the capacity for long-distance train lines that has been consumed by the trains is deducted, under the premise that the portfolio of trains running at different speeds in the passenger traffic district remains unchanged and the specific service requirements are met. The district carrying capacity can be calculated in terms of the following fixed facilities: (1) The carrying capacity calculated in terms of section mainly depends on the number of its main tracks, its length, the profile of line, the type of locomotive, and the types of signal, interlocking and block devices. (2) The carrying capacity calculated in terms of station mainly depends on the number of its arrival and departure tracks, the setting of throat switch, the number of humps and draw-out tracks, and the types of signal, interlocking and block devices. (3) The carrying capacity calculated in terms of maintenance window mainly depends on its duration and mode. (4) The carrying capacity calculated in terms of power supply equipment of electrified railway mainly depends on the traction substations and the overhead contact system (OCS). The calculation results may be different, and the fixed facility with the lowest capacity will limit the carrying capacity of the district. Accordingly, the district carrying capacity is equal to that calculated in terms of such fixed facility.

8.1.2 Characteristics of carrying capacity of high-speed railway 1. Imbalance of capacity consumption in different periods High-speed railway lines mainly serve passenger transport. The rules of passenger flow generation and change are different in different seasons, the characteristics of passenger flows on weekdays are different from those at weekends, and the passengers travel at different frequencies at different times of day. As a result, high-speed railways are quite different from the conventional ones that seek balanced transportation organization as far as possible and make full use of the district carrying capacity. Since ordinary-speed railways are used for operating freight trains, on the whole, the capacity consumption is relatively balanced at different times of day.

8.1 Definition and characteristics of carrying capacity of high-speed railway

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2. Significant difference between calculated capacity in theory and available capacity in fact In view of the characteristics of passenger flow of the high-speed railway, although more train paths can be theoretically planned in the timetable graph, in fact, they can attract and handle different passenger transport volumes for their different temporal and spatial conditions. Compared with the conventional railway lines, a high-speed railway line shows a large gap between the capacity calculated by the traffic volume and the calculated capacity in theory. 3. Amplification of influence of train stopping time and additional time for starting and stopping As for high-speed railways, the influence of train stopping time and additional time for starting and stopping has become more significant than that of headway, and the capacity deduction due to stopping of high-speed trains has become an important term in capacity calculation. Therefore, there exists amplification of the influence of train stopping time and additional time for starting and stopping in the case of high-speed railways, which is quite different from the case of the conventional railways. 4. Coexistence of relatively insufficient capacity for long-distance train lines and relatively surplus capacity for short-distance train lines The window refers to the time reserved for construction and maintenance by not setting the train paths in the timetable graph or by adjusting or reducing the train paths, and it falls into construction window and maintenance window according to its purpose. As shown in Fig. 8.1, due to the use of vertical rectangle windows with unified time for the power cut and restoration of power supply, the timetable graph of high-speed railway is a discontinuous temporal and spatial plane cut

FIG. 8.1 Schematic diagram of vertical comprehensive maintenance window of highspeed railways.

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8. Calculation methods for carrying capacity

by the window period, resulting in two special triangular areas in the upand down-directions at the upper and lower left corners and the upper and lower right corners respectively; no train path throughout the whole line can be set in these four triangular areas so that there are long-distance train lines and short distance train lines in terms of setting the train paths and capacity utilization. The capacity for a long-distance train line can be divided into segments for several short-distance train lines; however, the capacities for several short-distance train lines cannot be combined for a long-distance train line. As the line length and window period increase, the capacity for long-distance train lines decreases. Therefore, the capacity consumption of high-speed railways shows the characteristics that its carrying capacity in a direction is less than that of a district, and relatively insufficient capacity for long-distance train lines and relatively surplus capacity for short-distance train lines coexist. In contrast, the daily maintenance window of a conventional electrified railway is typically not more than 2 h and in the daytime, mainly for the maintenance of power supply equipment, especially the OCS for traction, and the operation is relatively simple. Thus the timetable graph of a conventional electrified railway is significantly different from that of a high-speed railway.

8.2 Calculation methods for carrying capacity of high-speed railways 8.2.1 Calculation methods for station carrying capacity The calculation methods for station carrying capacity mainly include the simulation method, timetable graph compression method, formula method, direct calculation method, and graphical method. 1. Simulation method In the simulation method, an optimization model for routing of the arrival and departure tracks and the station throat will be built first. On this basis, the train arrival and departure at the station will be set reasonably according to the process of technical operations at the station and by strictly following the standard times for relevant operations, and finally the number of trains that can pass the station will be determined. This method takes the carrying capacity of the station throat and that of the arrival and departure tracks as a whole, and is able to simulate the station carrying capacity under different operation schemes, diagnose and reveal problems in the station layout through system simulation, and provide a basis for finally realizing the ultimate optimal carrying capacity of the station [2].

8.2 Calculation methods for carrying capacity of high-speed railways

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According to the overall idea of this method, the station carrying capacity is calculated in four steps, as shown in Fig. 8.2 [2], namely determining the time standards for relevant operations at the station, depicting the network topology of station, building the carrying capacity models, and simulating the process of operations for trains at the station by computer. (1) Determining the standard times for relevant operations at the station Before calculating the station carrying capacity, the standard times for relevant operations at the station shall be determined. These standard times mainly cover the standard time for occupancy of the station throat, the standard time for occupancy of the arrival and departure tracks, and the standard headway. The time of EMU trains occupying the station

FIG. 8.2

Overall idea of simulation method.

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throat is the sum of the direct occupancy time and the time for route setting and release, and specifically it includes the time of occupying the station throat for train receiving, the time of occupying the station throat for train dispatching, the time of occupying the station throat and the arrival and departure tracks for nonstop passing trains, the occupancy time for transfer of EMUs, and so on. (2) Depicting the network topology station This step is to group the switches in the station throat, so as to simplify the station layout, and on this basis, to depict the network topology of the station, where the interfaces between the main track and the sections, the switches on the arrival and departure tracks, and those in the station throat are abstracted as point in the graph, and the lines connecting the points are abstracted as edges with costs and capacities defined. (3) Building the carrying capacity models This step is to build the carrying capacity model of station throat and that of arrival and departure tracks, so as to coordinate the two capacities, and to build the overall carrying capacity model of a high-speed railway station. To build the carrying capacity model of station throat, the main approach is to optimize the station operation routes. For the shortest receiving and dispatching route, the route between the corresponding two nodes shall be taken as the first choice, and then it is necessary to consider the harmony between the quantity of remaining parallel operations at the station and the shortest route, which means maximizing the quantity of parallel operations from the perspective of space and building a route untwining model with crossing occupancy time of routes in the station throat from the perspective of time, so as to finally build the carrying capacity model of the station throat. To build the carrying capacity model of arrival and departure tracks, it is necessary to consider the factors concerning the rational use of arrival and departure tracks, mainly including the conformity of the train receiving and dispatching operations to the established occupancy scheme of the arrival and departure tracks; the exclusivity of the arrival and departure tracks; the time requirements for all types of trains dwelling at the station for operation; ensuring uninterrupted receipt and dispatch of trains, reducing the time of trains waiting for routes and ensuring the balance of occupancy time of arrival and departure tracks. The ultimate station carrying capacity cannot simply be the smaller of the carrying capacity of station throat and that of arrival and departure tracks, and the harmony between the operations of the two subsystems shall be fully considered. Only the station receiving and dispatching

8.2 Calculation methods for carrying capacity of high-speed railways

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capacity that can realize the harmony between the operations of the two subsystems is the effective station carrying capacity. When this harmony is realized, and considering the constraints between the two subsystems, the subject station is regarded as a node in the railway network, so that the corresponding peak-time carrying capacity is the train flow at the node, and the calculation model for the overall station carrying capacity is built accordingly. (4) Operation procedure design for high-speed railway stations by simulation This step is to simulate the procedure of train operations at station based on the input relevant models, the standard times of train operations at station, and the proportion of types of trains received and dispatched. The first thing is to determine the basic categories of events that will happen, mainly departure event and arrival event, for which the corresponding operation subprocedures are then selected. The second thing is to determine the types of train operations, including originating trains, arrival trains, passing trains (including passing trains with stopping and nonstop passing trains), and turn-back trains. The third thing is to handle the operations according to the corresponding procedures for different types of trains at the station. Finally, the parameters such as the starting and ending time of each train occupying the station throat and arrival and departure track during peak hours, tracks occupied, train types and speed levels are output, and the number of trains received at and dispatched from the station are counted by train type, so as to obtain the combined station carrying capacity during peak hours. The above is shown in Fig. 8.3 below [2]. 2. Timetable graph compression method The International Union of Railways has issued UIC406, which introduced a method for calculating the carrying capacity. This method is based on the existing timetable graph of the railway district and compresses the redundant time in the timetable graph on the premise of not changing the structure of the existing timetable graph and meeting the standard interval required for the safe operation of trains. Finally, the track section carrying capacity is calculated based on the compressed occupancy time of the train routes in the existing timetable graph of the district and by considering certain utilization rates and additional time rates. Or the track section carrying capacity under different service quality can be calculated by densifying the timetable graph by adding train routes in the idle time of the timetable graph. According to UIC406, and considering the characteristics of existing timetable graphs for different track sections in China, the main steps to calculate the district carrying capacity based on compressing intervals

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8. Calculation methods for carrying capacity

FIG. 8.3 Designed process of simulation for operations at high-speed railway stations.

8.2 Calculation methods for carrying capacity of high-speed railways

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in the timetable graph include: train route ordering, determining the compression time of each train, determining the compression time of train sets, compressing and calculating the carrying capacity by considering the cross-line trains. The practice shows that this method can deal with the relationship between a large number of complex train routes in different types of railway districts in China, fully respects the structure of the existing timetable graph of railway district and train route sequence, compresses and densifies the existing timetable graph on the basis of fully considering the relationship between different types of intervals at stations in railway districts, and calculates the railway district carrying capacity in a precise, accurate, and satisfactory manner by taking the cross-line trains into account. 3. Formula method The station carrying capacity can be calculated according to the following formula [3]:   Mp ð1440  ts Þ 1  αf Np ¼ (8.2) to where Np—the station carrying capacity, in trains; αf—the idle coefficient of arrival and departure tracks for passenger trains. According to the simulation and regression analysis, the regression formula for calculating αf is αf ¼ 0:3181  0:000887N p + 0:2236αp + 0:2602αb

(8.3)

to—the average time of one passenger train occupying the arrival and departure tracks, in min; and to ¼ αp top + αb tob + αs tos + αd tod

(8.4)

where αp, αb, αs, αd—the proportions of passing passenger trains, turn-back ones, originating ones and arrival ones to the total number of passenger trains received and dispatched in 1 day and night respectively, αp + αb + αs + αd ¼ 1; top, tob, tos, tod—the times of the types of trains mentioned above occupying the arrival and departure tracks respectively, in min. top ¼ tp + tps + ts tob ¼ tp + tbs + ts tos ¼ tp + tss + ts tod ¼ tp + tds + ts

(8.5)

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8. Calculation methods for carrying capacity

where tp, ts—the occupancy times of arrival and departure tracks for train receiving and dispatching respectively, in min; tps, tbs, tss, tds—the dwell times of the corresponding passenger trains on the arrival and departure tracks respectively, each of which is determined according to the procedure of technical operations for the train, in min. The calculation formula for the carrying capacity of arrival and departure tracks will be obtained by substituting αf into Eq. (8.2) to simplify it as: Np ¼

0:6819  0:2236αp  0:2602αb to Mp ð1440ts Þ  0:000887

(8.6)

4. Direct calculation method The basic principle of the direct calculation method: directly calculating the carrying capacity of a facility or a piece of equipment by calculating the ratio of the average time of each train occupying the facility or equipment to the working time that the facility or equipment can provide in 1 day and night. Eq. (8.7) is used for the direct calculation method:   1440 1  αf N¼ (8.7) tao where N—the carrying capacity of a facility or a piece of equipment at station, in trains; tao—the average time of a train occupying the facility or equipment. 5. Graphical method Based on queuing theory, the graphical method fully considers the coordination relationship between the station and lines connected and the operations of each component inside the station, and solves by taking all technical facilities as a unified whole. The graphical method can realize the coupling coordination between facilities and equipment, and avoid operation interference and reduce the idle time of equipment capacity to the greatest extent. However, the plotting and calculation involved in the graphical method require a lot of manpower and material resources, and it is difficult to adjust the graph.

8.2 Calculation methods for carrying capacity of high-speed railways

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8.2.2 Calculation methods for district carrying capacity .

The district carrying capacity is calculated in passenger flow section. The calculation methods include the coefficient removal method, average minimum train interval calculation method, computer-aided graphical method, and simulation method. 1. Coefficient removal method The coefficient removal method follows the traditional method for the carrying capacity of the nonparallel timetable graph. It is a static deterministic calculation method used under the conditions of “train operation as per the timetable,” good conditions of equipment and facilities, and no delay in operation. Based on the consumption capability of a train, the equivalent relationship between other trains and the train in capacity consumption is determined. This is called coefficient removal. Based on this, the theoretical value of district carrying capacity is determined by normalizing the capacity consumption of different types of trains to the number of standard trains. For high-speed railway, the district through the passenger train with the highest speed is usually taken as the standard train. To determine the coefficient removal of the capacity of other trains relative to high-speed trains, it is also necessary to consider the difference between the capacity for long-distance train lines and that for short-distance train lines. Therefore, the coefficient removal for different trains is determined separately in each passenger flow section. Therefore, the steps of the coefficient removal method are as follows: (1) Calculating the carrying capacity of the parallel timetable graph for high-speed trains; (2) Calculating the carrying capacity of the nonparallel timetable graph for high-speed trains; (3) Calculating the carrying capacity of the nonparallel timetable graph for the high-speed railway with the mixed operation of various passenger trains. 2. Average minimum train interval method The basic principle of average minimum train interval method is the theory of train delay propagation. During train operation, the service time (arrival time, departure time, and passing time) of a train at each station is usually not completely consistent with that given in the timetable graph, but fluctuates within a certain range, which will influence other trains and spread among trains. In order to suppress and alleviate the train delay propagation, the buffer time of the timetable graph shall be reserved reasonably when depicting the timetable graph. The steps of the average minimum train interval method are as follows:

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(1) Dividing the timetable graph into different periods, such as prime period, peak period, and off-peak period, according to the difference in train operation density in a day, (2) Determining the number of types of the train sets according to the running train set composed of adjacent trains in the same direction or opposite direction on the timetable graph and the train type groups formed by merging and sorting the train types; calculate the minimum interval and frequency of trains in each type of train set according to the running interval, and the ratio of the total time of all trains occupying the section to the total number of trains is the average minimum train interval. On this basis, the necessary average buffer time of the timetable graph is determined based on experience; (3) Calculating the district carrying capacity in different periods by Eq. (8.8), and the sum of the carrying capacities is the all-day district carrying capacity. L¼

T I+r

(8.8)

where L—the length of the period; I—the average minimum train interval during the period; r—the necessary average buffer time of timetable graph during the period. 3. Simulation method The simulation method refers to using computer technology to simulate the procedure of train operation in districts, and calculating the carrying capacity under different operation conditions by changing the simulation conditions and parameters. There have been studies on this subject in some foreign countries for a long time, and some achievements have been mad, such as RailSys jointly developed by the University of Hannover and German Railway Management Consulting Company, and Opentrack from Swiss Federal Institute.

8.3 Analysis on factors influencing carrying capacity of high-speed railway 8.3.1 Facilities and equipment 1. Station topology and throat length The station topology will affect the process of a train following an adjacent train. Minimizing the number of intrusion insulation joints by

8.3 Analysis on factors influencing carrying capacity of high-speed railway

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arranging track circuits and interlocking turnouts reasonably helps shorten the headway and improve the carrying capacity. The station throats are the unavoidable places for all arrival, departure, and passing trains. Yards of large and medium-sized high-speed railway stations generally are characterized by a large number of arrival and departure tracks and complex, long throats. Restricted by the diverging speed permitted on turnout, arrival and departure trains operate at low speeds in the station throat. The longer the station throat is, the longer time it is occupied by the preceding train, resulting in larger headway and lower carrying capacity. 2. Length of block section The length of a block section mainly affects the operating duration in which trains occupy resources such as track circuits. As the block section is extended, the operating duration is prolonged, which will increase the headway and reduce the carrying capacity. 3. Type and layout of turnouts Restricted by the type and layout of turnouts, the diverging speed permitted on turnout and the allowable passing speed of the main track have a direct bearing on the operation process of trains in a station. Arrival trains need to decelerate in advance to the diverging speed permitted on turnouts before they pull into stations, maintain this speed through the station throat, and come to a complete stop on the arrival and departure tracks. Departure trains accelerate from standstill to the diverging speed permitted on turnouts and leave the station at this speed. Similarly, if the speed of trains over sections exceeds the allowable passing speed of the main track at stations, the operation process of passing trains in stations is restricted by the allowable passing speed of the main track. Passing trains need to decelerate in advance to the allowable passing speed of the main track before they pull into stations, and pass through the station at this speed. The boost in the diverging speed permitted on turnouts and allowable passing speed of the main track will increase the braking distance, to a small extent for arrival and departure trains as they operate at low speeds in stations, and shorten the operating duration because trains can cease occupancy of resources such as track circuits and drive out of the station throat sooner. 4. Signal, interlocking, and block equipment of stations Improving signal, interlocking, and block equipment of stations helps shorten the headway. With respect to signal, for example, the headway will extend if the routing operation and additional operations like sending movement authority information take too long. CTCS-2 and CTCS-3 train control systems differ in the way they transmit the movement authority and the duration in which their CTC handles departure, arrival, and

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passing operations for and sends the movement authority information to the trains. CTCS-3 takes longer to transmit signals, and this is an important factor that affects the carrying capacity. The headway closely relates to the train’s occupancy of resources such as track circuits as they travel, and it is an important technical parameter for the carrying capacity. Relevant influencing factors include the horizontal and longitudinal sections and neutral zones of lines, speed control mode curve and information transmission time of train control systems, traction and braking performance of EMUs, restricted operating speed and the operation sequence of trains, length of the block section, the station topology and length of the station throat, train route, route setting and release times, station route setting and release rules. As the headway decreases, adjacent trains are able to follow more closely, bringing a larger carrying capacity. 5. Traction and braking performance of EMUs Various models of EMUs differ in traction and braking performance. With four common models of CRH1, CRH2, CRH3, and CRH380B, for example, the traction distance required for accelerating different models from standstill to varying speeds is shown in Fig. 8.4. The traction performance of EMUs mainly affects the operating duration in which trains occupy resources such as track circuits. The higher the traction performance, the shorter the traction distance required to accelerate trains to a certain speed, and the sooner trains reach a high speed, which helps shorten the headway and improve the carrying capacity. The braking performance of EMUs mainly affects the braking distance. According to the distance-to-go/continuous speed control mode curve of train control

FIG. 8.4 Traction distance of different EMUs to reach different operating speed.

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systems, as the braking performance of EMUs improves, the braking distance required for a train at a certain speed to stop is shortened, which will shrink the space interval between adjacent trains and help cut their tracking operation interval and enhance the carrying capacity.

8.3.2 Train operation organization 1. Train operation district Vertical rectangle windows are extensively applied on high-speed railways, and as the train operation district elongates, the train operation time zones get increasingly narrower, and “triangle areas” become increasingly wider, which will lead to a reduction in the carrying capacity. 2. Speed difference and proportion of trains Most high-speed railways operate different speed trains in a mixed manner. In the timetable graph, the larger the speed difference is, the smaller the carrying capacity will be since there is more unserviceable space before and after the paths of trains with lower speeds. Meanwhile, the carrying capacity is larger when trains of a single type are operated, and it is smaller when different speed trains in operation are similar in their respective proportion. 3. Stop schedule plan of trains As far as resources such as track circuits are concerned, additional occupancy time will elapse when a train stops at a station, including the dwell time, train starting additional time, and additional time for train stopping. The more often a train stops and the longer the dwell time, the longer the duration in which the train occupies the resources, and the lower the carrying capacity. How the stop schedule plans of adjacent trains combine also affects the carrying capacity. If they stop in a staggered manner (i.e., the preceding train stops at the farther station and the following train stops at the nearer station), the space before and after the train path can be fully utilized to enhance the carrying capacity. 4. Speed control mode curve and information transmission time of train control systems When adjacent trains are in train following, their space interval must be greater than the braking distance of the following train braking to stop from the current operating speed. The braking distance is determined by the distance-to-go/continuous speed control mode curve of train control systems. The train speed over sections is high on high-speed railways, and this results in a long braking distance, which is an important factor influencing the headway. The headway also depends on the information

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transmission time between different equipment of the train control system. Therefore, it helps shorten the headway and enhance the carrying capacity if the generation strategy is improved for the distance-to-go/continuous speed control mode curve and the information transmission efficiency is increased. 5. Train speed over sections The train speed over sections depends on the infrastructure and the EMU itself and bears on the braking distance of trains and their operating duration in track circuits and other resources. Increasing the train speed over sections will result in an increased braking distance and a larger space interval between adjacent trains, and on the other hand, trains will cease occupying track circuits and other resources sooner, meaning a shorter operating duration. Generally, the train speed over sections is high on high-speed railways, resulting in a long braking distance. Moreover, the braking distance has a greater effect on the headway than the operating duration does. Thus, as the train speed over sections increases, the headway will extend, which will, in turn, reduce the carrying capacity. 6. Train operation sequence If adjacent trains are heterogeneous (e.g., they differ in speed over sections and whether they stop at a station), their headway will change if the train operation sequence varies. When the preceding train has a high speed and the following train has a low speed, for example, it is certain that the headway will be affected by any change in their operation sequence. As shown in Fig. 8.5, the carrying capacity in drawing method 2 is larger than that in drawing method 1.

FIG. 8.5 Effect of train operation sequence on carrying capacity.

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8.3.3 Station operation organization 1. Station route setting and release rules By changing the station route setting rules, it is helpful to reduce the headway and enhance the carrying capacity. The station route setting and release rules affect the train following process of adjacent trains. The current station route setting rules provide that before the interlocking system establishes a route, all track circuits on the route must be clear, the turnouts on the route are in the correct position, and no conflicting route is established. In the same route protected by the signal, it is not allowed to operate two or more trains simultaneously. In addition, the segmentation release mode is widely applied for routes of high-speed railway stations. In this mode, tracks circuits are released segment by segment as the train travels. 2. Utilization of tracks Tracks at high-speed railway stations are utilized in three ways, i.e., balanced utilization of tracks, compact utilization of tracks, and utilization of tracks with minimal cross operation interference. In balanced utilization of tracks, each track receives and dispatches trains in an equal or roughly equal number, and the total occupancy time is close. In this way, the carrying capacity of the station throat and the arrival and departure tracks is utilized in a balanced manner, but it tends to cause cross-interference of train routes and increase the headway. In compact utilization of tracks, the idle time of each track between receiving and dispatching subsequent trains is minimized and distributed evenly to increase its utilization ratio and in turn the station carrying capacity. In the utilization of tracks with minimal cross operation interference, the track with minimal conflicting routes is prioritized for receiving and dispatching trains, so as to reduce interference to the operation of subsequent trains and enhance the carrying capacity of arrival and departure tracks and the station throat.

8.3.4 Other factors 1. Horizontal and longitudinal sections and traction districts of lines According to the theory on train traction calculation, the horizontal and longitudinal sections and neutral zones of lines are among the calculation factors vital for the train operation curve, and they mainly influence the operating duration of trains in track circuits and other resources. Within the line range of adjacent stations, if there is any long steep downgrade in the arrival direction, the train will start braking earlier and the braking process will become longer; if there is any long steep upgrade or small radius curve in the departure direction, the train operation resistance will

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be increased and the traction process will become longer. In the neutral zone, trains coast without any tractive or braking effort. If a train is under negative stress in the neutral zone, its speed will decrease; if a train is under positive stress in the neutral zone (i.e., the neutral zone is located on a downgrade), its speed will increase. If a train exceeds the restricted operating speed, it needs to decelerate in advance of entering the neutral zone. As the operating duration prolongs, the headway will be lengthened, which means a reduction in the carrying capacity. 2. Passenger service rules High-speed railways mainly serve passengers, and thus they have a much higher requirement for service quality than existing railways. The service quality is mainly demonstrated by train punctuality, speed, and convenience. It is obvious that the guiding thought for train operation organization on existing railways no longer applies. To be specific, it fully taps the potential of those lines, makes the most use of their carrying capacity, but gives little consideration to transport quality indicators such as punctuality and passenger travel time. Research has shown that when the quality of train operation service provided by high-speed railways can no longer sweeten the deal for passengers, some transport capacity resources will still be wasted even if the carrying capacity is not utilized to the load criterion of the design capacity. This makes ensuring the transport service quality and reasonably exploiting the railway carrying capacity vital. Different levels of operation service result from different types and combination modes of trains in operation, which also lead to unequal carrying capacity between track districts. Therefore, before the detailed train operation scheme and the plan for depicting the timetable graph are formulated, it is necessary to analyze the carrying capacity of the research district on passenger dedicated railways corresponding to different train combinations and operation proportions while ensuring high operation service quality, so as to establish reasonable passenger service rules.

References [1] H. Yang, Railway Transport Organization, China Railway Publishing House, Beijing, 2006. [2] B.T. Duan, Discussion on the calculation of carrying capacity of high-speed railway station, Railw. Stand. Des. 59 (11) (2015) 43–48. [3] Y. Lin, Related Technologies for Improving the Carrying Capacity of High-Speed Railway, Southwest Jiaotong University, 2018.

C H A P T E R

9 Mechanism of enhancing the carrying capacity of high-speed railway by precise headway in station 9.1 Concept and type of headway in station on high-speed railways The headway in station is the minimum time required for handling the arrival, departure or passing operation between two trains at a station. When the headway in a high-speed railway station is determined, the relevant regulations and the standard times for station technical operations shall be complied with to ensure the train operation safety and utilize the district carrying capacity efficiently. Traditionally, the headways in station include the successive arrival headway, the crossing headway, the successive departure headway, the departure-arrival headway, and the arrival-departure headway. Their values relate to the operating methods for station signals and turnouts, the blocking methods for the adjacent sections of the station, the station type, plan and profile of tracks adjacent to the station, the locomotive types, the train masses and lengths, and other factors. Prior to depicting the timetable graph of a station, all the headways shall be determined according to the specific conditions. In fact, the headways in station can also be classified according to the train operation state and direction. The operation state refers to the arrival, departure, or passing operation handled at the station. Restricted by the diverging speed permitted on turnouts and the allowable passing speed of the main track, trains in different operation states have different operation procedures in the station and different occupancy times in the

Theory and Technology for Improving High-Speed Railway Transportation Capacity https://doi.org/10.1016/B978-0-323-99700-3.00013-X

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station throat. In addition, different types of technical operations handled at the station need different standard times. The headway in station thus takes different values when adjacent trains show different combinations of operation states. According to the operation state combination of adjacent trains, the headway in station is classified into arrival-arrival, departuredeparture, passing-passing, arrival-passing, passing-arrival, departurepassing, passing-departure, arrival-departure, and departure-arrival headways.

9.1.1 Arrival headway The arrival headway refers to the minimum duration, when two opposite trains meet at a station in a single-track district, between a train’s arrival at the station in a direction and the other train’s arrival at or passing the station in the other direction, as shown in Fig. 9.1. To increase the travel speed of trains, one of the two crossing trains shall in principle run past the station without stopping, and therefore the arrival headway with one train stopping and the other passing by is commonly adopted in the timetable graph, except when both up and down trains need to stop at the same station for operation. In a double-track district, no arrival headway is needed. According to the train operation state and direction, the arrival headways can be further classified into the opposite arrival-passing headway and the opposite arrival headway.

9.1.2 Crossing headway The crossing headway refers to the minimum duration, in a single-track district, between a train’s arrival at or passing a station and another opposite train’s departure to the same section, as shown in Fig. 9.2. In a doubletrack district, no crossing headway is needed. According to the train operation state, the crossing headways can be further classified into the opposite passing-departure headway and the opposite arrival-departure headway.

FIG. 9.1 Diagram of headway of two arrivals.

9.2 Existing calculation methods for headway in station

FIG. 9.2

285

Diagram of headway for crossing of two opposite trains.

FIG. 9.3 Diagram of arrival-departure headway and departure-arrival headway in the same direction.

9.1.3 Arrival-departure headway and departure-arrival headway The arrival-departure headway refers to the minimum duration, in a single- or double-track district, between a train’s arrival at a station and another train’s departure in the same direction. The departure-arrival headway refers to the minimum duration, also in a single- or double-track district, between a train’s departure from a station and another train’s arrival from the same direction. Fig 9.3 shows the representations of these two headways in the graph.

9.1.4 Opposite passing headway It refers to the minimum duration between two opposite trains’ passing a station separating a double-track section and a single-track section at different times. According to the train operation state, the headway between two passing trains in opposite directions is the passing-passing headway of opposite trains.

9.2 Existing calculation methods for headway in station 9.2.1 Calculation method for arrival headway The arrival headway is determined according to the following conditions: (1) The home signal can be cleared for the opposite train only after the first train arrives at the station and the receiving route is prepared.

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FIG. 9.4 Diagram of train position with a cleared home signal and headway of two arrivals.

(2) When the home signal is cleared, the distance of the tip of the train to the home signal shall equal the sum of one braking distance plus the travel distance within the period for the driver to confirm the signal’s aspect, as shown in Fig. 9.4. The arrival headway consists of tw, the time required for handling necessary operations for the first train arriving at the station, te required for the opposite train to travel over the distance Le from the home signal to the centerline of the station. The following equation is hereby obtained τa ¼ tw + te ¼ tw + 0:06∗ Le =ve ¼ tw + 0:06∗ ð0:5lt + la + lb + le Þ=ve ð min Þ (9.1) where lt—the train length, in m; la—the train running distance until the driver confirms the home signal’s aspect, in m; lb—the train braking distance, in m; le—the distance from the home signal to the station centerline, m; ve—the average train speed from the home signal to the station centerline, km/h. Since both le and ve vary at different ends of a station, the arrival headway must be determined separately for up and down trains at each station.

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The time required for a station to handle necessary operations shall be determined according to the signal, interlock, and block equipment conditions and operation contents.

9.2.2 Calculation method for crossing headway The crossing headway is the time required for handling necessary operations from the time the station staff detects the arrival or passage of a train to the time the other train is dispatched to the same section. It is determined according to the signal, interlock, and block equipment conditions and operation contents at each station.

9.2.3 Calculation method for arrival-departure headway and departure-arrival headway For all stations where simultaneous reception and departure of trains in the same direction is prohibited, the arrival-departure headway and departure-arrival headway must be determined. The following two conditions must be complied with in determining these two headways: (1) When arrival and departure of trains in the same direction are handled, the outgoing train can only depart after all of the incoming trains has arrived and stopped in advance of the fouling post. (2) When departure and arrival of trains in the same direction are handled, the train to pull in must wait at the position lb + la in rear of the home signal at the station until the first train has run past the last departure turnout on the departure route completely and the station has handled all relevant operations. Based on the above, the arrival-departure headway is the time required for handling necessary operations after the station staff detects the arrival of the first train and before the other train is dispatched in the same direction, while the departure-arrival headway, as shown in Fig. 9.5, consists of three parts, i.e., tl, the time for the outgoing train to travel over the distance Ll, tw, the p time for the station to handle necessary operations, and te, the time for the incoming train in the same direction to travel over the distance Le. The following equation is thus obtained: τsa ¼ tl + tw + te ð min Þ

(9.2)

As can be seen from Fig. 9.5, tl ¼ 0:06ðll + 0:5lt Þ=vl ð min Þ

(9.3)

te ¼ 0:06ð0:5lt + la + lb + le Þ=ve ð min Þ

(9.4)

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9. Mechanism of enhancing the carrying capacity

FIG. 9.5 Composition of headway between departure and arrival in the same direction.

Therefore, the calculation formula for the departure-arrival headway can also be written as: τsa ¼ tw + 0:06∗ ððll + 0:5lt Þ=vl + ð0:5lt + la + lb + le Þ=ve Þ ð min Þ

(9.5)

where ll—the distance from the station centerline to the outermost turnout on the departure route, in m; vl—the average train speed from departing over the distance of ll, in km/h.

9.2.4 Calculation method for opposite passing headway As shown in Fig. 9.6, the opposite passing headway also consists of tw and te. All of the values of the above headways in station relate to the train speed and length, and thus they shall be calculated separately.

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FIG. 9.6 Composition of headway between two passing trains in opposite directions over single- and double-track districts.

9.3 Precise calculation of headway in station based on time-space graph of train tracking operation 9.3.1 Time-space graph of train tracking operation A reasonable description of the following process of the train in sections and stations is the basis for calculating the headway in station. For this purpose, the quasi-moving block mode is widely used for high-speed railways. In this mode, the line is divided into several track circuits, so the transport capacity resource is the line area with a certain length. Based on the high-speed railway operation rules, in order to analyze the temporal and spatial occupation of transport capacity resources by high-speed railway trains during the operation in sections and stations, on the one hand, this chapter proposes the concept of the train occupation unit as follows from the perspective of the spatial dimension. The train occupation unit is the minimum line unit occupied by the train during the operation on the line. In a section, the occupation by the train is checked by the track circuit, and the train occupation unit in the section is the track circuit; in a station, based on the comprehensive consideration of the layout of the track circuit, linkage turnout and invasion insulation section of the train route, the train occupation unit is the minimum block in a station.

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FIG. 9.7 Constitution of occupation time in one occupation unit.

On the other hand, from the perspective of time dimension, the time for the train to occupy the transport capacity resources includes information transmission time, operator response time, the time required for the train to pass the braking distance, and running time, this chapter proposes the time for the train to occupy the single train occupation unit, including preparation time, reaction time, braking time (or continuous time), running time, clearing time and closing time, as shown in Fig. 9.7; all occupation time can be obtained through the train operation curve. During train tracking operation, it is necessary to identify the conflict area of adjacent trains on the running path and eliminate the conflict by limiting at most one train to run in the conflict area. According to the train operation organization rules, the station route setting and release rules, the train operation conflict area in the section is defined as follows: one train operation conflict area is a block section, and there may be multiple track circuits. The train operation conflict area in the station is the route conflict area, and the route conflict area includes at least one minimum block section in a station according to the route setting rules. On the basis of defining the train occupation unit, occupation time, and operation conflict area, the time-space graph can be used to describe the process of the train tracking operation in the section and station [1]. 9.3.1.1 Time-space graph of train tracking operation in section In case of the train tracking in a section, if there are two or more track circuits in one block section at the same time, the track circuits in this block section start to be occupied at the same time; therefore, for all track circuits in the same block section, the starting time of the train occupation time is

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291

the same. Each track circuit has the function of checking the occupation by the train, and the track circuits occupied in the block section are released one by one by the train. Therefore, all track circuits in the same block section vary in the ending time of the train occupation time. Only after the preceding train releases the occupation of all track circuits in a block section can the block section be occupied by the following train. Based on the above train operation rules in a section, the section track circuit is taken as the basic unit in space, and the train occupation time is quantified in time. The occupation of transport capacity resources by adjacent trains during the following process in a section can be described by using the time-space graph shown in Fig. 9.8. 9.3.1.2 Time-space graph of train tracking operation in station Before the train route is established, all track circuits on the route must be clear; after the train route is set, all the minimum block sections in the station on the route are occupied by the train at the same time, and no other train is allowed to occupy them. Therefore, in terms of all the minimum block sections on the same route, the starting time of the train occupation time is the same. With the operation of the train, the track circuits are released one by one; therefore, all the minimum block sections on the same route vary in the ending time of the train occupation time. Based on the above train operation rules in a station, the minimum block section is taken as the basic unit in space, and the train occupation time is quantified in time. The occupation of transport capacity resources by adjacent trains during the following process in a station can be described by using the time-space graph. 1. Adjacent arrival trains The train arrival time is the time when the train comes to a complete stop on the arrival and departure tracks. For the adjacent arrival trains, the following process of the train in a station is shown in Fig. 9.9 (block sections 1–5 in the Fig. 9.9 represents the minimum block sections in station). The route conflict area includes the minimum block sections 1, 2, and 3. After the preceding train ceases occupying the minimum block section 3, the establishment of the receiving route for the following train can be started. In the minimum block section qwc, d (the minimum block sections 4 and 5 in Fig. 9.9), where the district without turnout on the arrival and departure track is located, the train arrival time is the ending time of the running time. In the composition of the train occupation time, the train brakes and stops in the minimum block section qwc, d, so the clearing time is 0. 2. Adjacent departure trains The train departure time is the time when the train starts and accelerates on the arrival and departure tracks. For the adjacent departure trains, the following process of the train in a station is shown in Fig. 9.10 (block

FIG. 9.8 Temporal-spatial graph of tracking process for a pair of trains in a section.

FIG. 9.9 Temporal-spatial diagram of tracking process for a pair of arrival trains in a station.

FIG. 9.10 Temporal-spatial diagram of tracking process for a pair of departure trains in a station.

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sections 1–3 in the Fig. 9.10 represents the minimum block sections in station). The route conflict area includes the minimum block sections 1, 2, 3, and the first departure block section. After the preceding train ceases occupying the first departure block section, the establishment of the departure route for the following train can be started. In the minimum block section qwc, d (the minimum block section 1 in Fig. 9.10) where the district without turnout on the arrival and departure track is located, the train departure time is the starting time of the running time. In the composition of the train occupation time, the train starts traction acceleration from a standstill in the minimum block section in station qwc, d, so the braking time is 0. 3. Adjacent passing trains For adjacent passing trains, the following process of the train in a station is shown in Fig. 9.11; the passing time of the train is the time when the train enters the block section in the station where the main track IG or IIG is located. In Fig. 9.11 (block sections 1–5 in the Fig. 9.11 represents the minimum block sections in station), the route conflict area includes the minimum block sections 1–5 and the first departure block section. After the preceding train ceases occupying the first departure block section, the establishment of the passing route for the following train can be started. In the minimum block section qwc, z (the minimum block section 3 in Fig. 9.11) where the district without turnout in the middle of the main track of the station is located, the passing time is the starting time of the running time. 4. Adjacent arrival and passing trains For the adjacent arrival and passing trains, the following process of the train in a station is shown in Fig. 9.12 (block sections 1–7 in the Fig. 9.12 represents the minimum block sections in station). The route conflict area includes the minimum block sections 1 and 2. After the preceding train ceases occupying the minimum block section 2, the establishment of the passing route for the following train can be started. 5. Adjacent passing and arrival trains For the adjacent passing and arrival trains, the following process of the train in a station is shown in Fig. 9.13 (block sections 1–7 in the Fig. 9.13 represents the minimum block sections in station). The route conflict area includes the minimum block sections 1 and 2. After the preceding train ceases occupying the minimum block section 2, the establishment of the receiving route for the following train can be started. 6. Adjacent departure and passing trains For the adjacent departure and passing trains, the following process of the train in a station is shown in Fig. 9.14 (block sections 1–6 in the Fig. 9.14

FIG. 9.11 Temporal-spatial diagram of tracking process for a pair of passing trains in a station.

FIG. 9.12 Temporal-spatial diagram of tracking process for a departure train and a passing train in a station.

FIG. 9.13 Temporal-spatial diagram of tracking process for a passing train and a departure train in a station.

FIG. 9.14 Temporal-spatial diagram of tracking process for a departure train and a passing train in a station.

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represents the minimum block sections in station). The route conflict area includes the minimum block sections 5 and 6, and the first departure block section. After the preceding train ceases occupying the first departure block section, the establishment of the passing route for the following train can be started. 7. Adjacent passing and departure trains For the adjacent passing and departure trains, the following process of the train in a station is shown in Fig. 9.15 (block sections 1–6 in the Fig. 9.15 represents the minimum block sections in station). The route conflict area includes the minimum block sections 5 and 6, and the first departure block section. After the preceding train ceases occupying the first departure block section, the establishment of the departure route for the following train can be started. 8. Adjacent arrival and departure trains For the adjacent arrival and departure trains, the following process of the train in a station is shown in Fig. 9.16 (block sections 1–6 in the Fig. 9.16 represents the minimum block sections in station). The route conflict area includes block sections 1, 2, and 3. After the preceding train ceases occupying block section 3, the establishment of the departure route for the following train can be started. 9. Adjacent departure and arrival trains For the adjacent departure and arrival trains, the following process of the train in a station is shown in Fig. 9.17 (block sections 1–5 in the Fig. 9.17 represents the minimum block sections in station). The route conflict area includes the minimum block sections 2 and 3. After the preceding train ceases occupying the minimum block section 2, the establishment of the receiving route for the following train can be started.

9.3.2 Classification and calculation characteristics of headway in station The headway in station restricts the time of arrival, departure, or passing of two trains with route conflicts in space, and eliminates the operation conflicts between such trains by means of time reconciliation. To accurately and reasonably calculate and analyze the headway in high-speed railway stations, the headways need to be subdivided into types, and subsequently, calculation methods based on the time-space graph of train tracking operation shall be proposed. Such methods shall take a station and its adjacent sections as the research line range, give consideration to the operation process, and aim at minimizing the headway between

FIG. 9.15 Temporal-spatial diagram of tracking process for a passing train and a departure train in a station.

FIG. 9.16 Temporal-spatial diagram of tracking process for an arrival train and a departure train in a station.

FIG. 9.17 Temporal-spatial diagram of tracking process for a departure train and an arrival train in a station.

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9. Mechanism of enhancing the carrying capacity

the time of arrival, departure, or passing of adjacent trains on the condition of avoiding train operation conflicts. 9.3.2.1 Types of headway in station 1. Classification standard for headway in station Headway in station is the minimum interval between the time of arrival, departure, or passing of two adjacent trains at a station. According to the operation state, route type and operation direction of adjacent trains, headways in station can be classified into the following types: (1) Operation state combination of adjacent trains The operation state refers to the arrival, departure, or passing operation handled at the station. Restricted by the diverging speed permitted on turnouts and the allowable passing speed of the main track, trains in different operation states vary in time of their occupying the station throat, and the time for the station to handle various technical operations. For this reason, the headways in station are classified into nine types corresponding to different combinations of operation states of adjacent trains, i.e., arrivalarrival, departure-departure, passing-passing, arrival-passing, passingarrival, departure-passing, passing-departure, arrival-departure, and departure-arrival headway. (2) Route combination of adjacent trains The headway in station is closely related to the routes of adjacent trains in the station, and train routes of different combinations cross or conflict by a different length of track sections, resulting in the difference in headway between adjacent trains. At present, many trains turn back immediately in large and medium stations of high-speed railways, and their routes are set in two forms—“forward reception and reverse departure” and “reverse reception and forward departure.” In the first form, the receiving route does not cut the station throat, and the departure route cuts the throat, as shown in Fig. 9.18A, while in the second form, things go the other way around, as shown in Fig. 9.18B. A train route that cuts the throats usually crosses other train routes, resulting in conflict. For easier analysis of the minimum headway between turn-back trains and other trains, the train routes can be divided into categories, namely I, II, and III depending on whether they cut the throat. Category I train route does not

FIG. 9.18

Train route arrangement of turn-back trains.

305

9.3 Precise calculation of headway in station

cut the throat, Category II train route cuts the throat, and Category III train route is for passing train. Based on the train route combination of adjacent trains, there are six types of headway in station, namely I + I, II + II, III + III, I + II, I + III, and II + III. (3) Operation direction combination of adjacent trains A train route that cuts the throat will conflict with both the routes of the up and down trains, and thus based on the directions of adjacent trains, there are two types of headway in station, namely in the same direction and in opposite directions. 2. Analysis of route conflict between adjacent trains Train operation will consume the transport capacity as resource in terms of time and space, and the operation conflicts between adjacent trains in a station can be eliminated in two ways: (1) spatial reconciliation, i.e., setting parallel routes for them to avoid crossing or overlapping; and (2) temporal reconciliation, i.e., defining the minimum headway between the time (the constraint of the headway in the station) of arrival, departure, or passing of adjacent trains whose routes cross or overlap, which means conflict with each other. Thus, it can be seen that headway is used to deal with adjacent trains whose routes conflict. Based on the operation state of adjacent trains, the train route combinations with possible operation conflicts may be sifted out by further taking into consideration the type and direction of train routes, as shown in Table 9.1. TABLE 9.1 Route combinations with possible operation conflicts. Operation state of adjacent trains

Train operation direction

Train route combination

Existence of route conflict

Arrival-arrival

Same direction

I+I

Yes

Arrival-arrival

Same direction

II + II

Yes

Arrival-arrival

Same direction

I + II

Yes

Arrival-arrival

Opposite direction

–

No

Departure-departure

Same direction

I+I

Yes

Departure-departure

Same direction

II + II

Yes

Departure-departure

Same direction

I + II

Yes

Departure-departure

Opposite direction

–

No

Passing-passing

Same direction

III + III

Yes

Passing-passing

Opposite direction

–

No Continued

TABLE 9.1 Route combinations with possible operation conflicts—cont’d Operation state of adjacent trains

Train operation direction

Train route combination

Existence of route conflict

Arrival-passing

Same direction

I + III

Yes

Arrival-passing

Same direction

II + III

Yes

Arrival-passing

Opposite direction

I + III

No

Arrival-passing

Opposite direction

II + III

Yes

Passing-arrival

Same direction

I + III

Yes

Passing-arrival

Same direction

II + III

Yes

Passing-arrival

Opposite direction

I + III

No

Passing-arrival

Opposite direction

II + III

Yes

Departure-passing

Same direction

I + III

Yes

Departure-passing

Same direction

II + III

Yes

Departure-passing

Opposite direction

I + III

No

Departure-passing

Opposite direction

II + III

Yes

Passing-departure

Same direction

I + III

Yes

Passing-departure

Same direction

II + III

Yes

Passing-departure

Opposite direction

I + III

No

Passing-departure

Opposite direction

II + III

Yes

Arrival-departure

Same direction

–

No

Arrival-departure

Opposite direction

I+I

No

Arrival-departure

Opposite direction

II + II

Yes

Arrival-departure

Opposite direction

I + II

Yes

Departure-arrival

Same direction

–

No

Departure-arrival

Opposite direction

I+I

No

Departure-arrival

Opposite direction

II + II

Yes

Departure-arrival

Opposite direction

I + II

Yes

9.3 Precise calculation of headway in station

307

(1) Two arrival trains in the same direction The train route combination might be I + I, II + II, or I + II, in any of which, the routes of the adjacent trains cross or overlap. Assuming that both of the adjacent trains run in the down direction, Figs. 9.19–9.21 respectively illustrate the route conflicts in the case of I + I, II + II, and I + II. In Fig. 9.19, the preceding and following trains are received by Track 5G and Track 3G, respectively, resulting in possible operation conflict in the station throat on the side of the home signal X in the down direction. In Fig. 9.20, the preceding and following trains are received by Track 4G and Track 6G, respectively, in a “reverse reception” manner, resulting in possible operation conflict in the station throat on the side of the home signal X in the down direction and the station throat on the side of the reverse home signal XF in the down direction. In Fig. 9.21, the preceding train is received by Track 5G, and the following train is received by Track 6G in a “reverse reception” manner, resulting in possible operation conflict in the station throat on the side of the home signal X in the down direction.

FIG. 9.19 Train routes of two arrival trains in the same direction in train route combination I + I.

FIG. 9.20 Train routes of two arrival trains in the same direction in train route combination II + II.

FIG. 9.21 Train routes of two arrival trains in the same direction in train route combination I + II.

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9. Mechanism of enhancing the carrying capacity

(2) Two arrival trains in opposite directions When two trains enter a station through the throats at two ends respectively and will not be received by the same track, their receiving routes do not cross or overlap, and it is unnecessary to define the minimum headway between their arrival times. (3) Two departure trains in the same direction The train route combination might be I + I, I + II, or I + II, in any of which, the routes of the adjacent trains cross or overlap. Assuming that both of the adjacent trains run in the down direction, Figs. 9.22–9.24 respectively illustrate the route conflicts in the case of I + I, II + II, and I + II. In Fig. 9.22, the preceding and following trains depart via Track 5G and Track 3G, respectively, resulting in possible operation conflict in the station throat on the side of the reverse home signal SF in the up direction. In Fig. 9.23, the preceding and following trains depart via Track 4G and Track 6G, respectively in a “reverse departure” manner, resulting in possible operation

FIG. 9.22 Train routes of two departure trains in the same direction in train route combination I + I.

FIG. 9.23 Train routes of two departure trains in the same direction in train route combination II + II.

FIG. 9.24 Train routes of two departure trains in the same direction in train route combination I + II.

9.3 Precise calculation of headway in station

309

conflict in the station throat on the side of the home signal S in the up direction and the station throat on the side of the reverse home signal SF in the up direction. In Fig. 9.24, the preceding train departs via Track 5G, and the following train departs via Track 6G in a “reverse departure” manner, resulting in possible operation conflict in the station throat on the side of the reverse home signal SF in the up direction. (4) Two departure trains in opposite directions When two trains depart from the throats at both ends of a station respectively, their departure routes do not cross or overlap, and it is unnecessary to define the minimum headway between their departure times. (5) Two passing trains in the same direction The only train route combination is III + III, and their passing routes overlap. Assuming that both of the adjacent trains run in the down direction, Fig. 9.25 illustrates the conflict between adjacent passing routes in the case of III + III. The preceding and following trains pass through the station via Track IG, resulting in possible operation conflict in the station throat on the side of the home signal X in the down direction and the station throat on the side of the reverse home signal SF in the up direction. (6) Two passing trains in opposite directions When the passing routes of trains respectively in the up and down directions neither cross nor overlap, it is unnecessary to define the minimum headway between such passing trains. (7) An arrival train and a passing train in the same direction The train route combination might be I + III or II + III, in any of which, the routes of the adjacent trains cross or overlap. Assuming that both of the adjacent trains run in the down direction, Figs. 9.26 and 9.27 respectively illustrate the route conflicts in the case of I + III and II + III. In Fig. 9.26, the preceding train is received by Track 5G, and the following train passes through the station via Track IG, resulting in possible operation conflict in the station throat on the side of the home signal X in the down direction. In Fig. 9.27, the preceding train is received by Track 4G in a “reverse

FIG. 9.25 tion III + III.

Train routes of two passing trains in the same direction in train route combina-

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9. Mechanism of enhancing the carrying capacity

FIG. 9.26

Train routes of an arrival train and a passing train in the same direction in train route combination I + III.

FIG. 9.27

Train routes of an arrival train and a passing train in the same direction in train route combination II + III.

reception” manner, and the following train passes through the station via Track IG, resulting in possible operation conflict in the station throat on the side of the home signal X in the down direction. (8) An arrival train and a passing train in opposite directions The train route combination might be I + III or II + III, and the routes of the adjacent trains cross or overlap only in the case of II + III. Assuming that the two trains run in down and up directions respectively, Figs. 9.28 and 9.29 respectively illustrate the route conflicts in the case of I + III and II + III. In Fig. 9.28, the preceding train is received by Track 5G, and the following train passes through the station via Track IIG. The train routes neither cross nor overlap, and thus there is no operation conflict. In Fig. 9.29, the preceding train is received by Track 4G in a “reverse reception” manner, and the following train passes through the station via Track IIG, resulting in possible operation conflict in the station throat on the side of the reverse home signal XF in the down direction.

FIG. 9.28 Train routes of an arrival train and a passing train in opposite directions in train route combination I + III.

9.3 Precise calculation of headway in station

311

FIG. 9.29 Train routes of an arrival train and a passing train in opposite directions in train route combination II + III.

(9) A passing train and an arrival train in the same direction When adjacent trains successively pass through and arrive at a station in the same direction, the train route combination might be I + III or II + III, in any of which, the routes of the adjacent trains cross or overlap. Assuming that both of the adjacent trains run in the down direction, Figs. 9.30 and 9.31 respectively illustrate the route conflicts in the case of I +III and II + III. In Fig. 9.30, the preceding train passes through the station via Track IG, and the following train is received by Track 5G, resulting in possible operation conflict in the station throat on the side of the home signal X in the down direction. In Fig. 9.31, the preceding train passes through the station via Track IG, and the following train is received by Track 4G in a “reverse reception” manner, resulting in possible operation conflict in the station throat on the side of the home signal X in the down direction. (10) A passing train and an arrival train in opposite directions When adjacent trains successively pass through and arrive at a station in opposite directions, the train route combination might be I + III or II + III,

FIG. 9.30 Train routes of a passing train and an arrival train in the same direction in train route combination I + III.

FIG. 9.31 Train routes of a passing train and an arrival train in the same direction in train route combination II + III.

312

9. Mechanism of enhancing the carrying capacity

and the routes of the adjacent trains cross or overlap only in the case of II +III. Assuming that the two trains run in up and down directions respectively, Figs. 9.32 and 9.33 respectively illustrate the route conflicts in the case of I + III and II + III. In Fig. 9.32, the preceding train passes through the station via Track IIG, and the following train is received by Track 5G. The train routes neither cross nor overlap, and thus there is no operation conflict. In Fig. 9.33, the preceding train passes through the station via Track IIG, and the following train is received by Track 4G in a “reverse reception” manner, resulting in possible operation conflict in the station throat on the side of the reverse home signal XF in the down direction. (11) A departure train and a passing train in the same direction When adjacent trains successively depart from and pass through a station in the same direction, the train route combination might be I + III or II + III, in any of which, the routes of the adjacent trains cross or overlap. Assuming that both of the adjacent trains run in the down direction, Figs. 9.34 and 9.35 respectively illustrate the route conflicts in the case of I + III

FIG. 9.32 Train routes of a passing train and an arrival train in opposite directions in train route combination I + III.

FIG. 9.33 Train routes of a passing train and an arrival train in opposite directions in train route combination II + III.

FIG. 9.34

Train routes of a departure train and a passing train in the same direction in train route combination I + III.

9.3 Precise calculation of headway in station

313

FIG. 9.35

Train routes of a departure train and a passing train in the same direction in train route combination II + III.

and II + III. In Fig. 9.34, the preceding train departs from Track 5G, and the following train passes through the station via Track IG, resulting in possible operation conflict in the station throat on the side of the reverse home signal SF in the up direction. In Fig. 9.35, the preceding train departs from Track 4G in a “reverse departure” manner, and the following train passes through the station via Track IG, resulting in possible operation conflict in the station throat on the side of the reverse home signal SF in the up direction. (12) A departure train and a passing train in opposite directions When adjacent trains successively depart from and pass through a station in opposite directions, the train route combination might be I + III or II + III, and the routes of the adjacent trains cross or overlap only in the case of II + III. Assuming that the two trains run in down and up directions respectively, Figs. 9.36 and 9.37 respectively illustrate the route conflicts in the case of I + III and II + III. In Fig. 9.36, the preceding train departs via Track 5G, and the following train passes through the station

FIG. 9.36 Train routes of a departure train and a passing train in opposite directions in train route combination I + III.

FIG. 9.37 Train routes of a departure train and a passing train in opposite directions in train route combination II + III.

314

9. Mechanism of enhancing the carrying capacity

via Track IIG. The train routes neither cross nor overlap, and thus there is no operation conflict. In Fig. 9.37, the preceding train departs via Track 4G in a “reverse departure” manner, and the following train passes through the station via Track IIG, resulting in possible operation conflict in the station throat on the side of the home signal S in the up direction. (13) A passing train and a departure train in the same direction When adjacent trains successively pass through and depart from a station in the same direction, the train route combination might be I + III or II + III, in any of which, the routes of the adjacent trains cross or overlap. Assuming that both of the adjacent trains run in the down direction, Figs. 9.38 and 9.39 respectively illustrate the route conflicts in the case of I + III and II + III. In Fig. 9.38, the preceding train passes through the station via Track IG, and the following train departs via Track 5G, resulting in possible operation conflict in the station throat on the side of the reverse home signal SF in the up direction. In Fig. 9.39, the preceding train passes through the station via Track IG, and the following train departs via Track 6G in a “reverse departure” manner, resulting in possible operation conflict in the station throat on the side of the reverse home signal SF in the up direction. (14) A passing train and a departure train in opposite directions When adjacent trains successively pass through and depart from a station in opposite directions, the train route combination might be I + III or II + III, and the routes of the adjacent trains cross or overlap only in the case of II + III. Assuming that the two trains run in up and down directions respectively,

FIG. 9.38

Train routes of a passing train and a departure train in the same direction in train route combination I + III.

FIG. 9.39

Train routes of a passing train and a departure train in the same direction in train route combination II + III.

9.3 Precise calculation of headway in station

315

FIG. 9.40 Train routes of a passing train and a departure train in opposite directions in train route combination I + III.

FIG. 9.41 Train routes of a passing train and a departure train in opposite directions in train route combination II + III.

Figs. 9.40 and 9.41 respectively illustrate the route conflicts in the case of I + III and II + III. In Fig. 9.40, the preceding train passes through the station via Track IIG, and the following train departs via Track 5G. The train routes neither cross nor overlap, and thus there is no operation conflict. In Fig. 9.41, the preceding train passes through the station via Track IIG, and the following train departs via Track 4G in a “reverse departure” manner, resulting in possible operation conflict in the station throat on the side of the home signal S in the up direction. (15) An arrival train and a departure train in the same direction When adjacent trains successively arrive at and depart from a station in the same direction, they enter or leave the station through the different throats at the two ends. As a result, their routes neither cross nor overlap, and it is thus unnecessary to define the minimum headway between arrival time and departure time of such trains. (16) An arrival train and a departure train in opposite directions When adjacent trains successively arrive at and depart from a station in opposite directions, the train route combination might be I + I, II + II, or I +II, and the routes of the adjacent trains cross or overlap in the case of II + II and I + II. Assuming that adjacent trains run in down and up directions respectively, Figs. 9.42 and 9.44 respectively illustrate the route conflicts in the case of I + I, II + II, and I + II. In Fig. 9.42, the preceding train is received by Track 3G, and the following train departs via Track 4G.

316

9. Mechanism of enhancing the carrying capacity

FIG. 9.42 Train routes of an arrival train and a departure train in opposite directions in train route combination I + I.

The train routes neither cross nor overlap, and thus there is no operation conflict. In Fig. 9.43, the preceding train is received by Track 4G in a “reverse reception” manner, and the following train departs via Track 5G in a “reverse departure” manner, resulting in possible operation conflict in the station throat on the side of the home signal X in the down direction. In Fig. 9.44, the preceding train is received by Track 3G, and the following train departs via Track 5G in a “reverse departure” manner, resulting in possible operation conflict in the station throat on the side of the home signal X in the down direction. (17) A departure train and an arrival train in the same direction When adjacent trains successively depart from and arrive at a station in the same direction, they leave or enter the station through the different throats at the two ends. As a result, their routes neither cross nor overlap, and it is thus unnecessary to define the minimum headway between departure time and arrival time of such trains.

FIG. 9.43 Train routes of an arrival train and a departure train in opposite directions in train route combination II + II.

FIG. 9.44 Train routes of an arrival train and a departure train in opposite directions in train route combination I + II.

9.3 Precise calculation of headway in station

317

(18) A departure train and an arrival train in opposite directions When adjacent trains successively depart from and arrive at a station in opposite directions, the train route combination might be I + I, II + II, or I + II, and the routes of the adjacent trains cross or overlap in the case of II + II and I + II. Assuming that the two trains run in up and down directions respectively, Figs. 9.45 and 9.47 respectively illustrate the route conflicts in the case of I + I, II + II, and I + II. In Fig. 9.45, the preceding train departs via Track 4G, and the following train is received by Track 3G. The train routes neither cross nor overlap, and thus there is no operation conflict. In Fig. 9.46, the preceding train departs via Track 5G in a “reverse departure” manner, and the following train is received by Track 4G in a “reverse reception” manner, resulting in possible operation conflict in the station throat on the side of the home signal X in the down direction. In Fig. 9.47, the preceding train departs via Track 4G, and the following train is received by Track 6G in a “reverse reception” manner, resulting

FIG. 9.45 Train routes of a departure train and an arrival train in opposite directions in train route combination I + I.

FIG. 9.46 Train routes of a departure train and an arrival train in opposite directions in train route combination II + II.

FIG. 9.47 Train routes of a departure train and an arrival train in opposite directions in train route combination I + II.

318

9. Mechanism of enhancing the carrying capacity

in possible operation conflict in the station throat on the side of the reverse home signal XF in the down direction. 3. Set of headways in station According to the above analysis of the route conflicts between adjacent trains, 23 categories of station interval can be obtained, and the set of headways is shown as Table 9.2. TABLE 9.2 Set of typical headways for train pairs. Cat.

Operation state

Route combination

Operation direction

1

Arrival-arrival

I+I

Same direction

2

Arrival-arrival

II + II

Same direction

3

Arrival-arrival

I + II

Same direction

4

Departure-departure

I+I

Same direction

5

Departure-departure

II + II

Same direction

6

Departure-departure

I + II

Same direction

7

Passing-passing

III + III

Same direction

8

Arrival-passing

I + III

Same direction

9

Arrival-passing

II + III

Same direction

10

Arrival-passing

II + III

Opposite direction

11

Passing-arrival

I + III

Same direction

12

Passing-arrival

II + III

Same direction

13

Passing-arrival

II + III

Opposite direction

14

Departure-passing

I + III

Same direction

15

Departure-passing

II + III

Same direction

16

Departure-passing

II + III

Opposite direction

17

Passing-departure

I + III

Same direction

18

Passing-departure

II + III

Same direction

19

Passing-departure

II + III

Opposite direction

20

Arrival-departure

II + II

Opposite direction

21

Arrival-departure

I + II

Opposite direction

22

Departure-arrival

II + II

Opposite direction

23

Departure-arrival

I + II

Opposite direction

9.3 Precise calculation of headway in station

319

9.3.2.2 Characteristics of calculating headway in station based on time-space graph of train tracking operation According to the detailed introduction in Section 9.3.2.1, the method proposed in this chapter has the following characteristics compared with existing headway calculation methods: 1. Take the station and its adjacent sections as the study range, and give consideration to the operation process of the train in sections and at the station The operation state of arrival, departure, or passing of a train at a station affects the operation process in several block sections adjacent to the station. This is mainly reflected in that trains approaching the arrival and departure tracks from the diverging track need to decelerate to the diverging speed permitted before entering the station, trains departing the arrival and departure tracks to the diverging track need to accelerate to the section speed after leaving the station, and trains passing through the main track of the station need to decelerate to the allowable passing speed of the main track before entering the station if applicable. In addition, the neutral zone set in the block section adjacent to the station will further affect the headway in station. If the neutral zone is located in the inbound direction, the trains need to decelerate in advance to the diverging speed permitted on turnouts. If the neutral zone is located in the outbound direction, the trains cannot accelerate to the section speed in time after leaving the station, thus extending the time required for the first departure block section to clear. Therefore, in calculating the headway in station, it is necessary to take into account the operation process in sections and at stations, and take the station and its adjacent section as the study range. 2. Calculate headway in the station with specific train route combination In the station, train routes vary in track circuits and lengths, which affects the operation process of trains. On the other hand, the route combination of adjacent trains determines the route conflict area and affects the following operation process of adjacent trains. Consequently, the value of headway in station will change with the train route combination. 3. Follow station route setting and release rules based on the time-space graph of the train tracking operation The time-space graph of train tracking operation is developed with consideration to the high-speed railway operation rules, and the headway in station is calculated based on this diagram, which conforms to the existing station route setting and release rules.

320

9. Mechanism of enhancing the carrying capacity

(1) Route setting rules According to the station route setting rules, two or more trains are not allowed to operate simultaneously in the same route protected by the signal, and before a route is established, all track circuits on it must be vacant, all turnouts covered by it must be correctly positioned, and no conflicting route is established. (2) Route release rules Track circuits of a section are automatically released whenever the section clears. In the segmentation release mode, the time of handling the following train route shall be analyzed considering the route conflict area. Many crossovers and turnouts are set in the throat of large station. The route of the following train can only be handled after the preceding arrival train entirely runs past the district by which the following train route crosses or overlaps. As shown in Fig. 9.48, the following train does not need to wait until the tail of the preceding train runs past the insulation joint at the reverse departure signal S5, and instead, a passing route can be set for the following train once the tail of the preceding train runs past the insulation joint between No. 13 and No. 15 turnouts.

9.3.3 Calculation model of headway in station Based on the above, in this part, a calculation model of the headway in station is established to calculate headways in station [2]. 9.3.3.1 Definitions of symbols 1. The set symbols involved in the model and their meanings are shown in Table 9.3 2. The parameter symbols involved in the model and their meanings are shown in Table 9.4 3. The variable symbols involved in the model and their meanings are shown in Table 9.5

FIG. 9.48

Train routes of an arrival train and a passing train in the same direction.

321

9.3 Precise calculation of headway in station

TABLE 9.3 Sets. Symbol

Definition

Q

Set of the train occupation units the train passes, which is determined according to the train operation direction, q  Q

Qsec

Set of section track circuits the train passes, which is determined according to the train operation direction, qsec  Qsec

Qsta

Set of the minimum block sections in the station along the train route, which is determined according to the train operation direction, qsta  Qsta

Q sta +

Set of the second and subsequent minimum block sections in the station along the train route, which is determined according to the train operation direction

R

Set of the block sections through which the train passes, which is determined according to the train operation direction, r  R

Qr

Set of the track circuits in the block section r  R determined according to the train operation direction, where the track circuit in the block section r  R is denoted as qr  Qr

Q r+

Set of the second and subsequent track circuits in the block section r  R, which is determined according to on the train operation direction

QCsta

Route operation conflict area in the station

TABLE 9.4 Parameters. Symbol

Definition

i

Train, where i  {1, 2}. If i ¼ 1, the train i is the preceding train; otherwise, the train i is the following train

q

Section track circuit and minimum block section in the station, where q  Q

qsec

Section track circuit, where qsec  Qsec

qsta

Minimum block section in the station, where qsta  Qsta

r

Block section, where r  R

q0

First train occupation unit in the train operation direction, where q0  Q

qsec 0

The first section track circuit through which the train passes in the train sec operation direction, where qsec 0 Q

qr0

The first track circuit in the block section r  R in the train operation direction, where qr0  Qr and {qr0} [ Q r+ ¼ Qr

qwc,

d

Minimum block section in the station where the switchless section on the arrival and departure track is located

qwc,

z

Minimum block section in the station where the switchless section on the middle of the main track of the station is located Continued

322

9. Mechanism of enhancing the carrying capacity

TABLE 9.4 Parameters—cont’d Symbol

Definition

zt

The operation status of adjacent trains, zt  {dd, ff, tt, dt, td, ft, tf, df, fd}, where dd denotes arrival-arrival; ff denotes departure-departure; tt denotes passingpassing; dt denotes arrival-passing; td denotes passing-arrival; ft denotes departure-passing; tf denotes passing-departure; df denotes arrival-departure; fd denotes departure-arrival

j

Type of the route of the preceding train, where j  {I, II, III}

k

Type of the route of the following train, where k  {I, II, III}

fx

Operation direction of adjacent trains, fx  {tx, dx}, where tx denotes they are in the same direction; dx denotes they are in the opposite directions

tiaq, q

Running time of the train i within the safety protection distance in the train occupation unit q

tirou,

q

Preparation time of the train i in the train occupation unit q

tirea, q

Reaction time of the train i in the train occupation unit q

tiapp, q

Braking time of the train i in the train occupation unit q

ticon, q

Continuous time of the train i in the train occupation unit q

tiocc, q

Running time of the train i in the train occupation unit q

ticle,

Clearing time of the train i in the train occupation unit q

q

tirel, q

Closing time of the train i in the train occupation unit q

TABLE 9.5 Variables. Symbol

Definition

Ij,zt,k fx

Headway in station when operation status is zt, operation direction is fx and route are j and k of adjacent trains

biq

The time when the train i begins to occupy the train occupation unit q, i.e., the starting time of the preparation time

eiq

The time when the train i ends occupying the train occupation unit q, i.e., the ending time of the closing time

birea,

q

Starting time of reaction time of the train i in the train occupation unit q

biapp, q

Starting time of braking time of the train i in the train occupation unit q

bicon, q

Starting time of continuous time of the train i in the train occupation unit q

biocc,

q

Starting time of running time of the train i in the train occupation unit q

bicle, q

Starting time of clearing time of the train i in the train occupation unit q

birel, q

Starting time of closing time of the train i in the train occupation unit q

9.3 Precise calculation of headway in station

323

9.3.3.2 Objective function The objective function of the calculation model is to minimize the headway [1], as follows: j,k

min I zt,fx

(9.6)

ztfdd, ff , tt, dt, td, ft, tf , df , fdg,jfI, II, IIIg,kfI, II, IIIg,fxftx, dxg The train arrival time is the time when the train comes to a complete stop on the arrival and departure tracks. In the minimum block section in station qwc, d where the switchless section on the arrival and departure track is located, the time when the train i comes to a complete stop is the ending time of the running time in the train occupation time in qwc, d, i.e., i the starting time bcle,q wc,d of the clearing time. The train departure time is the time when the train starts and accelerates on the arrival and departure tracks. In the minimum block section in station qwc, d where the switchless section on the arrival and departure track is located, the time when the train i starts and accelerates is the starti wc, d ing time bocc,q wc,d of the running time in the train occupation time in q . The passing time of the train is the time when the train enters the block section in the station where the main track IG or IIG is located. In the minimum block section qwc, z where the switchless section in the middle of the main track of the station is located, the passing time of the train i is the i wc, z starting time bocc,q wc,z of the running time in q . j, k On this basis, the specific headway Izt, fx of adjacent trains in the case of different operation status, route types and operation direction combinations are shown in Eq. (9.7). 8 > b2cle,qwc,d  b1cle,qwc,d zt ¼ dd, jfI, IIg, kfI, IIg, fx ¼ tx > > > > > > b2occ,qwc,d  b1occ,qwc,d zt ¼ ff , jfI, IIg, kfI, IIg, fx ¼ tx > > > > > > 2 > b wc,z  b1occ,qwc,z zt ¼ tt, j ¼ III, k ¼ III, fx ¼ tx > > > occ,q > > > > > b2occ,qwc,z  b1cle,qwc,d zt ¼ dt, jfI, IIg, k ¼ III, fxftx, dxg > > < j,k I zt,fx ¼ b2cle,qwc,d  b1occ,qwc,z zt ¼ td, j ¼ III, kfI, IIg, fxftx, dxg (9.7) > > > > > b2occ,qwc,z  b1occ,qwc,d zt ¼ ft, jfI, IIg, k ¼ III, fxftx, dxg > > > > > > > b2occ,qwc,d  b1occ,qwc,z zt ¼ tf , j ¼ III, kfI, IIg, fxftx, dxg > > > > > > > > b2occ,qwc,d  b1cle,qwc,d zt ¼ df , jfI, IIg, kfI, IIg, fx ¼ dx > > > > 2 : bcle,qwc,d  b1occ,qwc,d zt ¼ fd, jfI, IIg, kfI, IIg, fx ¼ dx

324

9. Mechanism of enhancing the carrying capacity

9.3.3.3 Constraints 1. Initialization constraints The calculation model of the headway in station takes the station and its adjacent section as the study range. Thus, the time when the preceding sec train i ¼ 1 starts to occupy the first section track circuit qsec in the train 0 Q operation direction within the section is set to 0, as shown in Eq. (9.8). b1q sec ¼ 0 0

(9.8)

2. Continuity constraints of train occupation time (1) The first train occupation unit in the block section or train route For the first train occupation unit in the block section or train route in the train operation direction, the occupation time includes preparation time, reaction time, braking time, running time, clearing time, and closing time. qr0  Qr represents the first track circuit in the block section r  R in the sta train operation direction, and qsta represents the first minimum 0 Q block section in the station along the train route in the train operation direction. Due to the Continuity of the train occupation time, the starting time of the reaction time is equal to the sum of the ending time of the preparation time, as shown in Eqs. (9.9) and (9.15); the starting time of the braking time is equal to the ending time of the reaction time, as shown in Eqs. (9.10) and (9.16); the starting time of the running time is equal to the ending time of the braking time, as shown in Eqs. (9.11) and (9.17); the starting time of the clearing time is equal to the ending time of the running time, as shown in Eqs. (9.12) and (9.18); the starting time of the closing time is equal to the ending time of the clearing time, as shown in Eqs. (9.13) and (9.19); the ending time of the train occupation time is the ending time of the closing time, as shown in Eqs. (9.14) and (9.20). Section: birea,qr ¼ biqr + tirou,qr ,8if1, 2g,8rR

(9.9)

biapp,qr ¼ birea,qr + tirea,qr ,8if1, 2g,8rR

(9.10)

biocc,qr ¼ biapp,qr + tiapp,qr ,8if1, 2g,8rR

(9.11)

birel,qr ¼ bicle,qr + ticle,qr ,8if1, 2g,8rR

(9.12)

bicle,qr ¼ biocc,qr + tiocc,qr ,8if1, 2g,8rR

(9.13)

eiqr ¼ birel,qr + tirel,qr ,8if1, 2g,8rR

(9.14)

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

9.3 Precise calculation of headway in station

325

birea,qsta ¼ biqsta + tirou,qsta ,8if1, 2g

(9.15)

biapp,qsta ¼ birea,qsta + tirea,qsta ,8if1, 2g

(9.16)

biocc,qsta ¼ biapp,qsta + tiapp,qsta ,8if1, 2g

(9.17)

bicle,qsta ¼ biocc,qsta + tiocc,qsta ,8if1, 2g

(9.18)

birel,qsta ¼ bicle,qsta + ticle,qsta ,8if1, 2g

(9.19)

eiqsta ¼ birel,qsta + tirel,qsta ,8if1, 2g

(9.20)

Station: 0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

(2) The second and subsequent train occupation units in the block section or train route For the second and subsequent train occupation units in the train operation direction, the occupation time includes preparation time, reaction time, continuous time, running time, clearing time, and closing time. Among them, the preparation time, reaction time, running time, clearing time, and closing time of each train occupation unit can be calculated in advance, and they are the input data of the model. It is worth noting that the continuous time depends on the ending time of the reaction time and the starting time of the running time. Due to the Continuity of the train occupation time, the starting time of the reaction time is equal to the ending time of the preparation time, as shown in Eqs. (9.21) and (9.26); the starting time of the continuous time is equal to the ending time of the reaction time, as shown in Eqs. (9.22) and (9.27); the starting time of the clearing time is equal to the ending time of the running time, as shown in Eqs. (9.23) and (9.28); the starting time of the closing time is equal to the ending time of the clearing time, as shown in Eqs. (9.24) and (9.29); the ending time of the train occupation time is equal to the ending time of the closing time, as shown in Eqs. (9.25) and (9.30). Section: birea,qr ¼ biqr + tirou,qr ,8if1, 2g,8qr Qr+ ,8rR

(9.21)

bicon,qr ¼ birea,qr + tirea,qr ,8if1, 2g,8qr Qr+ ,8rR

(9.22)

bicle,qr ¼ bioccqr + tiocc,qr ,8if1, 2g,8qr Qr+ ,8rR

(9.23)

birel,qr ¼ bicle,qr + ticle,qr ,8if1, 2g,8qr Qr+ ,8rR

(9.24)

eiqr ¼ birel,qr + tirel,qr ,8if1, 2g,8qr Qr+ ,8rR

(9.25)

326

9. Mechanism of enhancing the carrying capacity

Station: birea,qsta ¼ biqsta + tirou,qsta ,8if1, 2g,8qsta Qsta +

(9.26)

bicon,qsta ¼ birea,qsta + tirea,qsta ,8if1, 2g,8qsta Qsta +

(9.27)

bicle,qsta ¼ biocc,qsta + tiocc,qsta ,8if1, 2g,8qsta Qsta +

(9.28)

birel,qsta ¼ bicle,qsta + ticle,qsta ,8if1, 2g,8qsta Qsta +

(9.29)

eiqsta ¼ birel,qsta + tirel,qsta ,8if1, 2g,8qsta Qsta +

(9.30)

3. Correlation constraints on the occupation time of different train occupation units For each block section or train route, all the train occupation units start to be occupied by the train at the same time, so the starting time of the occupation time of the second and subsequent train occupation units is equal to the starting time of the occupation time of the first train occupation unit, as shown in Eqs. (9.31) and (9.32). Section: biqr ¼ biqr ,8if1, 2g,8qr Qr+ ,8rR

(9.31)

biqsta ¼ biqsta ,8if1, 2g,8qsta Qsta +

(9.32)

0

Station: 0

4. Continuity constraint during train operation The train operates continuously in station and sections, occupying the train occupation units in sequence. The starting time of the clearing time in the train occupation unit q is equal to the time when the head of the train enters the next train occupation unit q + 1, which can be expressed as the starting time of the running time plus the running time within the safety protection distance. Therefore, the continuity constraint of the train operation process are uniformly expressed in Eq. (9.33). bicle,q ¼ biocc,q+1 + tiaq,q+1 ,8if1, 2g,8qQ,8q + 1Q

(9.33)

5. Elimination constraints of train operation conflicts To eliminate the operation conflicts between adjacent trains, they both are not allowed to occupy the same train operation conflict area at the same time, and the following train can start to occupy this area only after

9.3 Precise calculation of headway in station

327

the preceding train ceases occupying it. Therefore, for any train occupation unit in the train operation conflict area, the ending time of the occupation time of the preceding train cannot be earlier than the starting time of the occupation time of the following train, which is expressed in Eqs. (9.34) and (9.35). Section: b2qr  e1qr  0,8qr Qr ,8rR

(9.34)

b2qsta  e1qsta  0,8qsta QCsta

(9.35)

Station:

The bottleneck is a position that limits the further shortening of the headway in station. In the section, if 9qr  Qr, 9 r  R, there will be bq2r ¼ eq1r, then qr is the bottleneck. In the station, if 9 qsta  QCsta, there will be bq2sta ¼ eq1sta, then qsta is the bottleneck. 6. Integer constraints All variables are nonnegative integers as shown in Eqs. (9.36) and (9.37), because the preparation time, reaction time, braking time, running time, and clearing time are accurate to 1 s. biq sec ,eiq sec ,birea,q sec ,biapp,q sec ,bicon,q sec ,biocc,q sec ,bicle,q sec ,birel,q sec Ζ+ ,8if1, 2g; 8q sec Q sec (9.36) biqsta ,eiqsta ,birea,qsta ,biapp,qsta ,bicon,qsta ,biocc,qsta ,bicle,qsta ,birel,qsta Ζ+ ,8if1, 2g; 8qsta Qsta (9.37)

9.3.4 Analysis of calculation results Based on the model established in the above, this part is to design the algorithm to calculate the different headways in station, and to position the bottlenecks. Finally, a case is introduced for analysis. 9.3.4.1 Model solution algorithm The steps of the solution algorithm for the constructed model are as follows: Step 1: Select two train routes from the station route set as the route combination of adjacent trains, and record the total route length; Step 2: Take the station and its adjacent section as the study range, and depict the time-space graphs of train tracking operation in the station and section; Step 3: Calculate the train occupation time, and then calculate headways in station;

328

9. Mechanism of enhancing the carrying capacity

Step 3.1: Calculate the occupation time of the preceding train and the following train; (1) According to the train operation direction, initialize the time when the preceding train and the following train begin to occupy the first track circuit in the section to 0. (2) Calculate the occupation time of the preceding train and the following train in each train occupation unit according to the constraint Eqs. (9.9)–(9.33). (3) Eliminate the operation conflicts between adjacent trains and identify the bottlenecks according to the objective function and constraint Eqs. (9.34) and (9.35). The occupation time of the following train needs to be postponed as a whole to avoid the operation conflicts. Calculate bq2r  eq1r for each track circuit in the section, and calculate bq2sta  eq1sta for the minimum block sections in the station, and then take the greatest one as the overall delay time of the occupation time of the following train, and mark the corresponding train occupation unit as the bottleneck. (4) Update the occupation time of the following train. The occupation time of the following train in each train occupation unit is delayed by Tyh, to eliminate the operation conflicts. Step 3.2: Determine the type of headway in station according to the operation state, route combination, and operation direction of adjacent trains; Step 3.3: Calculate the headway in station according to Eq. (9.7). Step 4: Confirm whether all route combinations in the station route set have been traversed; if yes, calculate the maximum, minimum, and average values of different types of headway in the station, and end; otherwise, select a route combination not traversed, and return to Step 1. 9.3.4.2 Case study 1. Introduction to case The district from Xuzhou East to Bengbu South is taken as the object of the case study. The study range covers four sections, namely DingyuanBengbu South, Bengbu South-Suzhou East, Suzhou East-Xuzhou East, Xuzhou East-Zaozhuang West, and three stations, namely Bengbu South Station, Suzhou East Station, and Xuzhou East Station. The headway in each station is calculated by using the above-mentioned model and the designed solution algorithm. 2. Basic data Basic data includes three categories, namely line data, EMU data, and station data.

329

9.3 Precise calculation of headway in station

(1) Line data Line data includes the beginning and ending chainages, grade section, neutral zone, speed limit area, etc. of the section. The data of some lines in the up direction are shown in Tables 9.6–9.9. Since there is few data, and the additional resistance due to curve and that due to tunnel are small, only the additional resistance due to grade is considered in the calculation. TABLE 9.6 Beginning and ending chainages of sections in up direction. Section

Beginning chainage (m)

Ending chainage (m)

Number of block sections

Dingyuan-Bengbu South

902,172

850,381

28

Bengbu South-Suzhou East

847,295

761,707

46

Suzhou East-Xuzhou East

759,878

694,964

35 (36 for down direction)

Xuzhou East-Zaozhuang West

691,895

629,285

34

TABLE 9.7 Slope sections in up direction. S/N

Gradient (%)

Length (m)

Beginning chainage (m)

1

0

93

902,172

2

7

907

902,079

3

3

1200

901,172

4

4

3000

899,972

5

13

1000

896,972

6

1

1909

895,972

7

9

1801

894,063

8

2

1490

892,262

9

10

1410

890,772

10

6

907

889,362

…

…

…

…

TABLE 9.8 Phase separation areas in up direction. S/N

Beginning chainage (m)

Ending chainage (m)

Length (m)

1

880,700

880,204

496

2

852,146

851,650

496

3

827,481

826,985

496

…

…

…

…

330

9. Mechanism of enhancing the carrying capacity

TABLE 9.9 Speed limitation in up direction. S/N

Speed (km/h)

Length (m)

Beginning chainage (m)

1

380

47,319

902,172

2

380

272

854,853

3

320

230

854,581

...

…

…

…

(2) EMU data CRH380B, with a converted length of 18.5 m, a train length of 203.5 m, a total weight of 542.2 t, and a maximum operating speed of 380 km/h, is used in this study. Its traction and braking characteristic curves are shown in Fig. 9.49. (3) Station data a. Station topology The station topological structures of Xuzhou East Station, Suzhou East Station, and Bengbu South Station are shown in Figs. 9.50–9.52. b. Station route information Train receiving, departure, and through route are closely related to the calculation of headway in the station. Take Xuzhou East Station as an example, and the basic routes are as shown in Table 9.10. 3. Temporal-spatial graph of train tracking operation (1) Division results of train occupation units Taking Xuzhou East Station as an example, this part only shows the division results of the minimum block section in the station, as presented in Table 9.11. In column 2, “{ }” indicates a minimum block section in the station. Columns 3 and 4 show the linkage turnout and the intrusion insulation joint to be considered in the division process. Column 3 shows the two groups of turnouts in the linkage turnout, while column 4 shows the two groups of turnouts adjacent to the intrusion insulation joint. Column 5 shows the number of minimum block sections in the station, through which the route passes. (2) Quantification of train occupation time a. Quantification of arrival train occupation time Take the arrival train received via 6G at Xuzhou East Station in up direction as an example. Fig. 9.53 shows the train occupation units and occupation time in Suzhou East-Xuzhou East section and

FIG. 9.49 Traction and braking curve of CRH380B EMU.

332

9. Mechanism of enhancing the carrying capacity

FIG. 9.50

Layout of Xuzhou East station.

FIG. 9.51

Layout of Suzhou East station.

FIG. 9.52

Layout of Bengbu South station.

Xuzhou East Station. In this figure, the horizontal axis represents the space axis, the vertical axis represents the time, the curve represents the actual moving path of the train, and the rectangular box represents the occupation time in each train occupation unit. On this basis, the proportion of preparation time, reaction time, braking time (or continuous time), operating time, clearing time, and closing time in the occupation time is shown in Fig. 9.54, and the corresponding stacked chart is shown in Fig. 9.55. The two longitudinal dotted lines represent the position where the train begins to accelerate to the speed over section after departing from the station and the position where the train begins to decelerate before entering the station. The blue area represents the station. b. Quantification of departure train occupation time Take the departure train from Xuzhou East Station via 6G in up direction as an example. Fig. 9.56 shows the train occupation units

TABLE 9.10

Basic train routes and corresponding turnouts in Xuzhou East station.

Track Turnouts

Route length (m)

IG

4,6,12,14,22

2006

IIG

4,6,12,26

2006

39

IIIG

4,6,12,14,22,24,38

1801

1268

40

IVG

4,6,12,26,28,42

1801

1268

41

IVG

4,6,8,10,30,28,42

1801

5G

33,31,19,17,15,13,5,3,51 1327

42

5G

4,6,12,14,22,24,38,40

1742

7

6G

41,39,23,21,13,5,3,51

1327

43

6G

4,6,12,26,28,42,44

1742

8

6G

41,39,23,35,7,5,3,51

1327

44

6G

4,6,8,10,30,28,42,44

1742

9

7G

33,31,19,17,15,13,5,3,51 1327

45

7G

4,6,12,14,22,24,38,40

1742

10

8G

41,39,23,21,13,5,3,51

1327

46

8G

4,6,12,26,28,42,44

1742

11

8G

41,39,23,35,7,5,3,51

1327

47

8G

4,6,8,10,30,28,42,44

1742

12

10G

43,37,35,7,5,3,51

1325

48

10G

4,6,8,10,30,32,46

1744

13

12G

43,37,35,7,5,3,51

1325

49

12G

4,6,8,10,30,32,46

1744

14

14G

45,37,35,7,5,3,51

1325

50

14G

4,6,8,10,30,32,48

1744

15

16G

45,37,35,7,5,3,51

1325

51

16G

4,6,8,10,30,32,48

1744

Track Turnouts

Route length (m)

Route No.

IG

15,17,13,5,3,51

1063

37

IIG

21,13,5,3,51

1063

38

3

IIIG

31,19,15,17,13,5,3,51

1268

4

IVG

39,23,21,13,5,3,51

5

IVG

39,23,35,7,5,3,51

6

Route No. 1 2

Route type Train departure

Up

Route type Train receiving

Up

Continued

TABLE 9.10

Basic train routes and corresponding turnouts in Xuzhou East station—cont’d

Track Turnouts

Route length (m)

IG

47,1,9,15,17

2140

53

IIG

47,1,3,5,13,21

2140

1072

54

IIIG

47,1,9,15,17,19,31

1997

38,24,20,18,16,2

1072

55

IIIG

47,1,9,11,25,19,31

1997

IVG

42,28,26,12,6,4,2

1072

56

IVG

47,1,3,5,13,21,23,39

1997

21

IVG

42,28,30,10,8,6,4,2

1072

57

IVG

47,1,3,5,7,35,23,39

1997

22

5G

40,38,24,22,14,16,2

1123

58

5G

47,1,9,15,17,19,31,33

1946

23

5G

40,38,24,20,18,16,2

1123

59

5G

47,1,9,11,25,19,31,33

1946

24

6G

44,42,28,26,12,6,4,2

1123

60

6G

47,1,3,5,13,21,23,39,41 1946

25

6G

44,42,28,30,10,8,6,4,2

1123

61

6G

47,1,3,5,7,35,23,39,41

1946

26

7G

40,38,24,22,14,16,2

1123

62

7G

47,1,9,15,17,19,31,33

1946

27

7G

40,38,24,20,18,16,2

1123

63

7G

47,1,9,11,25,19,31,33

1946

28

8G

44,42,28,26,12,6,4,2

1123

64

8G

47,1,3,5,13,21,23,39,41 1946

29

8G

44,42,28,30,10,8,6,4,2

1123

65

8G

47,1,3,5,7,35,23,39,41

1946

30

9G

36,34,20,18,16,2

1125

66

9G

47,1,9,11,25,27,29

1944

31

10G

46,32,30,10,8,6,4,2

1131

67

10G

47,1,3,5,7,35,37,43

1938

32

11G

36,34,20,18,16,2

1125

68

11G

47,1,9,11,25,27,29

1944

Track Turnouts

Route length (m)

Route No.

IG

22,14,16,2

929

52

17

IIG

26,12,6,4,2

929

18

IIIG

38,24,22,14,16,2

19

IIIG

20

Route No. 16

Route type Down

Route type Down

33

12G

46,32,30,10,8,6,4,2

1131

69

12G

47,1,3,5,7,35,37,43

1938

34

13G

34,20,18,16,2

1074

70

13G

47,1,9,11,25,27

1995

35

14G

48,32,30,10,8,6,4,2

1128

71

14G

47,1,3,5,7,35,37,45

1941

36

16G

48,32,30,10,8,6,4,2

1128

72

16G

47,1,3,5,7,35,37,45

1941

Up

IIG

4,6,12,26,21,13,5,3,51

3069

Down

IG

47,1,9,15,17,14,16,2

3069

73 74

Passing

TABLE 9.11 Train routes and corresponding track sections in Xuzhou East station. Factors to be considered Route No.

Minimum block sections at the station on the route

Linkage turnout

Intrusion insulation joint

Number of minimum block sections in station

1

{15-17DG,5-13DG},3-51DG

13,15

2

21DG,5-13DG,3-51DG

3

{19-31DG,15-17DG},{15-17DG,5-13DG},3-51DG

17,19;13,15

3

4

{23-39DG,21DG},5-13DG,3-51DG

21,23

3

5

{23-39DG,35DG},{7DG,5-13DG},3-51DG

5,7

23,35

3

6

{33DG,19-31DG},{19-31DG,15-17DG},{15-17DG,513DG},3-51DG

17,19;13,15

31,33

4

7

{41DG,23-39DG},{23-39DG,21DG},5-13DG,3-51DG

21,23

39,41

4

8

{41DG,23-39DG},{23-39DG,35DG},{7DG,5-13DG},351DG

5,7

39,41;23,35

4

9

{33DG,19-31DG},{19-31DG,15-17DG},{15-17DG,513DG},3-51DG

17,19;13,15

31,33

4

10

{41DG,23-39DG},{23-39DG,21DG},5-13DG,3-51DG

21,23

39,41

4

11

{41DG,23-39DG},{23-39DG,35DG},{7DG,5-13DG},351DG

5,7

39,41;23,35

4

12

43DG,{37DG,35DG},{7DG,5-13DG},3-51DG

5,7

35,37

4

13

43DG,{37DG,35DG},{7DG,5-13DG},3-51DG

5,7

35,37

4

2 3

14

45DG,{37DG,35DG},{7DG,5-13DG},3-51DG

5,7

35,37

4

15

45DG,{37DG,35DG},{7DG,5-13DG},3-51DG

5,7

35,37

4

16

{14-22DG,16DG},2DG

14,16

2

17

26DG,6-12DG,{4DG,2DG}

2,4

18

{24-38DG,14-22DG},{14-22DG,16DG},2DG

22,24

14,16

3

19

{24-38DG,18-20DG},{18-20DG,16DG},2DG

16,18

20,24

3

20

{28-42DG,26DG},6-12DG,{4DG,2DG}

26,28;2,4

21

{28-42DG,30-32DG},{8-10DG,6-12DG},{4DG,2DG}

6,8;2,4

28,30

3

22

{40DG,24-38DG},{24-38DG,14-22DG},{1422DG,16DG},2DG

22,24

38,40;14,16

4

23

{40DG,24-38DG},{24-38DG,18-20DG},{1820DG,16DG},2DG

16,18

38,40;20,24

4

24

{44DG,28-42DG},{28-42DG,26DG},6-12DG, {4DG,2DG}

26,28;2,4

42,44

4

25

{44DG,28-42DG},{28-42DG,30-32DG},{8-10DG,612DG},{4DG,2DG}

6,8;2,4

42,44;28,30

4

26

{40DG,24-38DG},{24-38DG,14-22DG},{1422DG,16DG},2DG

22,24

38,40;14,16

4

27

{40DG,24-38DG},{24-38DG,18-20DG},{1820DG,16DG},2DG

16,18

38,40;20,24

4

28

{44DG,28-42DG},{28-42DG,26DG},6-12DG, {4DG,2DG}

26,28;2,4

42,44

4

3

3

Continued

TABLE 9.11 Train routes and corresponding track sections in Xuzhou East station—cont’d Factors to be considered Route No.

Minimum block sections at the station on the route

Linkage turnout

Intrusion insulation joint

Number of minimum block sections in station

29

{44DG,28-42DG},{28-42DG,30-32DG},{8-10DG,612DG},{4DG,2DG}

6,8;2,4

42,44;28,30

4

30

{36DG,34DG},{18-20DG,16DG},2DG

16,18

34,36

3

31

46DG,30-32DG,{8-10DG,6-12DG},{4DG,2DG}

6,8;2,4

32

{36DG,34DG},{18-20DG,16DG},2DG

16,18

33

46DG,30-32DG,{8-10DG,6-12DG},{4DG,2DG}

Linkage turnouts 10;2,4

4

34

34DG,{18-20DG,16DG},2DG

16,18

3

35

48DG,30-32DG,{8-10DG,6-12DG},{4DG,2DG}

6,8;2,4

4

36

48DG,30-32DG,{8-10DG,6-12DG},{4DG,2DG}

6,8;2,4

4

37

4DG,{6-12DG,14-22DG},IG2,IG1

12,14

4

38

4DG,6-12DG,26DG,IIG2,IIG1

39

4DG,{6-12DG,14-22DG},{14-22DG,24-38DG},IIIG2, IIIG1

12,14;22,24

5

40

4DG,6-12DG,{26DG,28-42DG},IVG2,IVG1

26,28

5

41

4DG,{6-12DG,8-10DG},{30-32DG,28-42DG},IVG2, IVG1

6,8

4 34,36

3

5

28,30

5

42

4DG,{6-12DG,14-22DG},{14-22DG,24-38DG},{2438DG,40DG},5G

12,14;22,24

38,40

5

43

4DG,6-12DG,{26DG,28-42DG},{28-42DG,44DG},6G

26,28

42,44

5

44

4DG,{6-12DG,8-10DG},{30-32DG,28-42DG},{2842DG,44DG},6G

6,8

28,30;42,44

5

45

4DG,{6-12DG,14-22DG},{14-22DG,24-38DG},{2438DG,40DG},7G

12,14;22,24

38,40

5

46

4DG,6-12DG,{26DG,28-42DG},{28-42DG,44DG},8G

26,28

42,44

5

47

4DG,{6-12DG,8-10DG},{30-32DG,28-42DG},{2842DG,44DG},8G

6,8

28,30;42,44

5

48

4DG,{6-12DG,8-10DG},30-32DG,46DG,10G

6,8

5

49

4DG,{6-12DG,8-10DG},30-32DG,46DG,12G

6,8

5

50

4DG,{6-12DG,8-10DG},30-32DG,48DG,14G

6,8

5

51

4DG,{6-12DG,8-10DG},30-32DG,48DG,16G

6,8

5

52

47DG,{1-9DG,15-17DG},IG1,IG2

53

47DG,{1-9DG,3-51DG},5-13DG,21DG,IIG1,IIG2

1,3

54

47DG,{1-9DG,15-17DG},{15-17DG,19-31DG},IIIG1, IIIG2

17,19

9,15

5

55

47DG,{1-9DG,11DG},{25DG,19-31DG},IIIG1,IIIG2

9,11

19,25

5

56

47DG,{1-9DG,3-51DG},5-13DG,{21DG,23-39DG}, IVG1,IVG2

1,3;21,23

9,15

4 6

6 Continued

TABLE 9.11 Train routes and corresponding track sections in Xuzhou East station—cont’d Factors to be considered Route No.

Minimum block sections at the station on the route

Linkage turnout

Intrusion insulation joint

Number of minimum block sections in station

57

47DG,{1-9DG,3-51DG},{5-13DG,7DG},{35DG,2339DG},IVG1,IVG2

1,3;5,7

23,35

6

58

47DG,{1-9DG,15-17DG},{15-17DG,19-31DG},{1931DG,33DG},5G

17,19

9,15;31,33

5

59

47DG,{1-9DG,11DG},{25DG,19-31DG},{1931DG,33DG},5G

9,11

19,25;31,33

5

60

47DG,{1-9DG,3-51DG},5-13DG,{21DG,23-39DG},{2339DG,41DG},6G

1,3;21,23

39,41

6

61

47DG,{1-9DG,3-51DG},{5-13DG,7DG},{35DG,2339DG},{23-39DG,41DG},6G

1,3;5,7

23,35;39,41

6

62

47DG,{1-9DG,15-17DG},{15-17DG,19-31DG},{1931DG,33DG},7G

17,19

9,15;31,33

5

63

47DG,{1-9DG,11DG},{25DG,19-31DG},{1931DG,33DG},7G

9,11

19,25;31,33

5

64

47DG,{1-9DG,3-51DG},5-13DG,{21DG,23-39DG},{2339DG,41DG},8G

1,3;21,23

39,41

6

65

47DG,{1-9DG,3-51DG},{5-13DG,7DG},{35DG,2339DG},{23-39DG,41DG},8G

1,3;5,7

23,35;39,41

6

66

47DG,{1-9DG,11DG},25DG,{27DG,29DG},9G

9,11

27,29

5

67

47DG,{1-9DG,3-51DG},{5-13DG,7DG}, {35DG,37DG},43DG,10G

1,3;5,7

35,37

6

68

47DG,{1-9DG,11DG},25DG,{27DG,29DG},11G

9,11

27,29

5

69

47DG,{1-9DG,3-51DG},{5-13DG,7DG}, {35DG,37DG},43DG,12G

1,3;5,7

35,37

6

70

47DG,{1-9DG,11DG},25DG,27DG,13G1,13G2

9,11

71

47DG,{1-9DG,3-51DG},{5-13DG,7DG}, {35DG,37DG},45DG,14G

1,3;5,7

35,37

6

72

47DG,{1-9DG,3-51DG},{5-13DG,7DG}, {35DG,37DG},45DG,16G

1,3;5,7

35,37

6

73

4DG,6-12DG,26DG,IIG2,IIG1,21DG,5-13DG,3-51DG

74

47DG,{1-9DG,15-17DG},IG1,IG2,{1422DG,16DG},2DG

6

8 9,15;14,16

6

342

9. Mechanism of enhancing the carrying capacity

FIG. 9.53

Occupation units and corresponding occupation time for an arrival train.

FIG. 9.54

Construction of occupation time in each occupation unit for an arrival train.

FIG. 9.55

Stacked chart of occupation time in each occupation unit for an arrival train.

9.3 Precise calculation of headway in station

FIG. 9.56

343

Occupation units and corresponding occupation time for a departure train.

and occupation time in Xuzhou East Station and Xuzhou EastZaozhuang West section. Similarly, the horizontal axis represents the space, the vertical axis represents the time, the curve represents the actual moving path of the train, and the rectangular box represents the train occupation time in each train occupation unit. On this basis, the proportion of preparation time, reaction time, braking time (or continuous time), operating time, clearing time, and closing time in the occupation time is shown in Fig. 9.57, and the corresponding stacked chart is shown in Fig. 9.58. The two longitudinal dotted lines represent the position where the train begins to accelerate to the speed over section after departing from the station and the position where the train begins to decelerate before it entering the station. The blue area represents the station. c. Quantification of passing train occupation time Take the passing train through Xuzhou East Station via the main track IIG in up direction as an example. Fig. 9.59 shows the train occupation units and occupation time in Suzhou East-Xuzhou East

FIG. 9.57

Construction of occupation time in each occupation unit for a departure train.

344

9. Mechanism of enhancing the carrying capacity

FIG. 9.58 Stacked chart of occupation time in each occupation unit for a departure train.

FIG. 9.59

Occupation units and corresponding occupation time for a passing train.

section, Xuzhou East Station, and Xuzhou East-Zaozhuang West section. Similarly, the horizontal axis represents the space, the vertical axis represents the time, the curve represents the actual moving path of the train, and the rectangular box represents the train occupation time in each train occupation unit. On this basis, the proportion of preparation time, reaction time, braking time (or continuous time), operating time, clearing time, and closing time in the occupation time is shown in Fig. 9.60, and the corresponding stacked chart is shown in Fig. 9.61. The blue area represents the station. 4. Calculation results of headway in Xuzhou East Station There are 74 basic routes at Xuzhou East Station, as shown in Table 9.10. Considering the four combinations of operating speeds (i.e., 300–300, 350–350, 300–350, 350–300 km/h) of adjacent trains, there are 74  73  4 ¼ 21,608 route combinations for adjacent trains. It is necessary to check one by one whether there are operation conflicts between adjacent

9.3 Precise calculation of headway in station

345

FIG. 9.60

Construction of occupation time in each occupation unit for a passing train.

FIG. 9.61

Stacked chart of occupation time in each occupation unit for a passing train.

trains under different train route combinations, and further calculate the minimum headway. According to Table 9.1, there are 23 types of headway. Considering that there may be multiple train route combinations for the same type of headway in station, this part describes the number of different train route combinations for the same type of headway, the maximum, minimum, and average values of headway in different route combinations, and the corresponding bottlenecks, as shown in Tables 9.12–9.15. 5. Analysis of calculation results in Xuzhou East Station The following conclusions can be obtained by analyzing the calculation results of different types of headway in Xuzhou East Station: (1) The headway in station is related to the train operation in sections and the station. The bottleneck of the headway in station may not be located in the station throat but may be located in a block section. Therefore, more reasonable and accurate calculation results can be obtained by taking the station and its adjacent sections as the line study

TABLE 9.12 Headways and bottlenecks with speed combination of 300–300 km/h for Xuzhou East station. Results of combination Operation state

Route combination

Operation direction

Number of combinations

Maximum value (s)

Minimum value (s)

Average value (s)

1

Arrivalarrival

I+I

Same direction

188

189

162

177

2

Arrivalarrival

II + II

Same direction

116

189

163

179

3

Arrivalarrival

I + II

Same direction

308

189

162

179

4

Departuredeparture

I+I

Same direction

188

185

154

174

5

Departuredeparture

II + II

Same direction

116

184

154

166

6

Departuredeparture

I + II

Same direction

308

185

154

169

7

Passingpassing

III + III

Same direction

2

178

171

175

S/N

Bottleneck The 35th block section in the up direction of Suzhou East-Xuzhou East section, the 34th block section in the down direction of Zaozhuang WestXuzhou East section The 1st block section in the up direction of Xuzhou EastZaozhuang West section, the 35th block section in the down direction of Xuzhou East-Suzhou East section The 1st block section in the up direction of Xuzhou EastZaozhuang West section, the 1st block section in the down direction of Xuzhou East-Suzhou East section

8

Arrivalpassing

I + III

Same direction

21

135

45

71

Station throat

9

Arrivalpassing

II + III

Same direction

15

70

39

52

10

Arrivalpassing

II + III

Opposite direction

12

135

62

80

11

Passingarrival

I + III

Same direction

21

262

244

251

12

Passingarrival

II + III

Same direction

15

262

245

251

13

Passingarrival

II + III

Opposite direction

12

193

162

180

Station throat

14

Departurepassing

I + III

Same direction

21

326

305

320

15

Departurepassing

II + III

Same direction

15

326

306

321

The 34th block section in the up direction of Xuzhou EastZaozhuang West section, the 36th block section in the down direction of Xuzhou East-Suzhou East section

The 1st block section in the up direction of Suzhou East-Xuzhou East section, the 27th block section in the down direction of Zaozhuang WestXuzhou East section

Continued

TABLE 9.12 Headways and bottlenecks with speed combination of 300–300 km/h for Xuzhou East station—cont’d Results of combination Operation state

Route combination

Operation direction

Number of combinations

Maximum value (s)

Minimum value (s)

Average value (s)

Bottleneck

16

Departurepassing

II + III

Opposite direction

11

221

211

219

Station throat

17

Passingdeparture

I + III

Same direction

21

93

83

88

18

Passingdeparture

II + III

Same direction

15

93

83

86

The 1st block section in the up direction of Xuzhou EastZaozhuang West section, the 1st block section in the down direction of Xuzhou East-Suzhou East section

19

Passingdeparture

II + III

Opposite direction

11

49

45

45

Station throat

20

Arrivaldeparture

II + II

Opposite direction

–

–

–

–

–

21

Arrivaldeparture

I + II

Opposite direction

64

5

4

5

Station throat

22

Departurearrival

II + II

Opposite direction

88

303

264

284

23

Departurearrival

I + II

Opposite direction

268

304

233

280

S/N

TABLE 9.13 Headways and bottlenecks with speed combination of 350–350 km/h for Xuzhou East station. Results of combination Operation state

Route combination

Operation direction

Number of combinations

Maximum (s)

Minimum (s)

Average (s)

1

Arrivalarrival

I+I

Same direction

188

206

171

187

2

Arrivalarrival

II + II

Same direction

116

205

171

181

3

Arrivalarrival

I + II

Same direction

308

206

171

184

4

Departuredeparture

I+I

Same direction

188

212

177

195

5

Departuredeparture

II + II

Same direction

116

212

179

201

6

Departuredeparture

I + II

Same direction

308

212

178

199

7

Passingpassing

III + III

Same direction

2

186

180

183

S/N

Bottleneck The 34th block section in the up direction of Suzhou East-Xuzhou East section, the 34th block section in the down direction of Zaozhuang WestXuzhou East section The 33rd block section in the up direction of Xuzhou EastZaozhuang West section, the 35th block section in the down direction of Xuzhou East-Suzhou East section The 1st block section in the up direction of Xuzhou EastZaozhuang West section, the 1st block section in the down direction of Xuzhou East-Suzhou East section Continued

TABLE 9.13 Headways and bottlenecks with speed combination of 350–350 km/h for Xuzhou East station—cont’d Results of combination Operation state

Route combination

Operation direction

Number of combinations

Maximum (s)

Minimum (s)

Average (s)

Bottleneck

8

Arrivalpassing

I + III

Same direction

21

155

65

86

Station throat

9

Arrivalpassing

II + III

Same direction

15

80

59

70

10

Arrivalpassing

II + III

Opposite direction

12

155

72

91

11

Passingarrival

I + III

Same direction

21

323

294

306

12

Passingarrival

II + III

Same direction

15

323

294

303

13

Passingarrival

II + III

Opposite direction

12

188

160

175

Station throat

14

Departurepassing

I + III

Same direction

21

419

394

411

15

Departurepassing

II + III

Same direction

15

419

395

413

The 34th block section in the up direction of Xuzhou EastZaozhuang West section, the 36th block section in the down direction of Xuzhou East-Suzhou East section

S/N

The 1st block section in the up direction of Suzhou East-Xuzhou East section, the 1st block section in the down direction of Zaozhuang WestXuzhou East section

16

Departurepassing

II + III

Opposite direction

11

231

221

229

Station throat

17

Passingdeparture

I + III

Same direction

21

85

78

82

18

Passingdeparture

II + III

Same direction

15

85

78

80

The 1st block section in the up direction of Xuzhou EastZaozhuang West section, the 1st block section in the down direction of Xuzhou East-Suzhou East section

19

Passingdeparture

II + III

Opposite direction

11

49

46

46

Station throat

20

Arrivaldeparture

II + II

Opposite direction

–

–

–

–

–

21

Arrivaldeparture

I + II

Opposite direction

64

5

4

5

Station throat

22

Departurearrival

II + II

Opposite direction

88

303

264

284

23

Departurearrival

I + II

Opposite direction

268

304

233

280

TABLE 9.14 Headways and bottlenecks with speed combination of 300–350 km/h for Xuzhou East station. S/N

Operation state

Route combination

Operation direction

1

Arrivalarrival

I+I

2

Arrivalarrival

3

Results of combination

Bottleneck

Number of combinations

Maximum (s)

Minimum (s)

Average (s)

Same direction

188

206

171

187

II + II

Same direction

116

205

171

181

Arrivalarrival

I + II

Same direction

308

206

171

184

4

Departuredeparture

I+I

Same direction

188

264

221

243

5

Departuredeparture

II + II

Same direction

116

264

223

252

6

Departuredeparture

I + II

Same direction

308

264

222

248

7

Passingpassing

III + III

Same direction

2

270

261

266

The 34th block section in the up direction of Suzhou East-Xuzhou East section, the 34th block section in the down direction of Zaozhuang WestXuzhou East section The 33rd block section in the up direction of Xuzhou EastZaozhuang West section, the 35th block section in the down direction of Xuzhou East-Suzhou East section The 33rd block section in the up direction of Xuzhou EastZaozhuang West section, the 34th block section in the down direction of Xuzhou East-Suzhou East section

8

Arrivalpassing

I + III

Same direction

21

155

65

86

Station throat

9

Arrivalpassing

II + III

Same direction

15

80

59

70

10

Arrivalpassing

II + III

Opposite direction

12

155

72

91

11

Passingarrival

I + III

Same direction

21

283

257

267

12

Passingarrival

II + III

Same direction

15

283

258

270

13

Passingarrival

II + III

Opposite direction

12

193

162

180

Station throat

14

Departurepassing

I + III

Same direction

21

471

438

458

15

Departurepassing

II + III

Same direction

15

471

439

463

The 34th block section in the up direction of Xuzhou EastZaozhuang West section, the 36th block section in the down direction of Xuzhou East-Suzhou East section

16

Departurepassing

II + III

Opposite direction

11

231

221

229

The 34th block section in the up direction of Suzhou East-Xuzhou East section, the 31st block section in the down direction of Zaozhuang WestXuzhou East section

Station throat Continued

TABLE 9.14 Headways and bottlenecks with speed combination of 300–350 km/h for Xuzhou East station—cont’d S/N

Operation state

Route combination

Operation direction

17

Passingdeparture

I + III

18

Passingdeparture

19

Results of combination

Bottleneck

Number of combinations

Maximum (s)

Minimum (s)

Average (s)

Same direction

21

93

83

89

II + III

Same direction

15

93

83

87

Passingdeparture

II + III

Opposite direction

11

49

45

45

Station throat

20

Arrivaldeparture

II + II

Opposite direction

–

–

–

–

–

21

Arrivaldeparture

I + II

Opposite direction

64

5

4

5

Station throat

22

Departurearrival

II + II

Opposite direction

88

303

264

284

23

Departurearrival

I + II

Opposite direction

268

304

233

280

The 1st block section in the up direction of Xuzhou EastZaozhuang West section, the 35th and the 1st block sections in the down direction of Xuzhou East-Suzhou East section

TABLE 9.15 Headways and bottlenecks with speed combination of 350–300 km/h for Xuzhou East station. Results of combination Operation state

Route combination

Operation direction

Number of combinations

Maximum (s)

Minimum (s)

Average (s)

1

Arrivalarrival

I+I

Same direction

188

199

173

185

2

Arrivalarrival

II + II

Same direction

116

198

174

184

3

Arrivalarrival

I + II

Same direction

308

199

173

185

4

Departuredeparture

I+I

Same direction

188

185

152

172

5

Departuredeparture

II + II

Same direction

116

184

152

162

6

Departuredeparture

I + II

Same direction

308

185

152

166

7

Passingpassing

III + III

Same direction

2

248

234

241

S/N

Bottleneck The 13th block section in the up direction of Suzhou East-Xuzhou East section, the 14th block section in the down direction of Zaozhuang WestXuzhou East section The 1st block section in the up direction of Xuzhou EastZaozhuang West section, the 1st block section in the down direction of Xuzhou East-Suzhou East section The 2nd block section in the up direction of Suzhou East-Xuzhou East section, the 2nd block section in the down direction of Zaozhuang WestXuzhou East section Continued

TABLE 9.15 Headways and bottlenecks with speed combination of 350–300 km/h for Xuzhou East station—cont’d Results of combination Operation state

Route combination

Operation direction

Number of combinations

Maximum (s)

Minimum (s)

Average (s)

Bottleneck

8

Arrivalpassing

I + III

Same direction

21

135

45

71

Station throat

9

Arrivalpassing

II + III

Same direction

15

70

39

52

10

Arrivalpassing

II + III

Opposite direction

12

135

62

80

11

Passingarrival

I + III

Same direction

21

376

341

357

12

Passingarrival

II + III

Same direction

15

376

341

352

13

Passingarrival

II + III

Opposite direction

12

188

160

175

Station throat

14

Departurepassing

I + III

Same direction

21

279

265

275

15

Departurepassing

II + III

Same direction

15

278

265

274

The 7th block section in the up direction of Xuzhou EastZaozhuang West section, the 10th block section in the down direction of Xuzhou East-Suzhou East section

S/N

The 1st block section in the up direction of Suzhou East-Xuzhou East section, the 1st block section in the down direction of Zaozhuang WestXuzhou East section

16

Departurepassing

II + III

Opposite direction

11

221

211

219

Station throat

17

Passingdeparture

I + III

Same direction

21

85

78

82

The 1st block section in the up direction of Xuzhou EastZaozhuang West section, the 1st block section in the down direction of Xuzhou East-Suzhou East section

18

Passingdeparture

II + III

Same direction

15

85

78

80

19

Passingdeparture

II + III

Opposite direction

11

49

46

46

Station throat

20

Arrivaldeparture

II + II

Opposite direction

–

–

–

–

–

21

Arrivaldeparture

I + II

Opposite direction

64

5

4

5

Station throat

22

Departurearrival

II + II

Opposite direction

88

303

264

284

23

Departurearrival

I + II

Opposite direction

268

304

233

280

358

9. Mechanism of enhancing the carrying capacity

range and taking into account the train operation in sections and the station. (2) The headway in station varies under different combinations of train operating speeds. The train operating speed determines the operation curve of the train in a section to a great extent, and the train occupation time in the train occupation unit will also change accordingly, thus affecting the minimum headway of adjacent trains. Therefore, it is meaningful to consider the combination of train speeds over sections in the calculation of headway in station. The operation curve of the train in the station is mainly limited by the diverging speed permitted on turnouts and the allowable passing speed of the main track, and less limited by train operating speed. For example, the bottleneck of headway in station for arrival-departure is located in the station throat, and its value does not change with the combination of train operating speeds. (3) Under the same combination of train operating speeds, the value of headway in station is affected by the combination of train routes. There may be many combinations of routes of adjacent trains according to the basic route set of the station (see Table 9.1). The “Route Combination” column in Tables 9.12–9.15 shows the number of route combinations under different types of headway in station, and the maximum, minimum, and average values of headway in station in different route combinations. The headway in station is not fixed under the same train speed combination, due to differences in the route conflict area, route length, and other factors. (4) In the segmentation release mode, after the preceding arrival train ceases occupying the route conflict area, the establishment of the route for the following train can be started, and it is not necessary to wait until the tail of the preceding train runs past the reverse departure signal on the arrival and departure track. Therefore, the proposed calculation method for headway in station is more in line with the route setting rules of high-speed railway trains.

References [1] B. Han, P. Liu, Dynamic Evolution of Headway and Critical Block Section on High-Speed Railway, ASCE, Reston, VA, USA, 2018. [2] P. Liu, Study on Capacity Calculation and Improvement Based on Refined Research of Headway in Stations for High Speed Railway, Beijing Jiaotong University, 2019.

C H A P T E R

10 Principle of improving the carrying capacity of high-speed railway by adopting segmentation release mode 10.1 Overview of block section and train route 10.1.1 Development history of release modes for block section and train route This chapter puts forward measures to enhance the carrying capacity of high-speed railways based on the segmentation release mode for block sections with two or more track circuits and train routes in stations from the perspective of shortening the headways in station. The factors influencing the carrying capacity mainly include the structure of train operation and the headway in station as mentioned in this book. The carrying capacity can be improved from the following two aspects: (1) optimizing the structure of train operation, such as reducing the speed difference between different speed levels, adjusting the proportion of trains in terms of speed level and optimizing the stop schedule plan; and (2) shortening the headway. The main methods to shorten the headway include upgrading the signal system (see Part I of this book) and optimizing the station transportation organization mode. In Chapter 8, the precise calculation of headways in station in the case of different train operation status, train route types and operation direction combinations is introduced to reduce the headways in station. In addition, the release conditions of block sections and the inbound routes of adjacent trains can also be optimized to further reduce the headways in station, thus improving the station carrying capacity.

Theory and Technology for Improving High-Speed Railway Transportation Capacity https://doi.org/10.1016/B978-0-323-99700-3.00006-2

359

Copyright © 2023 Elsevier Inc. All rights reserved.

360

10. Development history of release modes

Due to fast speed and large mass of railway trains, the braking distance is much longer than the visual distance, which poses a hidden danger to railway operation safety. To avoid rear-end collision in the same direction and head-on collision in the opposite direction between trains, reasonable setting of the headway under the condition of ensuring the railway operation safety can effectively improve the railway carrying capacity. There are two main methods for maintaining the headway, namely the spaceinterval method and the time-interval method. According to the provisions of the Regulations of Railway Technical Operation (High-Speed Railway) in China, the two methods are defined respectively as follows [1]: • The space-interval method refers to a method in which two trains take the section divided by the station and the block post or the block section divided by the block signal of the automatic block as the headway. That is, under normal circumstances, only one train is allowed to occupy each section (or block section) at the same time. • The time-interval method, also known as the interval continuation method, means that after each train is departed, the next train is departed at a certain interval to prevent trains from colliding. Before the 1840s, the train operation safety was guaranteed by the “time-interval method.” In 1842, the “space-interval method” was invented in Britain, and it has been widely used in the world since then to ensure the train operation safety and improve the carrying capacity of the line. This method requires that the line be divided into continuous and nonoverlapping parts (also called block sections), each of which is allowed to be occupied by only one train at the same time. Block section falls into manual block section, semiautomatic block section, automatic block section, quasimoving block section and moving block section according to the evolution of its release mode in sequence. • Manual blocking, including telegraph blocking, telephone blocking, electric staff blocking and electric tablet blocking, refers to a blocking mode in which the running position of the train is recorded and the color-light signal is controlled manually. Before departure, the receiving and departure stations or block posts jointly confirm that the block section is clear, and then the departure station or block post records that this section has been occupied by using the train-staff instrument, tablet, clearance card, etc., and informs the receiving station or block post of the occupation information by telephone, telegram and other means. Before the train arrives, the departure station shall prevent the following trains from entering the section, and the receiving station shall also prevent the trains running in reverse direction from entering this section.

10.1 Overview of block section and train route

361

• Semiautomatic blocking refers to a blocking mode in which the clearance of the section is confirmed manually, and the track circuit automatically sets the section to the occupied state upon judging that the train enters the section after departure. After the train enters the section, the track circuit will implement interlocking control on the color-light signal to notify the two stations of the occupation information. After the arrival of the train, it is still necessary to manually check the marshaling integrity of the arrival train and restore the section state to the clear state. • Automatic blocking refers to a blocking mode in which the block signal is used to divide the section into several block sections equipped with track circuits through which displays of the train and the signal are connected, so that the display of the signal may change automatically with the train operation position. At the starting end of each block section, a color-light block signal for protecting the section is set. The signal displays a green light in normal times, and only when the train occupies the block section (or a rail breakage occurs) will it automatically display a red light, to require the following train to stop. • Quasimoving blocking refers to a blocking mode in which the section occupation and information transmission are judged by telegraph track circuits assisted by balises. Telegraph track circuits and balises can inform the following trains of the distance to continue to go. The following trains can reasonably slow down or brake based on this distance. The starting point of train braking can be extended to a place where the safe braking can be ensured, so as to improve the speed control of the train and reduce the safe headway to improve the utilization efficiency of the track. • Moving blocking refers to a blocking mode in which on-board equipment and trackside equipment are used to realize uninterrupted two-way communication based on the modern radio technology, so that the control center can dynamically calculate the maximum braking distance of the train according to the status information such as realtime speed and position, and transmit relevant information (such as the position of the preceding train and movement authority) to the train through trackside equipment to ensure the safe distance before and after the train. For a track in this blocking mode, the section division on the physical level is canceled. The moving block section consists of a certain number of preset units, and the number of the units can vary with the speed and position of the train. This mode is the developing trend of railway blocking mode in the future. Train route refers to a section of line passed by (prepared for) a train running (moving) from one location to another in a district such as a station and a spurline. Train route is one of the important factors affecting the

362

10. Development history of release modes

headway. The route combination of adjacent trains determines the existence of operation conflict, the track circuit district with operation conflict, and the operation process of trains in the station. If adjacent trains are in parallel routes, there is no operation conflict. If the routes of adjacent trains cross or overlap and conflict with each other, it is necessary to define the minimum headway among the arrival, departure or passing time of such trains. At the same time, the longer the track circuit district with operation conflict, the longer time it will be occupied, resulting in larger headway and lower carrying capacity. The station route setting and release times are also the composition elements of the headway in station. When the station signal, interlocking, and block equipment are improved, the headway will be shorter, and the carrying capacity will be greater. The current station route setting rules provide that before the interlocking system establishes a route, all track circuits on the route must be clear, the turnouts on the route are in the correct position, and no conflicting route is established. In the same route protected by the signal, it is not allowed to operate two or more trains simultaneously. In addition, the segmentation release mode is widely applied for routes of stations. In this mode, tracks circuits are released segment by segment as the train travels. By improving the station route setting rules, it is helpful to reduce the headway and enhance the carrying capacity.

10.1.2 Practice in block sections and train routes of high-speed railways in China In view of the technical characteristics of high-speed railways, the current relevant operation rules, technical specifications and basic theories of block sections and train routes in China are introduced as follows. 10.1.2.1 Blocking mode for high-speed railways in China The equipment level of the train operation control system is determined according to the allowable speed of the line. China’s current high-speed railway standard, the Regulations of Railway Technical Operation (HighSpeed Railway), stipulates that the CTCS-2 train control system is suitable for railways below 250 km/h, and the CTCS-3 train control system should be adopted for railways at 250 to 300 km/h or above [1]. As the blocking modes of CTCS-2 and CTCS-3 train control systems are quasimoving blocks, China’s high-speed railways adopt the quasimoving blocking mode. In this mode, the following target point of the following train is the starting end of the block section occupied by the preceding train, and a certain safety protection distance is reserved, as shown in Fig. 10.1.

10.1 Overview of block section and train route

FIG. 10.1

363

Schematic diagram of braking distance.

The start location in Target Speed Monitoring Section (TSM, the calculation point for a following train to perform braking from the maximum speed) is determined by calculation according to target distance, target speed and the performance of the train. Therefore, the target point is relatively fixed and will not change due to the running of a preceding train in the same block section, while the start location in the TSM varies with the line parameters and the performance of the train, and the space interval between adjacent trains is not fixed. 10.1.2.2 Rules for train operation organization in high-speed railway sections in China According to the relevant regulations for train operation organization of sections in China, the process of train operation in the section has the following characteristics: • The same block section is only allowed to be occupied by just one train. • If there are two or more track circuits in one block section at the same time, all the track circuits in this block section will be occupied by the train at the same time, while other trains cannot occupy any of these track circuits at the same time. • Each track circuit has the function of checking the occupation by the train, and the track circuits occupied in the block section are released one by one by the train. 10.1.2.3 Station route setting and release rules of high-speed railways in China According to the station route setting and release rules in China, the train operation process in stations has the following characteristics: • In the same route protected by the signal, it is not allowed to operate two or more trains simultaneously. Specifically, the protection range of a departure signal covers the district from the departure signal to the first departure signal.

364

10. Development history of release modes

• Before the train route is established, all track circuits on the route must be clear, the turnouts on the route are in the correct positions, and no conflicting route is established. • The segmentation release mode is generally applied for routes of stations. In this mode, tracks circuits in the route are released segment by segment as the train travels.

10.1.2.4 Movement authority of train control system of high-speed railways in China (1) Generation of movement authority for CTCS-2 train control system The onboard equipment of the CTCS-2 train control system shall identify the end of movement authority (MA) according to the information of track circuits and balises. The coding information of track circuits is an important basis for determining the train operation position and is provided by the train control center (TCC) equipment. The correspondence between track circuit code and train control equipment display is shown in Table 10.1. TABLE 10.1 Correspondence between track circuit code and train control equipment display. Signal

Code

Meaning

L5

L5

One green light with “5”

L4

L4

L3

Signal

Code

Meaning

U2

U2

One yellow light with “2”

One green light with “4”

U

U

One yellow light

L3

One green light with “3”

UUS

UUS

One flash with double halfyellow

L2

L2

One green light with “2”

UU

UU

One light with double halfyellow

L

L

One green light

HB

HB

One flash with half-yellow and half-red

LU

LU

One light with half-green and half-yellow

HU

HU

One light with half-yellow and half-red

U2S

U2S

One yellow flash with “2”

H

H

One red light

10.1 Overview of block section and train route

365

According to the Technical Specification for Train Control Center, the coding principles for track circuits in sections and at stations of the train control center are as follows [2]: 1. Coding principles of track circuits in sections For the section track segment, the TCC shall send codes according to the track circuit tracking code sequence on the basis of the occupation status of the front track segment and the clearing status of the receiving signal of the front station, as shown in Fig. 10.2. The code values of block sections in the direction opposite to the train operation direction are HU, U, LU, L, L1, L2, L3, L4, L5, L5… in turn. 2. Coding principles of track circuits at stations ① After the train receiving route signal is clear, relevant track circuits of the receiving route send codes according to the status of the departure signal, and the codes sent by track circuits from the home signal to the departure signal are consistent, that is, the code values of all track circuits on the receiving route are the same. In addition, the inbound approach district sends codes according to the status of the home signal. For example, when the turnouts of the smallest number on the receiving route on the diverging track are #18 or above, and there is no fixed or temporary speed limit lower than 80 km/h on the receiving route, the track circuit coding is shown in Fig. 10.3 under the condition that the home signal is clear and the departure signal is off. The code value is HU for relevant track circuits on the train receiving route, or UUS for the inbound approach district. ② After the train departure route signal is clear, relevant track circuits of the departure route send codes according to the code sending status of the first departure block section in the departure direction, and the codes sent by track circuits from the departure signal to the rear end of the first departure block section are consistent, that is, the code values of all track

FIG. 10.2

Coding of track circuits in sections.

FIG. 10.3

Track circuit coding after clearance of train receiving route signal.

366

10. Development history of release modes

circuits on the departure route and the first departure block section are the same. In addition, the track circuits in front of the departure signal send codes according to the departure signal status and the code sending status of the first departure block section in the departure direction. For example, when the turnouts of the smallest number on the departure route on the diverging track are #18 or above, and there is no fixed or temporary speed limit lower than 80 km/h on the departure route, the track circuit coding is shown in Fig. 10.4 under the condition that the train occupies the second departure block section and the departure signal is clear. The code value is HU for relevant track circuits on the departure route and the first departure block section, or UUS for the track circuits in front of the departure signal. ③ After the train through route signal is clear, the train through route is divided into two parts: the receiving route and the departure route. The receiving route sends codes according to the status of the departure signal and the code values of all track circuits on the receiving route are the same. The departure route sends codes according to the code sending status of the first departure block section in the departure direction, and the code values of all track circuits on the departure route and the first departure block section are the same. If the track circuit between the home signal and the departure signal is regarded as a “block section” and so is the track circuit between the departure signal and the rear end of the first departure block section, the code sending principle is the same for the train through route and the track circuit in the section. For example, when the train occupies the second departure block section, the track circuit coding is shown in Fig. 10.5. The code value is HU for relevant track circuits on the departure route and the first departure block section, U for relevant track circuits on the receiving route, or LU for the inbound approach district.

FIG. 10.4

Track circuit coding after clearance of train departure route signal.

FIG. 10.5

After clearance of train through route signal.

10.1 Overview of block section and train route

FIG. 10.6

367

Headway in block section after optimization.

④ When the train enters the corresponding train route, and the train route is established, the track segment will send the detection code after the track circuit in front of a track circuit running on the route is occupied or this track circuit is released. For example, in Fig. 10.6, 5-13DG starts sending the detection code when the train occupies IG or 5-13DG is released. To sum up, the train control center’s coding principles for track circuits in sections and at stations have the following characteristics: • In a section, the block section sends codes according to the occupation status of the front track segment and the clearing status of the receiving signal of the front station, while the code values of different track circuits in the same block section are the same. • In the station, the receiving route sends codes according to the status of the departure signal and the code values of all track circuits on the receiving route are the same. The departure route sends codes according to the code sending status of the first departure block section in the departure direction, while the code values of all track circuits on the departure route and the first departure block section are the same.

(2) Generation of movement authority for CTCS-3 train control system In the CTCS-3 train control system, the radio block center (RBC) generates control information such as the train movement authority according

368

10. Development history of release modes

to the information provided by interlocking equipment, temporary speed restriction server, adjacent RBCs, centralized traffic control (CTC) equipment and on-board equipment, and sends such control information to on-board equipment through radio communication, so as to control the safe train tracking operation. Specifically, the position of the preceding train is transmitted by the RBC to the following train through radio communication, and the track circuit is only used to check the track occupation. In the section, the RBC receives the location report and other information sent by on-board equipment through GSM-R. In the station, according to the RBC-CBI Interface Specification [3], the RBC interfaces with the CBI (Computer-based Interlocking) through the signal safety data network, and the CBI provides it with information on station track circuits and train routes: • Information on station track circuits: refers to the state information of all station track circuits transmitted to and controlled by the RBC according to the occupied or unoccupied state. • Information on train routes: refers to the state information of train routes in the station controlled by computer interlocking, including five states: nonactivated, unavailable, normal, passing, and guiding. Among them, “nonactivated” means that the train route is not set and the corresponding signal authorization cannot be used; “unavailable” means that although the train route has been locked, the normal and guiding signals are not clear, and the signal authorization cannot be used due to signal failure, conflicting route, delay cancelation or other reasons; “normal” means that all conditions of the train route have been met, the signal is normally clear and the signal authorization can be used; “passing” means that the train is running on the route, the route is being released, and the corresponding signal authorization is unavailable to other trains; “guiding” means that the train route is established in a special way, and the corresponding signal authorization can be used under certain restrictions.

10.1.3 Optimization methods for existing block sections and train routes It is of great significance to study how to improve the carrying capacity for the high-speed railway network with insufficient capacity. For the European railway network, due to the relative surplus capacity, there is no urgent need to improve its carrying capacity. In Japan, because of its long and narrow territory, as well as no complex high-speed railway network, the way to improve the carrying capacity is relatively simple. However, it is very difficult to improve the capacity of China’s high-speed

10.2 Overview of segmentation release mode

369

railways because of their supercomplex network and huge demand, which has also become the focus of China’s high-speed railway research. Optimization of block sections and train routes is an important part of the method set for improving the carrying capacity of high-speed railways. In terms of block section optimization, Zhang et al. modified the coding rules of track lines under the existing CTCS-3 train control system to automatically change the low frequency codes of two track circuits in the block section, thus realizing the dynamic division of the fixed block section. As shown in Fig. 10.6, the dynamic division of track circuits in block sections containing multiple track circuits can reduce the headway, thus shortening the following time in a section and improving the carrying capacity [4]. In terms of train route optimization, Wang et al. put forward the optimization problem of the routes in the variable locking section near the station, and established the calculation model of the variable locking section and route trigger. By using the above method, the headway can be further shortened, so as to improve the carrying capacity of stations and adjacent sections [5]. The above-mentioned existing research mainly discusses the method of shortening the headway from the aspect of signal system, and the related detailed introduction is shown in the first part of this paper. This part will focus on the influence of the segmentation release mode on the capacity of the train occupation units in stations and adjacent sections during transport organization.

10.2 Overview of segmentation release mode 10.2.1 Concept of segmentation release mode Segmentation release mode for the block sections: The train occupation unit is the minimum line unit occupied by a train during its operation on the line. In a section, the train occupation unit is the track circuit, and a block section may contain a track circuit or multiple track circuits one after another that neither overlap nor isolate. According to the existing rules for train operation organization in China, the starting time of the train occupation time for track circuits in the same block section is the same. Occupation of different track circuits in the same block section begins at the same time, and other trains can begin to occupy a block section only after all track circuits in it are clear of the preceding train. The segmentation release mode for the block sections with two or more track circuits means that different track circuits are opened in segments and not occupied by the train at the same time. Only after a track circuit is clear of the preceding train is it open to other trains, as shown in Fig. 10.7. The segmentation release mode for the block sections equates to treating track circuits in

370

FIG. 10.7

10. Development history of release modes

Schematic diagram of segmentation opening mode for block sections.

the same block section as independent block sections. Due to the large number of block sections on the high-speed railway, segmentation may be made, in combination with the bottleneck of the headway in station, in some block sections, especially those adjacent to stations. Segmentation release mode for the routes: In the station, the train occupation unit is the minimum block section in station. According to the station route setting rules, the starting time of the train occupation time for the minimum block sections in station on the same route is the same. Before the computer interlocking system establishes a route, all track circuits on the route must be clear, all turnouts on the route must be in the correct position, and no conflicting route shall be established. In the same route protected by the signal, it is not allowed to operate two or more trains simultaneously. Although train routes are in the segmentation release mode, other trains can only occupy the train operation conflict area with proper routes established after all minimum block sections in station within the train operation conflict area are clear. For a specific train route, the segmentation release mode means that during the route setting, the requirement of “all track circuits on the route must be clear” is exempted, but efforts shall be made to check whether the turnout is correctly positioned or can be operated to the specified position, and no conflicting route is established. At present, the moving block is used for the CBTC system of urban rail transit, and the computer interlocking system adopts these station route setting rules. Only after a minimum block section in station is clear of the preceding train is it open to other trains.

10.2.2 Necessity analysis of segmentation release mode The effect of reduced headways in station is analyzed, which shows that according to the train operation organization rules of section and the station route setting rules, the starting time of the train occupation time for track circuits in the same block section is the same, and the starting time of the train occupation time for the minimum block sections in station on the same route is the same. Fig. 10.8 shows the changes in the minimum

FIG. 10.8

Changes in minimum headway between adjacent trains. (Continued)

FIG. 10.8, CONT’D

10.2 Overview of segmentation release mode

373

headway between adjacent trains when segmentation release mode is applied to block sections (including two or more track circuits) and station train routes, and the train occupation units 2, 3 and 4 are located in the same block section or route. Fig. 10.8A shows the train tracking operation before segmentation release mode is applied to the block sections and the train routes. Train occupation units 2, 3, 4 are identical in terms of the starting time of the train occupation time, but the continuous time in the train occupation time is longer in train occupation units 3 and 4. The second train can begin to occupy the train occupation unit 2 only after the first train ends its occupation of the train occupation unit 4. Fig. 10.8B shows the train tracking operation after segmentation release mode is applied to the block sections and the train routes. The starting time of the train occupation time of train occupation units 3 and 4 depends on the actual operating position of the train, and the braking time replaces the continuous time. A train occupation unit is open to the second train once the first train ends its occupation of this train occupation unit. By comparison, it is found that after segmentation release mode is applied in block sections and routes, the train occupation time of train occupation units 3 and 4 is cut down, and thereby the headways in station are reduced. In fact, the release of a train occupation unit to the second train does not mean that the second train will immediately occupy or enter this train occupation unit. First, whether the second train immediately occupies the train occupation unit depends on the bottleneck. As shown in Fig. 10.8B, the train occupation unit 4 is the bottleneck, and thus the second train can only begin occupation after the first train in the train occupation unit 4 ends its occupation. Second, before the train enters a track circuit or a minimum block section in station, the occupation time also includes preparation time, reaction time and braking time. The preparation time and the reaction time have fixed and small values, while the braking time has large values, which are closely related to the braking distance, and is an important factor to ensure the train operation safety. The braking distance and the throat length are analyzed. When a train is followed by another train in a station, if the first train stops suddenly and accidentally, it must be ensured that the second train can be braked and stopped in time without collision. Therefore, the space interval between adjacent trains must be greater than the braking distance of the second train at the current operating speed. The braking distance of the train varies with the EMU model, train speed and braking level. #18 turnout is used at most stations to connect the main track and the arrival and departure tracks, and the diverging speed permitted on turnouts is 80 km/h. Assuming that the station is located on a straight track, the braking distance and time required for CRH1, CRH2, CRH3, CRH380B EMUs at operating speeds less than 80 km/h and different service braking levels can be

374

10. Development history of release modes

calculated using the train traction calculation theory. The calculation results are shown in Fig. 10.9. It can be seen from Fig. 10.9 that the lower the train speed, the shorter the braking distance required. If the initial operating speed of trains is 80 km/h • When a high braking level is adopted (e.g., Level 7 service braking), the four models of EMUs (CRH1, CRH2, CRH3, CRH380B) will require a braking distance of 414.86 m, 350.99 m, 452.15 m and 374.23 m respectively, the maximum braking distance being 452.15 m. • When a medium braking level is adopted (e.g., Level 4 service braking), the four models of EMUs will require a braking distance of 685.03 m, 564.77 m, 896.59 m and 543.31 m respectively, the maximum braking distance being 896.59 m. • When a low braking level is adopted (e.g., Level 1 service braking), the four models of EMUs will require a braking distance of 1796.74 m, 1465.35 m, 1799.10 m and 2377.23 m respectively, the maximum braking distance being 2377.23 m. Yards of large and medium-sized high-speed railway stations generally are characterized by a large number of arrival and departure tracks and complex, long throats reaching more than 1000 m. For adjacent departure trains, according to the current station route setting rules, a departure route can only be set for the second train after the first departure train ceases occupying the first departure block section (approximately 800–1500 m long), resulting in a redundant headway reserved for such adjacent trains. As the EMU braking performance continuously improves, it is more necessary to properly shorten the headway between adjacent trains and improve the arrival and departure efficiency of station throats. Allowing two or more trains to follow more closely by releasing the train route in segments can therefore help shorten the headways in station and improve the carrying capacity.

10.2.3 Feasibility and safety analysis of segmentation release mode The track circuit is used to check the track occupation in the case of the CTCS-2 train control system. The code value of track circuit indicates whether the track circuit is clear within a certain length of line ahead of the train. In combination with the code values, length and other data of track circuits, the train control system can determine the following target point and generate the movement authority. According to the braking performance of the train, the train control system deduces the distance-to-go speed mode control curve from the target point, as shown in Fig. 10.10.

2000.00

1600.00 1465.35

1796.74

1200.00 Braking distance of CRH2 (m)

Braking distance of CRH1 (m)

1500.00

Weak braking

1000.00

Medium-forced braking 685.03

Force braking

Weak braking 800.00 Medium-forced braking 564.77 Force braking 400.00

500.00

350.99 414.86

0.00 0.00

0.00 0.00

20.00

40.00 60.00 Train speed (km/h)

20.00

80.00

2000.00

40.00 60.00 Train speed (km/h)

2500.00

80.00

2377.23

1799.10

2000.00

1000.00

896.59

Weak braking Medium-forced braking Force braking

Braking distance of CRH380B (m)

Braking distance of CRH3 (m)

1500.00

1500.00 Weak braking Medium-forced braking 1000.00

Force braking

543.31

500.00 452.15

500.00 374.23

0.00

0.00 0.00

20.00

40.00 60.00 Train speed (km/h)

80.00

0.00

20.00

40.00 60.00 Train speed (km/h)

FIG. 10.9 Braking distances for different models of emus within operating speed of [0,80] km/h.

80.00

376

FIG. 10.10

10. Development history of release modes

Generation of distance-to-go speed mode control curve by CTCS-2 train con-

trol system.

The train control system controls the train according to the distance-to-go curve. As the train travels, the following target point is continuously updated, and the distance-to-go curve is updated accordingly. When the preceding train stops abruptly due to a sudden failure, the following train can be braked and stopped safely following the distance-to-go curve to ensure no collision with the preceding train. It can be seen that generating a reliable movement authority in a timely manner is essential to ensure operation safety. According to the movement authority, the train control system can calculate the distance-to-go curve to avoid rear-end collision of adjacent trains. In the CTCS-2 train control system, the code value of track circuit is a key factor in determining the movement authority. According to the track circuit coding rules in 9.1.2, in sections, different track circuits in the same block section have the same code value; in stations, all track circuits on the receiving route have the same code value, and the departure route and the first departure block section have the same code value. To realize segmentation release of block sections and routes at stations, it is necessary to adjust the train control center’s coding principle for track circuits in sections and at stations, or add section block signals and station route signals to distinguish the code values of different track circuits in the same block sections and receiving and departure routes at stations, which allows the train control system to update target

10.2 Overview of segmentation release mode

377

points and generate the movement authority in time. The CTC system is used for train operation command on the high-speed railway, and it realizes centralized control of signal equipment in districts as well as direct command and management of train operation. To realize segmentation release of block sections and routes at stations, it is necessary to adjust the decentralized and self-regulated CTC system to allow the train to take the track circuit as the train occupation unit in sections and at stations. In particular, for setting the station train routes, the station autonomous controlling computer only needs to check that the turnouts on the train route are in the correct position and locked and no conflicting route is established, and does not need to check that all track circuits in the train route are clear. In addition, data information on temporary speed restriction servers, balises, and other equipment needs to be modified and improved. The track circuit is used to check the track occupation in the case of the CTCS-3 train control system. The radio block center (RBC) determines the following target point and generates the movement authority based on information provided by the computer interlocking system, on-board train control equipment, etc., and sends it to the on-board equipment via radio communication. Specifically, the position of the preceding train is transmitted by the RBC to the following train via radio communication. The train control system deduces the distance-to-go speed mode control curve from the target point to control the safe train tracking operation, as shown in Fig. 10.11. Similar to the CTCS-2 train control system, generating a reliable movement authority in a timely manner is essential to ensure operation safety. In the CTCS-3 train control system, the information provided to the RBC by the on-board equipment, computer interlocking system, etc. is a key factor in determining the movement authority. To realize segmentation release of block sections and routes at stations, the RBC needs to generate the movement authority in track circuits for the following train after receiving the position information of the preceding train, so that the train control system can update the target point and generate the movement authority in time. Also similar to the CTCS-2 train control system, it is necessary to emphatically adjust the station route setting rules and relevant data information of the RBC, temporary speed restriction server and other equipment of the decentralized and selfregulated CTC system. Based on the above analysis, it is found that the CTCS-2 and CTCS-3 train control systems meet the requirements of segmentation release mode and provide a reference for the future technical development direction. However, during their implementation at this stage, it is necessary to adjust the operation rules and data storage of relevant equipment, which involves a wide range and has great difficulties. In future research, it is necessary to propose more practicable measures in combination with the actual situation of high-speed railways.

378

FIG. 10.11

10. Development history of release modes

Generation of distance-to-go speed mode control curve by CTCS-3 train con-

trol system.

10.3 Calculation and adjustment of headway in station in segmentation release mode 10.3.1 Adjustment of time-space graph of train tracking operation When segmentation release mode is applied to the block sections and the train routes, the train occupation time and the train operation conflict area change, so the precise calculation method for headway in station proposed in Chapter 8 needs to be revised accordingly. (1) Train occupation unit: The division of the train occupation units remains unchanged after segmentation release mode is applied to the block sections and the train routes. (2) Train occupation time: The train occupation time is composed of preparation time, reaction time, braking time, running time, clearing time and closing time after segmentation release mode is applied to the block sections and the train routes, and there is no continuous time. In addition, the starting time of the train occupation time depends on the actual operating position of the train. In a section, for the block section in segmentation release mode, the continuous time in the train

10.3 Calculation and adjustment of headway in station in segmentation release mode

379

occupation time of the second and subsequent track circuits in this block section becomes the braking time, which is calculated according to the operating speed of the train when it enters the train occupation unit. At a station, when the station sets the train route after the train route is in segmentation release mode, it is not necessary for all track circuits on the route to be clear, and two or more trains are allowed to run in the train tracking mode in the station throat. It is not necessary for all the minimum block sections in station on the train route to be occupied by trains at the same time, and the continuous time in the train occupation time of the second and subsequent minimum block sections in station on the train route becomes braking time. (3) Train operation conflict area: The train operation conflict area becomes the train occupation unit after segmentation release mode is applied to the block sections and the train routes. For the block section in segmentation release mode, the train operation conflict area becomes the track circuit instead of the block section; for the train route in segmentation release mode, the train operation conflict area becomes the minimum block section in station. (4) Adjusted time-space graph of train tracking operation in section: After segmentation release mode is applied to the block sections, the time-space graph of train tracking operation in section needs to be adjusted. In order to avoid the train operation conflicts, the track circuit can be occupied by other trains after it is released by the preceding train. There are two track circuits in the block section 4 in Fig. 10.12, and the starting time of train occupation of these two track circuits is same. After segmentation release mode is applied to the block section 4, the starting time of train occupation of the two track circuits is different, and the continuous time in the train occupation time of the second track circuit becomes braking time, as shown in Fig. 10.13. The first track circuit in the block section 4 can be occupied by the following train after it is released by the preceding train. (5) Adjusted time-space graph of train tracking operation in station: After segmentation release mode is applied to the train routes, the description of the train tracking operation in station also needs to be adjusted. In order to avoid the train operation conflicts, in the route conflict area, one minimum block section in station can be occupied by other trains after it is released by the preceding train, so it is not necessary to wait for the preceding train to release all the minimum block sections in station. Taking the adjacent arrival trains and departure trains in the same direction and with route combination I + I as examples, the time-space graph of train tracking operation illustrating the occupation of the transport capacity resources is adjusted to Figs. 10.15 and 10.17. Compared with Fig. 10.14, the starting time of occupation of the minimum block sections 1, 2, 3 and 4

FIG. 10.12

Following operation process of adjacent trains in section.

FIG. 10.13

Following operation process of adjacent trains in section.

382

10. Development history of release modes

in station in Fig. 10.15 is different, and it depends on the actual operating position of the train, and the continuous time in the occupation time of the minimum block sections 2, 3 and 4 in station becomes braking time. The minimum block section 2 in station can be immediately occupied by the following train after the preceding train ceases occupying it. Compared with Fig. 10.16, the starting time of occupation of the minimum block sections 1, 2 and 3 in station and the first departure block section in Fig. 10.17 is different, and the continuous time in the occupation time of the minimum block sections 2 and 3 in station and the first departure block section becomes braking time. The minimum block section 2 in station can be immediately occupied by the following train after the preceding train ceases occupying it. The time-space graph of train tracking operation corresponding to other types of headways in station can be analogized, and thus, it’s not detailed here.

10.3.2 Reconstruction calculation model of headway in station The calculation model of headway in station also needs to be adjusted [6]. For the model established in Section 8.3.1, since the train occupation units in a block section do not need to be opened at the same time, the continuous time in the occupation time of the second and subsequent train occupation units in the block section or train route needs to be changed into braking time. Therefore, Eqs. (9.16)–(9.25) in the constraint of “the second and subsequent train occupation units in the block section or train route” are changed into Eqs. (10.1)–(10.12), and Eqs. (8.26)–(8.27) in the constraint of “correlation between the occupation time of different train occupation units” are deleted. Section: birea,qr ¼ biqr + tirou,qr ,8if1, 2g,8qr Qr+ ,8rR

(10.1)

biapp,qr ¼ birea,qr + tirea,qr ,8if1, 2g,8qr Qr+ ,8rR

(10.2)

biocc,qr ¼ biapp,qr + tiapp,qr ,8if1, 2g,8qr Qr+ ,8rR

(10.3)

bicle,qr ¼ biocc,qr + tiocc,qr ,8if1, 2g,8qr Qr+ ,8rR

(10.4)

birel,qr ¼ bicle,qr + ticle,qr ,8if1, 2g,8qr Qr+ ,8rR

(10.5)

eiqr ¼ birel,qr + tirel,qr ,8if1, 2g,8qr Qr+ ,8rR

(10.6)

FIG. 10.14

Following operation process of adjacent arrival trains in station.

FIG. 10.15

Following operation process of adjacent arrival trains in station.

FIG. 10.16

Following operation process of adjacent departure trains in station.

FIG. 10.17

Following operation process of adjacent departure trains in station.

10.3 Calculation and adjustment of headway in station in segmentation release mode

387

Station: birea,qsta ¼ biqsta + tirou,qsta ,8if1, 2g,8qsta Qsta +

(10.7)

biapp,qsta ¼ birea,qsta + tirea,qsta ,8if1, 2g,8qsta Qsta +

(10.8)

biocc,qsta ¼ biapp,qsta + tiapp,qsta ,8if1, 2g,8qsta Qsta +

(10.9)

bicle,qsta ¼ biocc,qsta + tiocc,qsta ,8if1, 2g,8qsta Qsta +

(10.10)

birel,qsta ¼ bicle,qsta + ticle,qsta ,8if1, 2g,8qsta Qsta +

(10.11)

eiqsta ¼ birel,qsta + tirel,qsta ,8if1, 2g,8qsta Qsta +

(10.12)

10.3.3 Effect of segmentation release mode on improving station carrying capacity According to the analysis of the headway in station in Chapter 8 and this chapter, we can find that the reduction of the headway in station after segmentation release mode is used is mainly reflected in the block section or route with two or more train occupation units. For such block section or route, the starting time of the occupation time of the second and subsequent train occupation units is no longer equal to that of the first train occupation unit (Eqs. 9.26, 9.27); instead, it is deduced from the continuity of the train operation process and all component items of the train occupation time. Since the preparation time, reaction time, clearing time and closing time remain unchanged in both cases, we combine the preparation time and reaction time with clearing time and closing time respectively, and then all component items of the train occupation time of two adjacent trains in the block section are shown in Fig. 10.18. For the block section or route with three train occupation units, we call the train occupation unit with no gap of occupation time between the adjacent trains as the bottleneck (indicated by the red dotted line in the figure). In Fig. 10.18, the train occupation unit 3 is the bottleneck. According to the continuity of the train operation process, it can be (2) (2) (2) known that t(2) con, 3 is related to tapp, 1, tocc, 1 and tocc, 2, and the relationship is shown in Eq. (10.13): ð2Þ

ð2Þ

ð2Þ

ð2Þ

tcon,3 ¼ tapp,1 + tocc,1 + tocc,2

(10.13)

In case the segmentation occupation mode is not used, the headway I is the sum of the clearing time, closing time, preparation time, reaction time,

FIG. 10.18

Comparison of train headways in two opening modes.

10.3 Calculation and adjustment of headway in station in segmentation release mode

389

running time and continuous time in the train occupation unit 3, as shown in Eq. (10.14): ð1Þ

ð1Þ

ð2Þ

ð2Þ

ð2Þ

ð2Þ

ð1Þ

ð1Þ

ð2Þ

ð2Þ

ð2Þ

ð2Þ

I ¼ tcel,3 + trel,3 + trou,3 + trea,3 + tcon,3 + tocc,3 ð2Þ

ð2Þ

¼ tcel,3 + trel,3 + trou,3 + trea,3 + tapp,1 + tocc,1 + tocc,2 + tocc,3 (10.14) In case the segmentation occupation mode is used, for the train occupation unit 3, the headway I3 is the sum of the clearing time, closing time, preparation time, reaction time, running time and braking time in the unit, as shown in Eq. (10.15): ð1Þ

ð1Þ

ð2Þ

ð2Þ

ð2Þ

ð2Þ

I 3 ¼ tcel,3 + trel,3 + trou,3 + trea,3 + tapp,3 + tocc,3

(10.15)

There is little difference in the preparation time (a in the figure), reaction time (b in the figure) and closing time (f in the figure) for trains with the same train control system passing through each train occupation unit. For trains of the same length and speed level, assuming that the train speed remains basically the same when they pass through the block section or route, it can be considered that the braking time (c in the figure) and the clearing time (e in the figure) in each train occupation unit are approximately equal. Therefore, when the train occupation unit 3 is the bottleneck, the effect ΔI3 of segmentation occupation mode on shortening the headway in station is shown in Eq. (10.16): ð2Þ

ð2Þ

ΔI 3 ¼ I  I 3  tocc,1 + tocc,2

(10.16)

In the same way, when the train occupation unit 1 or 2 is the bottleneck, the effect ΔI1 or ΔI2 can be deduced, as shown in Eqs. (10.17), (10.18) respectively: ð2Þ

ð2Þ

ð2Þ

ð2Þ

ΔI 1 ¼ I  I 1  tocc,2 + tocc,3 ΔI 2 ¼ I  I 2  tocc,1 + tocc,3

(10.17) (10.18)

The bottleneck is related to the structures of train occupation units included in the block section or route, and it is impossible to accurately predict which train occupation unit is the bottleneck in advance, so the effect ΔI of the segmentation occupation mode on shortening the headway in station can be expressed by the minimum of the above three values, as shown in Eq. (10.19). In the same way, the effect of the segmentation occupation mode on shortening the headway in station for the block section or route with two train occupation units or four or more train occupation units can be deduced, and thus, it’s not detailed here.

390

10. Development history of release modes

ΔI ¼ min

n




o ð2Þ ð2Þ ð2Þ ð2Þ ð2Þ ð2Þ tocc,1 + tocc,2 , tocc,2 + tocc,3 , tocc,1 + tocc,3

(10.19)

Shortening the headway at the bottleneck can effectively shorten the headway in the whole station, thus effectively improving the station carrying capacity.

References [1] Regulations of Railway Technical Operation (High-Speed Railway), China National Railway Group Limited, Beijing, 2014. [2] Technical Specification for Train Control Center, China National Railway Group Limited, Beijing, 2010. [3] RBC-CBI Interface Specification, China National Railway Group Limited, Beijing, 2010. [4] H. Zhang, J. Wang, X. Zhang, P. Xu, A method on improving the carrying capacity for CTCS-3 railway, J. Intell. Transp. Syst. 13 (3) (2021) 118–130, https://doi.org/10.1109/ MITS.2019.2962142. [5] J.F. Wang, et al., A novel space-time-speed method for increasing the passing capacity with safety guaranteed of railway station, J. Adv. Transp. 2017 (2017) 1–11, https:// doi.org/10.1155/2017/6381718. [6] P. Liu, Study on Capacity Calculation and Improvement Based on Refined Research of Headway in Stations for High Speed Railway, Beijing Jiaotong University, 2019.

C H A P T E R

11 Methods for improving the carrying capacity of high-speed railway and examples 11.1 Existing methods for improving station carrying capacity High-speed railway stations, as the junctions with large flows of trains and passengers, collect and distribute the passengers, and handle various train operations, including the arrival, departure, and transfer of trains. Therefore, the larger carrying capacity of high-speed railway stations is needed to improve the quality and capacity of passenger service of high-speed railway network. There are few studies specifically aiming at improving the station carrying capacity, and they mainly focus on improving the index of capacity utilization, reducing the route locking and release times, shortening the throat length, and improving the theoretical carrying capacity. Improving capacity utilization. On the premise of ensuring the service level, meeting the passenger needs, and ensuring the punctuality and reliability of train operation, John Armstrong and John Presto analyzed the relation between historic capacity utilization and congestion-related reactionary delay data, calculated the index of capacity utilization, to reduce the delay rate of trains and maximize the station carrying capacity [1]. Reducing route locking and release times. Wang Junfeng proposed a method for improving the station carrying capacity without increasing tracks or facilities. The existing fixed block districts are transformed into moving ones with shorter blocking time to improve the station carrying capacity and reduce the delay caused by the late trains. Then he took Shaoguan Station as a case for study, and it was found that the application of variable train-approaching locking section could improve the station carrying capacity by 0.6% to 6.3% (as shown in Fig. 11.1) [2].

Theory and Technology for Improving High-Speed Railway Transportation Capacity https://doi.org/10.1016/B978-0-323-99700-3.00008-6

391

Copyright © 2023 Elsevier Inc. All rights reserved.

392

FIG. 11.1

11. Methods for improving the carrying capacity

The improving percentage of passing.

Shortening the throat length. This method can reduce the interval between train operations, so as to improve the station carrying capacity. Aiming to maximize the number of passing trains, Li Xiaojuan established the model and algorithm to optimize the station carrying capacity based on the block optimization method, and studied the station route relationship model and the calculation method of operation interval. According to the case study, the proportion of trains of different operation types has a great impact on the station carrying capacity. Under the same conditions, the station carrying capacity can be increased by up to 30.8% after block optimization [3]. Improving theoretical carrying capacity. Burdett proposed the Railway Capacity Expansion Models (RCEMs), and employed the model to calculate the carrying capacity with a fixed budget given. He then studied and compared two methods, i.e., track duplications (RCEM-TRKDUP) and subdivisions (RCEM-SUBDIV) for their impacts on the carrying capacity. It is found that RCEM-SUBDIV results in lower cost and higher carrying capacity. RCEMs can replace manual operation in practical applications and have advantages in building a new railway network. They take the budget for the infrastructure into account but neglect the impact of the quantity and quality of the infrastructure on the carrying capacity [4]. None of the methods mentioned above can cover both the cases in sections and stations. In this book, the temporal-spatial network is constructed with 1 s as the time granularity in the temporal dimension, and the temporal-spatial is used to describe the activities of trains, such as their operation over the section from the originating station to the terminating station and intermediate stops.

393

11.2 Model and algorithm for improving the carrying capacity of high-speed railway

11.2 Model and algorithm for improving the carrying capacity of high-speed railway 11.2.1 Calculation model for district carrying capacity 11.2.1.1 Definitions and symbols 1. Sets Symbol

Definition

S G ¼ (N, E) N No Ns Nd Na E Eb Ee Ed Es L P Pl C

The set of stations, s  S Temporal-spatial network of high-speed railway The set of all nodes in the temporal-spatial network, n  N The set of sources, no  No The set of sinks, ns  Ns The set of departure nodes, nd  Nd The set of arrival nodes, na  Na The set of all directed arcs in the temporal-spatial network The set of beginning arcs, eb  Eb The set of ending arcs, ee  Ee The set of operation arcs in section, ed  Ed The set of dwelling arcs at station, es  Es The set of trains expected to be operated during peak hours, l  L The set of all possible temporal-spatial paths, p  P The set of possible temporal-spatial paths of operation for train l The set of temporal-spatial path pairs violating the headway in station, c  C A subset of P The set of active nodes during branching and bounding

 P A

2. Parameters Symbol

Definition

τ(n) nl,d s nl,a s p cfl tdwe p p0 UB d0 d d∗

The time corresponding to node n, n  N The departure node of train l at station s The arrival node of train l at station s Temporal-spatial path The penalty value for canceling the train l The total dwell time on p Virtual temporal-spatial path Upper bound during branching and bounding The root node in the branch and bound tree Nodes in the branch and bound tree Current active nodes in the branch and bound tree Continued

394

11. Methods for improving the carrying capacity

Symbol

Definition

M(d)

Linear programming model corresponding to a node d in the branch and bound tree The objective function value corresponding to M(d) Algorithm execution time limit Number of the temporal-spatial paths with pricing subproblem returning to restricted master problem

obj(M(d)) TX Nlj

3. Variables Symbol

Definition

xp

Whether the temporal-spatial path p is selected in the optimization result of transport capacity resources allocation. If yes, then xp ¼ 1; otherwise xp ¼ 0

11.2.1.2 Description of problems 1. Inputs The carrying capacity is calculated with train line planning, train service time, dwell time, and headway in station as input conditions. (1) The train line planning reflects the transportation demand, shows the operation districts, the set of stop stations, and operation frequency of trains of different speed levels, and constitutes the set L of trains expected to be operated. However, the train line planning only reflects the transportation demand. Limited by the resources such as track circuits and block sections, some trains in the set of trains expected to be operated may be canceled; (2) The train service time specifies the running time in section and additional time for starting and stopping of trains of different speed levels; (3) The dwell time includes the minimum dwell time and maximum dwell time of a train at each station; (4) Headway in station is an important technical parameter to determine the carrying capacity. For the calculation of the carrying capacity, the value of headway in station does not remain unchangeable, which is mainly reflected in the following aspects: a. Headway in station changes with the combination of operating speeds of adjacent trains over sections. The train operating speeds over sections on most high-speed railway lines are different. There are different combinations of operating speeds of adjacent trains over sections, under which the values of headway in station are

11.2 Model and algorithm for improving the carrying capacity of high-speed railway

395

different. For example, on a line (or section) subjected to the mixed operation of trains of two speed levels, there are four combinations of operating speeds of adjacent trains over sections: high-speed level-high-speed level, low-speed level-low-speed level, highspeed level-low-speed level, and low-speed level-high-speed level. b. Headway in station changes with the train operation state. Train operation state refers to the arrival, departure, or passing of the train at the station. There are nine types of combinations of operation states of adjacent trains, namely arrival-arrival, departure-departure, passing-passing, arrival-passing, passingarrival, departure-passing, passing-departure, arrival-departure, and departure-arrival. The values of headway in station are different under different combinations of operation states. c. Headway in station changes with the station. Due to the differences between different stations in terms of topology, route length, the diverging speed permitted on turnouts, allowable passing speed of the mainline, etc., there are also differences in horizontal and longitudinal sections of lines in its adjacent sections, speed limit areas and neutral zones, resulting in different values of headway in different stations. The operating speeds of adjacent trains over sections and train operation state are closely related to the train operation sequence. The train operation sequence is one of the elements to be optimized in the calculation of carrying capacity. With the change of train operation sequence, the values of headway in station need to be dynamically adjusted. According to the calculation method for headway in station proposed in Chapter 9, the values, accurate to 1 s, of headway in station can be obtained.

2. Outputs The purpose of carrying capacity is to organize as many trains for operation as possible, so it refers to the maximum number of trains that can operate. The carrying capacity is closely related to the transportation organization plan, and is affected by many factors such as the operation sequence of trains of different speed levels, speed difference, and stop schedule plan. The calculation model for district carrying capacity aims at organizing as many trains for operation as possible on the premise of ensuring operation safety. The model solution results clarify the maximum number of trains that can operate, train operation sequence, arrival, departure, or passing time of trains at stations along the line, etc.

396

11. Methods for improving the carrying capacity

To sum up, in order to calculate the district carrying capacity, the calculation model for district carrying capacity is established with train line planning, train service time, dwell time, and headway in station as inputs, and finally the district carrying capacity is obtained, as shown in Fig. 11.2. 3. Construction of the temporal-spatial network The temporal-spatial network is one of the important research methods in the field of transportation. With the help of classical theories of graph theory, the problems such as transport organization planning and optimization can be well solved. The temporal-spatial network abstracts the physical railway network into spatial nodes, and discretizes the time, and describes the activities of trains running in sections and dwelling at stations through directed arcs. In this book, the district carrying capacity is calculated based on the temporal-spatial network, for which the time is discretized to 1 s, the station is regarded as a whole to construct the temporal-spatial network, and the activities such as train operating in sections, arriving at, departing from or passing through stations are described. Let the temporal-spatial network G ¼ (N, E), where, N is the set of nodes, and E is the set of directed arcs. Let τ(n) be the time corresponding to the node n (n  N) to 1 s. (1) Nodes There are four categories of nodes, namely manual source (no), manual sink (ns), departure node (nd), and arrival node (na). Among them, no and ns are virtual nodes introduced for each train; nd indicates that the train departs from the station at τ(nd); na indicates that the train arrives at the station at τ(na). (2) Directed arcs There are four categories of directed arcs, namely beginning arc (eb), ending arc (ee), operation arc in section (ed), and dwelling arc at the station (es). eb connects no and nd; ee connects na and ns; ed connects nd of trains at a station and na of trains at the next adjacent station in the running direction, τ(na)  τ(nd) is the running time in the section. es connects na and nd of trains at the same station, and τ(nd)  τ(na) is the dwell time. (3) Temporal-spatial path The operation process of a train can be described by using the temporalspatial path, which is denoted as p, as shown in Fig. 11.3. The horizontal axis is the time axis and the vertical axis is the space axis. p starts from no and ends at ns, and passes nd and na of each station in the train operation section. p can be described as the sequential combination of different types of nodes and arcs, i.e., p ¼ {no, eb, nd, ed, na, es, …, ee, ns}.

FIG. 11.2

Capacity allocation of high-speed railway in busy sections during peak hours.

398

FIG. 11.3

11. Methods for improving the carrying capacity

A train path in directed time-space diagram.

(4) Set of temporal-spatial paths The train line planning is a known condition for calculating the carrying capacity, and L, the set of trains expected to be operated, is constructed according to the train line planning. According to the set of train operation districts and the set of stop stations of the train l (l  L), Pl, the possible set of temporal-spatial paths of each train can be obtained under the condition of meeting the constraints of running time in section, minimum dwell time, and maximum dwell time. Let the set of temporal-spatial paths of all trains be P. To sum up, calculating the carrying capacity is to obtain the maximum number of trains organized for operation by organizing as many trains in L, the set of trains as possible, giving priority to trains stopping at fewer stations, and finding the appropriate temporal-spatial paths for corresponding trains in P, the set of temporal-spatial paths in the temporalspatial network on the premise that there is no operation conflict. According to the optimization result, some trains in L may be canceled.

11.2.1.3 Objective function On the basis of the constructed temporal-spatial network, the decision variable (whose value might be 0 or 1) is introduced to represent whether to select a p (p  P) enabling further construction of the integer programming model [5,6] for carrying capacity calculation. Train line planning is made according to passenger flow demand. Some trains in L have to be canceled due to the constraint of transport capacity resources. Therefore, the model aims to minimize the penalty value for canceling the train to organize as many trains for operation as possible.

11.2 Model and algorithm for improving the carrying capacity of high-speed railway

399

High-speed railway trains stopping at stations will increase the additional time for starting and stopping and dwell time, thus prolonging the travel time and having a great impact on the carrying capacity. Therefore, priority can be given to trains stopping at fewer stations, the number of stops and the dwell time in the final optimization scheme can be reduced, and the model aims to minimize the dwell time. To sum up, the model aims at minimizing the penalty value for canceling the train and the dwell time, namely, 0 1 X XX X min cf l @1  xp A + tdwe xp (11.1) p pPl

lL

lL pPl

where cfl—the penalty value for canceling the train l; tdwe —the total dwell time on p, the temporal-spatial path; p xp—the decision variable, indicating whether to select p. If p is selected in the model solution results, then xp ¼ 1; otherwise xp ¼ 0. cfl is always greater than tdwe . Although adding a train stopping at the p station will increase the dwell time, the penalty for canceling the train is avoided. By giving the constraint cfl > tdwe , the objective of organizing p as many trains for operation as possible is met, that is, the objective function of the model is to maximize the number of trains organized for operation. 11.2.1.4 Constraints 1. Constraints on the uniqueness of temporal-spatial path There is a strong demand for passenger transportation, and some trains in L may be canceled. Therefore, the quantity of temporal-spatial path of each train l  L is up to one, namely X X xp  1, xp  1 (11.2) pPl

pPl

2. Constraints for the elimination of operation conflicts (1) Complying with headway in station The headway between adjacent trains at a station shall comply with the headway in station. In case the temporal-spatial paths of adjacent trains violate the constraint of headway in station, operation conflict will occur. According to the content of Chapter 9, the operation process of the train in the section and station is also considered for the calculation of headway in station, so there is no constraint of headway of tracking trains in the section in this model.

400

FIG. 11.4

11. Methods for improving the carrying capacity

Overtaking in section.

(2) Avoiding overtaking in the section For the section with long mileage, although the temporal-spatial paths of adjacent trains meet the constraint of headway in station, overtaking may occur in the section, as shown in Fig. 11.4. By checking the sequence of arrival, departure, or passing of adjacent trains at a station, it is possible to tell whether overtaking occurs in the section. The train departing from the station first should always arrive at the next station first, otherwise, the train operation sequence in the section changes, which means that overtaking occurs in the section, and there is definitely operation conflicts. To sum up, it is necessary to comply with the headway in station, so as to avoid overtaking in section. In case the temporal-spatial paths of adjacent trains violate the constraint of headway in station or overtaking occurs in a section, these two paths are called a pair of conflicting temporal-spatial paths (or conflict pair). At most one path in the conflict pair can be selected, namely X

xp  1, 8cC

(11.3)

pc

where C—the set of conflict pairs; c—one conflict pair, c  C. In the calculation of carrying capacity, the headway in station is closely related to the train operation sequence, which is one of the elements to be

11.2 Model and algorithm for improving the carrying capacity of high-speed railway

401

optimized. With the change of train operation sequence, the values of headway in station need to be adjusted accordingly. Therefore, the constraints for the elimination of operation conflicts are generated dynamically and continuously. (3) Constraints of decision variables The model decision variable xp is the value of 0-1, namely xp f0, 1g,8pPl ,8lL

(11.4)

11.2.2 Solution algorithm For the calculation of district carrying capacity, the time granularity is accurate to 1 s. With the expansion of the line study range, the temporalspatial path increases sharply. Therefore, the calculation model of carrying capacity is a large-scale integer programming model. Branch and bound algorithm (B&B algorithm), also known as implicit enumeration method, is a common method to solve integer programming. The efficiency of solving linear programming models corresponding to nodes in the branch and bound tree is very important. The calculation model of carrying capacity is constructed based on the temporal-spatial path, and the decision variable represents whether to select a temporalspatial path instead of a directed arc. Therefore, in this book, a B&B algorithm combined with column generation technology is designed, that is, the column generation technology is used, based on the branch and bound algorithm, to solve the linear programming of each node in the branch and bound tree. 11.2.2.1 Branch and bound algorithm The objective of optimizing the calculation model of carrying capacity is to minimize the penalty value for canceling train and the dwell time. Therefore, we only analyze the branching and bounding process of the integer programming model, whose objective function is corresponding to the minimization result. Firstly, the B&B algorithm solves the linear programming (LP) relaxation of the integer programming model for the root node in the branch and bound tree. If an integer feasible solution is obtained, it is the optimal solution of the integer programming model. Otherwise, the root node needs to be branched. The branching process is to select noninteger variables for branching according to the solution results to obtain two child nodes. The basic strategy of selecting variables for branching is to speed up the update of the upper bound and prune earlier in the branching process to reduce the

402

11. Methods for improving the carrying capacity

solving workload. In this book, the noninteger variable with the maximum fraction is selected as the variable for branching. The child nodes inherit the linear programming model of the parent node, and the constraint of variables 0 and 1 for branching respectively is added. Update the upper bound or prune according to the solutions of the linear programming models of child nodes. During branching and bounding, if the optimal solution of the linear programming model of a node is an integer feasible solution, and the optimal value of the objective function of the integer programming model is less than or equal to the objective function value of the linear programming model of the node, the objective function value corresponding to the current optimal integer feasible solution is defined as the upper bound. In the branch and bound tree, the objective function value of the linear programming of the parent node is greater than or equal to that of the child node. If the objective function value of the linear programming of a node is greater than the upper bound, it is impossible to obtain a better solution than the current optimal integer feasible solution even if further branching the node, so it is necessary to prune but not to further branch it. As the number of nodes in the branch and bound tree increases, it is necessary to select branching nodes by adopting an appropriate branching node selection strategy to improve the solving efficiency. Common branching node selection strategies include breadth-first strategy and depth-first strategy. (1) Breadth-first strategy As the branching process progresses, the target value of linear programming tends to increase; the breadth-first strategy is to select the node with the minimum objective function value of linear programming in the set of active nodes for branching. (2) Depth-first strategy The number of layers of the branch and bound tree—the number of variables branched—is defined as the depth of the node. The depth-first strategy is to select the node with the maximum depth for branching. In this book, after testing, the breadth-first strategy is used to select the branching nodes. The depth-first strategy allows to quickly find the integer feasible solution, but the quality of the solution is not high. However, it is slow to find an integer feasible solution by using the breadth-first strategy, but the quality of the solution is high. 11.2.2.2 Solution of linear programming model of node based on column generation technology Column generation technology has been widely applied in solving large-scale linear programming models [7–14] and has been successfully applied in solving path-based multicommodity flow models. When it is

11.2 Model and algorithm for improving the carrying capacity of high-speed railway

TABLE 11.1

403

Pricing subproblem of different linear programming models.

Linear programming model

Pricing subproblem

Bin packing problem

Knapsack problem

Crew pairing problem

Shortest path problem with resource constraints

Cutting stock problem

Knapsack problem

Job shop problem

Single-machine scheduling problem with time window

Multicommodity network flow problem

Shortest path problem

Vehicle routing problem

Traveling salesman problem

applied, only part of the solution space is selected to solve the restricted master problem, the pricing subproblem is constructed in combination with the optimality test conditions, and the solution space of the restricted master problem is updated until the algorithm termination conditions are met. The pricing subproblem is constructed according to the optimality test conditions of the linear programming model, and there are differences among pricing subproblems of different linear programming models, as shown in Table 11.1. Effectively solving pricing subproblems is the key of column generation technology, affecting the quality of new variables introduced in the solution space of the restricted master problem. The calculation model of carrying capacity proposed in this book is accurate to 1 s. It is difficult to enumerate all the elements in P, and the solution space is huge. When the branch and bound algorithm is used to solve a model, the scale of the linear programming model corresponding to the node is large, restricting its solving efficiency. In this book, considering that the calculation model of carrying capacity is based on the characteristics of the temporal-spatial path, the column generation technology is used to solve the linear programming model of the node in the branch and bound tree. Some scholars call such an algorithm branch and price algorithm [15–21]. For the linear programming model of branching node, by using the column generation technology, the initial feasible solution is firstly constructed, which is used as the initial solution space of the restricted master problem; secondly, the value of the dual variable is obtained by solving the restricted master problem; thirdly, the pricing subproblem is solved and the optimality of the solution is judged according to the value of the dual variable. If the optimality conditions are met, the optimal result is obtained, and the solving process is terminated. Otherwise, a new temporal-spatial path is generated and introduced into the solution space of the restricted master problem according to the solution of the pricing subproblem, and the restricted master problem is re-solved. In the process

404

11. Methods for improving the carrying capacity

of solving the calculation model of carrying capability, the concrete construction methods of an initial feasible solution, restricted master problem, and pricing subproblem are as follows. (1) Initial feasible solution (virtual temporal-spatial path) Column generation always keeps the solution feasible in the solving process, and the initial feasible solution needs to be constructed before solving the model. For each train l (l  L), a virtual temporal-spatial path (p0 ) is constructed and written into the set Pl. Assuming that there is no operation conflict between p0 and other paths p(p  Pl,p 6¼ p0 ), the virtual temporal-spatial paths of all trains are the feasible solutions of the model M(d∗) and constitute the initial values of the set P. (2) Restricted master problem Since each train l (l  L) has a temporal-spatial path, the number of the temporal-spatial paths must be one in the solutions of the calculation model of carrying capacity. Therefore, the constraint Eq. (11.2) is corrected to Eq. (11.5). If the p0 of the train l is selected in the model solution, the train l is canceled. X xp ¼ 1, 8lL (11.5) pPl

Let

the total dwell time of p0 , be cfl for canceling the train l, i.e., the objective function Eq. (11.1) is corrected to Eq. (11.6). XX min tdwe (11.6) p xp

tdwe p0 ,

tdwe ¼ cfl, p0

lL pPl

To sum up, let Pl be a subset of the set of temporal-spatial paths of the train, i.e., Pl  Pl , the restricted master problem is: XX min tdwe (11.7) p xp lL pPl

X

xp ¼ 1, 8lL

(11.8)

xp  1, 8cC

(11.9)

pPl

X pc

xp  0, 8pPl , 8lL

(11.10)

(3) Pricing subproblem The pricing subproblem is used to introduce new temporal-spatial paths and update P constantly. Let π l and π c be dual variables of constraint

11.2 Model and algorithm for improving the carrying capacity of high-speed railway

405

Eqs. (11.8) and (11.9) respectively, where, π l is a free variable, and π c 0. The number of inspection σ p for the temporal-spatial path p is calculated by Eq. (11.11). XX XX σ p ¼ tdwe  πl + πc (11.11) p lL pPl

cC pc

If σ p 0 for all p’s in the set P, the optimal solution of the linear programming model is obtained. Otherwise, the nonbasic variable xp with negative number of inspection is introduced into the basic variable. (Optimality test condition.) Accordingly, the pricing subproblem is constructed as popt, the “shortest” temporal-spatial path with Eq. (11.12) as the objective function opt in the temporal-spatial network. If Zp < 0, then popt is introduced into the subset P. The operation conflict is checked according to the headway in station and the fact that whether overtaking occurs in a section, C is dynamically updated, and the restricted master problem is resolved. min Zp ¼ tdwe  p

XX lL pP’ l

πl +

XX

πc

(11.12)

cC pc

11.2.2.3 Process of branch and bound algorithm Let the set of active nodes be A, the upper bound be UB, the node in the branch and bound tree be d (where the root node is d0), the linear programming model corresponding to the node d be M(d), the objective function value corresponding to the model be obj(M(d)), and the algorithm execution time limit be TX. The steps of the branch and bound algorithm combined with column generation technology are as follows: Step 1: Initialization. Let A ¼ {d0}, UB ¼ + ∞, initialize the linear programming model M(d0) of the root node d0 to the linear programming relaxation of the calculation model of carrying capacity. Step 2: Determine whether the algorithm termination conditions are met. Step 2.1: If A ¼ ∅, then the algorithm is terminated; otherwise, move to Step 2.2. Step 2.2: If the algorithm execution time does not exceed TX, select the branching node d∗ from the set A of active nodes as the currently active node by adopting the breadth-first strategy, and move to Step 3; if the algorithm execution time exceeds TX, delete several trains in the set of trains in turn, update the set L of trains, and move to Step 1. Step 3: Solve the linear programming model M(d∗) of the currently active node d∗ by using the column generation technology to obtain the objective function value obj(M(d∗)).

406

11. Methods for improving the carrying capacity

Step 3.1: Construct the initial feasible solution. Construct a virtual temporal-spatial path p0 for each train l (l  L), and the virtual temporalspatial paths of all trains are the initial feasible solutions of the model M(d∗) and constitute the initial values of the set P. Step 3.2: Limit the set of temporal-spatial paths to P (P  P), and solve the restricted master problem, as shown in Eqs. (11.7) to (11.10). In addition, if the branching node d∗ limits the value of some decision variables to 0 or 1, the constraint equation Eq. (11.10) needs to be corrected. Step 3.3: Solve the pricing subproblem and update the subset P. Solve the pricing subproblem with Eq. (11.12) as the objective function. opt If Zp < 0, then introduce the “shortest” temporal-spatial path popt into the subset P, and update C. With the idea of edge deletion method [22], randomly delete the operation arc in section or dwelling arc at a station in the temporal-spatial path popt, and re-solve the pricing subproblem to obtain the “secondary shortest” temporal-spatial path popt, which is introduced into the subset P. Repeat until the number of temporal-spatial paths with pricing subproblem returning to restricted master problem reaches Nlj. After the pricing subproblem is solved, re-solve the restricted master problem, and move to Step 3.2. If no temporal-spatial path can be found to meet the pricing subprobopt lem Zp < 0, the model is solved, and then move to Step 4. Step 4: Delete the node d∗ from the set A of active nodes, and branch or prune according to the relationship of size between obj(M(d∗)) and UB. If obj(M(d∗)) < UB, and the values of the decision variables of model M(d∗) are all integers, then update the upper bound UB ¼ obj(M(d∗)) and move to Step 2. (Update the upper bound.) If obj(M(d∗)) UB, then the branching node d∗ is pruned and no child nodes are generated. (Prune.) If obj(M(d∗)) < UB, and the values of the decision variables of model M(d∗) are not all integers, calculate the deviation value ηp between the noninteger variable xp and 0 or 1 according to Eq. (11.13), and select the variable x∗p with the maximum deviation value as the variable for branching, and this decision variable is the noninteger decision variable with the maximum fraction. Let x∗p ¼ 0, x∗p ¼ 1, respectively construct the child nodes of the node d∗, and write the child nodes into the set A of active nodes, and then move to Step 2. (Branch.)       (11.13) ηp ¼ min xp  xp , xp  xp where ηp—the deviation between noninteger variable xp and integers;

11.2 Model and algorithm for improving the carrying capacity of high-speed railway

FIG. 11.5

407

Flowchart of branch and bound algorithm.

bxpc—the maximum integer less than or equal to xp; dxpe—the minimum integer greater than or equal to xp. To sum up, the process of the branch and bound algorithm combined with column generation technology is shown in Fig. 11.5. In this book, C# is used to program the branch and bound algorithm. For the linear programming model of the branching node, based on the

408

11. Methods for improving the carrying capacity

principle of column generation, the algorithm of ILOG CPLEX is called through the component library to solve the restricted master problem and the pricing subproblem, and the integration of column generation technology and branch and bound algorithm is realized. For specific programming syntax, refer to IBM ILOG CPLEX V12.3 User’s Manual for CPLEX.

11.3 Case study of application Beijing-Shanghai high-speed railway, officially put into service on June 30, 2011, is a key channel connecting the more developed areas in eastern China with a design maximum speed of 380 km/h, 24 stations in total, and a total length of 1318 km, in which Xuzhou East-Bengbu South District is the district in most short of carrying capacity. This part takes the district mentioned above as an example, calculates its district carrying capacity, and evaluates how segmentation release of block sections and routes influences the headway in station and the carrying capacity, so as to provide support for calculating and strengthening the carrying capacity.

11.3.1 Calculation of district carrying capacity As for the calculation method of carrying capacity proposed in this book, the time granularity is 1 s, and it is considered that the headway in station changes along with the speed of adjacent trains in sections and their operation state in stations. Shown is the calculated carrying capacity in the down direction as an example. 11.3.1.1 Calculation parameters and operation scenes (1) Train line planning After analyzing the current train operation situation in Xuzhou EastBengbu South District, the period [9:00, 11:30] is taken for study. The train line planning during this period is shown in Fig. 11.6, based on which is built the set L of a total of 40 trains expected to be scheduled. To provide more balanced transportation services and avoid excessive concentration of trains of the same type, the operation time windows for trains expected to be scheduled are further restricted, as shown in Table 11.2. (2) Train service time According to the calculation results of the respective operation curve of stopping and passing trains, obtained is the running time in sections and

409

11.3 Case study of application

FIG. 11.6

Train service plan during peak hours.

the additional time for starting and stopping in the Xuzhou East-Bengbu South Section when the train operate at 300 km/h, as shown in Table 11.3. (3) Dwell time The min and max dwell times at Suzhou East Station are 1 min and 9 min, respectively. (4) Headway in station under different scenes Two scenes are set to analyze how headway in station influences the calculated carrying capacity, and the specific values of headway in such scenes are shown in Table 11.4. In Scene 1, headway in station is accurate to 1 s and varies with the operation state of adjacent trains and the station. A specific value of headway is calculated in Chapter 9, which is the maximum headway of adjacent trains in the same direction in a station. In Scene 2, headway in station is accurate to 1 min and varies only with the operation state of adjacent trains. Refer to the Train Headway Standard for specific values. TABLE 11.2

Time windows for trains expected to be scheduled.

S/N

Operation time window

Train line 1 (train(s))

Train line 2 (train(s))

Train line 3 (train(s))

Train line 4 (train(s))

Total (train (s))

1

[9:00,10:00]

4

4

–

–

8

2

[9:30,10:30]

4

1

1

2

8

3

[10:00,11:00]

5

1

1

1

8

4

[10:30,11:30]

4

2

2

–

8

5

[11:00,12:00]

5

1

1

1

8

22

9

5

4

40

Total

410

11. Methods for improving the carrying capacity

TABLE 11.3 Running time in track sections and additional time. Running time in sections (s)

Additional time for starting (s)

Additional time for stopping (s)

Xuzhou East-Suzhou East

780

78

57

Xuzhou East-Bengbu South

1028

84

56

Section

(5) Operating environment and algorithm parameters The B&B algorithm is programmed in C# with Visual Studio 2010, and then CPLEX 12.3 is used to solve restricted master problems and subproblems. The computer CPU is Intel Core2 i7 2.80 GHz and the memory is 4 G. It is determined by trial and error that the algorithm execution time TX is 120 min and the penalty value for canceling trains is 600 s.

11.3.1.2 Results of carrying capacity calculation (1) Algorithm analysis In Scene 1, the objective function varies in value when solved using the branch and bound algorithm proposed in this book, as shown in Fig. 11.7. The total operation time is 1169.2 min, and the optimal solution (5400 s) is obtained after 390.7 min, corresponding to 32 trains. Thus it is evident that the carrying capacity can be calculated effectively with the solution algorithm proposed in this book. (2) Comparison and analysis of calculated carrying capacities The calculated carrying capacities in both scenes are shown in Table 11.5. In Scene 1, the objective function has an optimal value of 5400 s when the carrying capacity is 32 trains and the total dwell time is 600 s, as shown in Fig. 11.8. In Scene 2, the objective function has an optimal value of 6960 s when the carrying capacity is 29 trains and the total dwell time is 360 s, as shown in Fig. 11.9. According to the comparison above, it is found that there will be three more trains operating in Scene 1 than in Scene 2. Hence for the calculation of carrying capacity, it is necessary to have headway in station accurate to 1 s and take into account that the headway changes along with the speed of adjacent trains in sections and their operation state in stations.

TABLE 11.4 Headways under different scenes (s). Arrivalarrival

Departuredeparture

Passingpassing

Departurearrival

Arrivaldeparture

Arrivalpassing

Passingarrival

Departurepassing

Passingdeparture

Xuzhou East

189

185

178

0

0

135

262

326

93

Suzhou East

184

176

160

0

0

131

242

316

76

Bengbu South

184

196

179

0

0

142

282

338

86

Xuzhou East

240

240

180

240

180

240

240

240

120

Scene

Station

Scene 1

Scene 2

412

11. Methods for improving the carrying capacity

FIG. 11.7

Change of objective value in the solving process.

TABLE 11.5

Capacities in peak hours under different scenes.

Train line number

Scene 1 (train count)

Scene 2 (train count)

1

18

18

2

6

3

3

4

5

4

4

3

Total

32

29

FIG. 11.8

Capacity allocation results of Scene 1.

11.3 Case study of application

FIG. 11.9

413

Capacity allocation results of Scene 2.

11.3.2 Analysis on effect of segmentation release mode in improving carrying capacity of high-speed railways 11.3.2.1 Effect in shortening headway in station Taking Xuzhou East Station as an example, the changes in its headway and bottleneck are analyzed with the segmentation release mode used for block sections and routes. The segmentation release of block sections does not mean its application to all block sections, and instead, the mode is applied only if two or more track circuits are included in the block section adjacent to the station. In the up direction, for example, the block section adjacent to Suzhou East Station in Suzhou East-Xuzhou East District has only one track circuit, and thus it is not open in segments. Refer to Table 11.6 for the number of operation conflict areas in each track section before and after opening the block section in segments. Before segmentation release mode is applied, the operation conflict areas are recognized in terms of block section. After segmentation release mode is applied, the operation conflict areas are recognized in terms of track circuit in the concerned block section. (1) Calculation results of headway in Xuzhou East Station after segmentation release Table 11.7 shows the calculated headway and bottleneck in Xuzhou East Station after segmentation release of block sections and routes when the operating speeds of adjacent trains are both 300 km/h.

414

11. Methods for improving the carrying capacity

TABLE 11.6 Number of block sections for each track section. Number of operation conflict areas Before application of segmentation release

After application of segmentation release

Section

Up

Down

Up

Down

Dingyuan-Bengbu South

28

28

30

29

Bengbu South-Suzhou East

46

46

47

47

Suzhou East-Xuzhou East

35

36

36

37

Xuzhou East-Zaozhuang West

34

34

36

35

(2) Analysis of calculation results Table 11.8 shows the changes in the number of route combinations corresponding to different types of headway in station after the segmentation release mode is applied for block sections and routes, as well as the maximum, minimum, and mean of the shortened headway in station. a. The effect in shortening headway in station differs from type to type. The effect is most obvious for the headway between a passing train and a departure train in opposite directions whose route types are combined into II and III (this headway type is numbered 18), and its mean reduction reaches 66 s. Many trains stop in large stations. The headway of a pair of arrival trains is reduced by about 17 s on average, and it is reduced in all route combinations. The headway of a pair of departure trains is reduced by about 19 s on average. b. The effect in shortening different types of headway in station is closely related to the bottleneck. After segmentation release mode is used, some types of headway in station (types 16, 20, 21) remain, and do the bottlenecks related. For example, when the routes of adjacent trains are Route 17 (down departure route) and Route 73 (up through route) respectively, the bottleneck is at {2DG, 4DG}, the first minimum block section in station that the following passing train passes through in the station. The corresponding headway in station remains even though the starting time of the train occupation time differs among different minimum block sections in the station on the through route. After the segmentation release mode is used, most headways in station are shortened, and the bottlenecks related changes. For example, when the routes of adjacent trains are Route 58 (down receiving route) and Route 60 (down receiving route), the bottleneck is at the 34th block section

TABLE 11.7 Headways and bottlenecks after partition of block sections and train routes for Xuzhou East station. Route combination Operation state

Route combination

Running direction

Number of combinations

Maximum (s)

Minimum (s)

Average (s)

1

Arrivalarrival

I+I

Same direction

188

175

149

162

2

Arrivalarrival

II + II

Same direction

116

174

150

161

3

Arrivalarrival

I + II

Same direction

308

175

149

161

4

Departuredeparture

I+I

Same direction

188

176

150

163

5

Departuredeparture

II + II

Same direction

116

174

152

164

6

Departuredeparture

I + II

Same direction

308

175

151

164

7

Passingpassing

III + III

Same direction

2

145

145

145

Block section 17 in the up direction from Xuzhou East to Zaozhuang West, block section 27 in the down direction from Zaozhuang West to Xuzhou East

8

Arrivalpassing

I + III

Same direction

21

115

45

66

IG2,{1-9DG,1517DG},47DG,IIG1,

S/N

Bottleneck Block section 33 in the up direction from Zaozhuang West to Xuzhou East, block section 34 in the down direction from Suzhou East to Xuzhou East

Block section 33 in the up direction from Xuzhou East to Zaozhuang West, block section 35 in the down direction from Xuzhou East to Suzhou East

Continued

TABLE 11.7 Headways and bottlenecks after partition of block sections and train routes for Xuzhou East station—cont’d Route combination S/N

Operation state

Route combination

Running direction

Number of combinations

Maximum (s)

Minimum (s)

Average (s)

Bottleneck {26DG,28-42DG},{612DG,8-10DG}

9

Arrivalpassing

II + III

Same direction

15

68

39

52

47DG,{6-12DG,14-22DG}

10

Arrivalpassing

II + III

Opposite direction

12

122

35

56

IIG2,{21DG,23-39DG},{513DG,7DG},IG1

11

Passingarrival

I + III

Same direction

21

261

244

250

12

Passingarrival

II + III

Same direction

15

261

245

250

Block section 1 in the up direction from Suzhou East to Xuzhou East, block section 27 in the down direction from Zaozhuang West to Xuzhou East

13

Passingarrival

II + III

Opposite direction

12

156

105

141

3-51DG,IG2

14

Departurepassing

I + III

Same direction

21

325

307

320

15

Departurepassing

II + III

Same direction

15

325

308

321

Block section 34-2 in the up direction from Xuzhou East to Zaozhuang West, block section 36-2 in the down direction from Xuzhou East to Suzhou East

16

Departurepassing

II + III

Opposite direction

11

221

211

219

{2DG,4DG}

17

Passingdeparture

I + III

Same direction

21

70

20

33

21DG,5-13DG,{1422DG,16DG},2DG

18

Passingdeparture

II + III

Same direction

15

70

9

20

5-13DG, block section 1 in the down direction from Xuzhou East to Suzhou East

19

Passingdeparture

II + III

Opposite direction

11

49

7

15

26DG,6-12DG

20

Arrivaldeparture

II + II

Opposite direction

–

–

–

–

–

21

Arrivaldeparture

I + II

Opposite direction

64

5

4

5

{19-31DG,33DG},{2339DG,41DG},43DG,45DG, {24-38DG,40DG},{2842DG,44DG},46DG,48DG

22

Departurearrival

II + II

Opposite direction

88

286

246

266

3-51DG,{2DG,4DG}

23

Departurearrival

I + II

Opposite direction

268

286

174

258

3-51DG,{15-17DG,1931DG},{19-31DG,33DG}, {2DG,4DG},{14-22DG,2438DG},{24-38DG,40DG}

TABLE 11.8 Shortening effect of headway after partition of block sections and train routes for Xuzhou East station. Type of headway

1

2

3

4

5

6

7

8

9

10

11

12

Number of route combinations reduced

188

116

308

104

12

88

2

15

4

12

10

11

Maximum shortened headway (s)

19

19

19

22

21

22

33

22

2

27

1

1

Minimum shortened headway (s)

13

13

13

9

10

9

26

2

2

13

1

1

Mean shortened headway (s)

16

18

17

20

18

19

30

7

2

24

1

1

No.

13

14

15

16

17

18

19

20

21

22

23

The number of route combinations reduced

12

10

11

0

21

15

10

0

0

44

147

Maximum shortened headway (s)

57

1

1

0

63

74

38

0

0

37

73

Minimum shortened headway (s)

37

1

1

0

13

23

30

0

0

37

37

Mean shortened headway (s)

39

1

1

0

55

66

34

0

0

37

41

11.4 Outlook

419

(i.e., the block section adjacent to Xuzhou East Station) in the down direction from Zaozhuang West to Xuzhou East before segmentation release mode is used. After segmentation release mode is used, the headway is reduced by 19 s, the block section is divided into two smaller and independent block section, and the bottleneck changes to the 33rd block section in the down direction from Zaozhuang West to Xuzhou East. 11.3.2.2 Effect in improving the carrying capacity According to calculation results of headway in station, after segmentation release mode is applied to the block sections and routes as stated in Section 11.3.2.1, the maximums of headway in the same direction are taken as the input conditions for calculating the carrying capacity, as shown in Table 11.9. Table 11.10 shows the results of carrying capacity provided with the same operating environment and algorithm parameters (see Section 11.3.1.1). The objective function has an optimal value of 3060 s when the carrying capacity is 36 trains and the total dwell time is 11 min, as shown in Fig. 11.10. Compared with Scene 1 (see Section 11.3.1.2), four more trains can be scheduled after segmentation release mode is applied to the block sections and routes, which means that this application will result in shorter headway in station and further greater carrying capacity.

11.4 Outlook At present, the carrying capacity is still calculated by the method for existing railway passenger stations, and the research on improving the station carrying capacity mainly focuses on improving the theoretical carrying capacity, reducing route locking and release times, and shortening the throat length. In this book, the impact of districts on the station carrying capacity is taken into consideration, and precise headway in station and segmentation release mode is employed to improve the carrying capacity. In future research, attention might be paid on collaborative optimization of multiple stations in operation organization and virtual marshaling, to further improve the station carrying capacity.

11.4.1 Collaborative optimization of multiple stations in operation organization According to the solution proposed in this book, the first step is to clarify the quantitative relationship between the organization mode of train transportation, the technical operations and the station carrying capacity

TABLE 11.9 Headways after partition of block sections and train routes. Arrivalarrival

Departuredeparture

Passingpassing

Departurearrival

Arrivaldeparture

Arrivalpassing

Passingarrival

Departurepassing

Passingdeparture

Xuzhou East

175

176

145

0

0

115

261

325

70

Suzhou East

166

172

142

0

0

116

242

310

76

Bengbu South

184

185

145

0

0

120

277

341

70

Station

11.4 Outlook

421

TABLE 11.10 Capacities in peak hours after partition of block sections and train routes. Train line number

Scene 3

1

20

2

7

3

5

4

4

Total

36

according to the temporal-spatial characteristics of train tracking operation on high-speed railway after segmentation release mode is used for track circuits and based on the proposed precise calculation method of headways under different combinations of speed over sections and different route combinations; and the second step is to optimize the collaboration of the operations organization plan of different trains at different stations combining both the macro and micro perspectives, to obtain the organization plan for technical operations at multiple stations on a line with precise headways in station, in which the goal is to refine the technical operation organization of trains, and the focus is on the selection of throat routes, the utilization of tracks, and the handling of operations for entering and leaving the depot. This lays the foundation for the next

FIG. 11.10

Capacity allocation results after partition of block sections and train routes.

422

11. Methods for improving the carrying capacity

move, namely optimizing the utilization of station carrying capacity based on refined technical operation organization of stations. From the micro perspective, where an individual station is taken as the object of study, the operation process of station is reorganized based on segmentation release mode, to improve the operation efficiency of station and minimize train delays, and then the mechanism how the throat route, track utilization, train operation mode and other factors influence the utilization of track resources is considered, to obtain the optimal process for train operations at stations. From the macro perspective, where the whole line is taken as the object of study, an optimization model for collaborating the train operation organizations of multiple stations is established considering that the headway in station changes along with the speed of adjacent trains in sections and their operation state at stations, to integrate the train tracking process in sections and stations by reducing operations at large stations and increasing operations at small stations, so as to realize reasonable allocation of resources in sections and stations and further to optimize the capacity utilization effect.

11.4.2 Virtual marshaling Virtual marshaling is a technical means for realizing real-time, rapid recoupling, or uncoupling of trains of the same or different models during operation, which replaces mechanical coupling with direct radio communication between trains. After the virtual marshaling technology is applied to the urban rail transit system, trains of different numbers on the same line can be coupled or uncoupled according to the operation requirements either in station when they stand still or in sections when they are traveling. This real-time dynamic marshaling mode not only shortens headways and improves the transportation capacity of the line, but also brings about innovation of the operation organization mode toward “smaller formation and higher density,” and provides new options for transportation organization optimization. This is mainly reflected in but not limited to the following three aspects: (1) Using virtual marshaling for time-interval based dynamic marshaling, to eliminate the contradiction between the constant train capacity that is and the changing passenger flow volume with time. Virtual marshaling is featured by short operation time in remarshaling and independence from sites. On this basis, a novel transportation organization mode of time-interval based flexible marshaling and district based dynamic coupling and uncoupling can be achieved through real-time online coupling and uncoupling, and the limitation of marshaling due to platform length can be broken by breaking up the formation of a train before it enters the station;

References

423

(2) Using virtual marshaling for operating trains at different speeds and with different route lengths in a more flexible and diverse way, to eliminate the contradiction between simple train line planning on a line and complex requirements for the passenger flow process and time. Virtual marshaling is featured by short headways. On this basis, new transportation organization strategies can be implemented, such as faster trains overtake preceding slower trains, slower trains give way to following faster trains, and faster trains and slower trains can exchange the cars in the drop-and-pull mode; furthermore, diversified stop schedule plans and routing schemes based on the passenger flow demand can be realized, to can meet a variety of travel demands of different passengers; (3) Using virtual marshaling for operating multiple cross-line trains according to real-time passenger flow conditions, to eliminate the contradiction between the fixed structure of railway network and versatile passenger flow directions. Virtual marshaling enables meeting the technical requirements for rapid coupling and uncoupling of trains in stations and sections, and cutting the times for tracking, turning back, and line crossing operations.

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[13] D. Huisman, A column generation approach for the rail crew re-scheduling problem, Eur. J. Oper. Res. 180 (1) (2007) 163–173. [14] V. Cacchiani, A. Caprara, P. Toth, A column generation approach to train timetabling on a corridor, 4OR 6 (2) (2008) 125–142. [15] J. Desrosiers, F. Soumis, M. Desrochers, Routing with time windows by column generation, Networks 14 (4) (2010) 545–565. [16] C. Barnhart, E.L. Johnson, G.L. Nemhauser, et al., Branch-and-Price: column generation for solving huge integer programs, Oper. Res. 46 (3) (1998) 316–329. [17] C. Barnhart, C.A. Hane, P.H. Vance, Using branch-and-price-and-cut to solve origindestination integer multicommodity flow problems, Oper. Res. 48 (2) (2000) 318–326. [18] R. Fukasawa, H. Longo, J. Lysgaard, et al., Robust branch-and-cut-and-price for the capacitated vehicle routing problem, Math. Program. 106 (3) (2006) 491–511. [19] M. Savelsberg, Branch and Price: Integer Programming with Column Generation BP, 2009, pp. 328–331. [20] V. Cacchiani, Models and algorithms for combinatorial optimization problems arising in railway applications, 4OR 7 (1) (2009) 109–112. [21] B. He, R. Song, S. He, et al., High-speed rail train timetabling problem: a time-space network based method with an improved branch-and-price algorithm, Math. Probl. Eng. 2014 (1) (2014) 1–15. [22] V. Cacchiani, L. Galli, P. Toth, A tutorial on non-periodic train timetabling and platforming problems, EURO J. Transp. Logist. 4 (3) (2015) 285–320.

Index Note: Page numbers followed by f indicate figures and t indicate tables.

A

Adaptive dynamic coding rules and algorithms for track circuit, 153–157 safety and capacity, 157–159, 158f, 160t, 160f for track circuit in CTCS -3, 147–159 ATO. See Automatic train operation (ATO) ATP protection curve algorithm, of CTCS-3I train control system, 199–206 European standard method, calculation model of, 201–203, 202f genetic algorithm, 204–206 optimization model, 203–204 simulation algorithm principle, 207 simulation calculation of train running resistance, 208–209 speed protection model, 209–212 Automatic block, 361 double track, 26 efficiency, 29–30 moving block, 28 single track, 27 static tracking, 28 Automatic train operation (ATO) comparison of train control flow, 101f CTCS2+ATO system, 102–104 development status and research, 105–106 high-speed railway structure, 104f system architecture and fundamentals, 101–102 Automatic train protection (ATP), 15, 62–63, 230–231 Autonomous handling route, 232 Auto-passing phase separations, 259 Average minimum train interval method, 275

B

Backtrack protection, 195 Balise transmission module (BTM), 194 Block section and train route

blocking mode for high-speed railways in China, 362–363 development history of release modes, 359–362 movement authority of train control system, 364–368 optimization methods, 368–369 release rules in China, 363–364 station route setting, 363–364 train operation organization of sections in China, 363 Block section recombination flag (BSR), 154–156 BNSF centralized dispatch command, 49 Braking distance, 164, 164t, 168, 178 Braking mode driver priority control, 31 equipment priority control, 31 Braking process, 201

C

Calculation method arrival-departure headway, 287–288 arrival headway, 285–287 crossing headway, 287 departure-arrival headway, 287–288 opposite passing headway, 288 Carrying capacity of high-speed railways Beijing-Shanghai, 159 calculation methods, 268–276 characteristics, 266–268 collaborative optimization, 419–422 definition, 263–266 district carrying capacity, 408–412 existing methods, 391–392 facilities and equipment, 276–279 horizontal and longitudinal sections, 281 improving carrying capacity, 419 model and algorithm, 393–408 passenger service rules, 282 segmentation release mode, 413–419 shortening headway in station, 413–419

425

426

Index

Carrying capacity of high-speed railways (Continued) station operation organization, 281 traction districts of lines, 281 train operation organization, 279–280 virtual marshaling, 422–423 CBTC system. See Communication-based train control (CBTC) system China Railway dispatching information system CTC1.0 system, 98–99 high-speed railway dispatching technology, development of, 98, 98f TMIS and DMIS, 98 China train operation control system (CTCS), 80 Chinese Train Control System Level 3 (CTCS-3) automatic block system, 152–153 existing track circuit coding principle and shortcoming, 149–153, 152f ZPW-2000A track circuit structure and code sequence, 148–149, 149f, 150t, 151f Chromosome coding, 204 Coefficient removal method, 275 Cognitive reliability and error analysis method (CREAM), 69–71 Combined fast and slow service scheme, 176–177, 176f Communication-based train control (CBTC) system control and structure, 80–82 vehicle-to-vehicle communication, 85–86 vehicular communication technology, 82–83 Comprehensive transportation stage, 3 Constraints initialization, 324 train occupation time, 324 Cooperative control characteristics, 236–238 classical mathematical model, 234 combined with dispatching, 247–248 down-top models, 236 real-time interval adjustment, 243–247 research on train cooperative control, 236, 237f top-down models, 234 train operation mode, 238–239 trains to reduce delay time, 240–243 UTRAS system, 235–236

Cooperative Shortening Movement Authority (CSMA), 220–222, 221f CTCS-3. See Chinese Train Control System Level 3 (CTCS-3) CTCS-3+ATO train control system, 24f CTCS-3I train control system architecture and function, 192–197 ATP protection curve algorithm, 199–206, 200f ground equipment, 192–193 moving block, 189–192, 196–197, 197t on-board equipment, 193–194 optimization algorithm of movement authority, 212–222 optimization of overspeed protection curve based on train braking, 206–212 software execution process, 197–199 technical characteristics, 194–196 CTCS-3 track circuit adaptive dynamic coding algorithms, 154–156, 154–155f capacity, 158–159, 160f, 160t handling boundary values, 156–157 principle, 153, 154f safety, 157, 158f CTCS-3 train control system distance-to-go speed mode control, 376f, 378f movement authority, 365, 367 Curve calculation synchronization technology, 195–196 Curvilinear hierarchical speed control EO-PTC, 38 ERTMS, 38–41 primary braking mode, 34–38

D

Data recording, 196 Definitions of symbols parameters, 321–322t sets, 321t variables, 322t Departure tracking interval, 126 Dispatching command system C-DAS CATO, 53f, 54 centralized traffic control system (CTC), 48–50 existing dispatching and intelligent dispatching, 48f railway control system (RCS), 47 STEG, 51–54 traffic management system (TMS), 48

427

Index

Dispatching-control, 247–248 Display man–machine interface (DMI), 194, 197 Distance braking mode, 214, 215f District carrying capacity, 265–266 algorithm analysis, 410 average minimum train interval method, 275 calculation methods, 275–276, 410 coefficient removal method, 275 constraints, 399–401 definitions and symbols, 393–394 description of problems, 394–398 objective function, 398–399 parameters and operation scenes, 408–410 simulation method, 276 Driver advisory system for dispatcher (DAS-C), 129 Driver advisory system-onboard (DAS-O), 129 Driver’s information existing route confirmation method, 64–65 problems in existing route confirmation method, 65–66 signal display and driver control, 62–63 Dynamic control of train spacing, 213–218 Dynamic train interval control, 216

E

Electronic coding, 149 Emergency stop message processing, 196 ERTMS. See European Railway Traffic Management System (ERTMS) ETCS-3 level operation, 253 European Integrated Railway Wireless Enhancement Network (EIRENE), 80 European Railway Traffic Management System (ERTMS), 38–41, 133–136 European standard method, 201–203, 202f Execution process of CTCS-3I train control software, 197–199 Existing methods, for station carrying capacity improving capacity utilization, 391 improving theoretical carrying capacity, 392 reducing route locking and release times, 391 shortening throat length, 392 Expanding route information, for transport capacity improvement

by increasing driver’s information, 62–66 principle and feasibility analysis, 66–74 by signal display development, 57–62

F

Fixed approach locking section, 109–112

G

Genetic algorithm ATP protection curve algorithm, of CTCS-3I train control system, 204–206 signal point layout optimization model, 185–187, 185f

H

Headway in station on high-speed railways arrival-departure headway, 285 arrival headway, 284 calculation, 320–327 case study, 328–358 classification and calculation characteristics, 300–320 crossing headway, 284 departure-arrival headway, 285 existing calculation methods, 285–288 model solution algorithm, 327–328 opposite passing headway, 285 time-space graph of train tracking operation, 289–300 Headway in station types arrival train and departure train in opposite directions, 315 in same direction, 315 arrival train and passing train in opposite directions, 310 in same direction, 309 departure train and arrival train in opposite directions, 317 in same direction, 316 departure train and passing train in opposite directions, 313 in same direction, 312 operation direction combination, 305 operation state combination, 304 passing train and arrival train in opposite directions, 311 in same direction, 311 passing train and departure train in opposite directions, 314 in same direction, 314 route combination, 304, 305–306t set of headways in station, 318 two arrival trains

428

Index

Headway in station types (Continued) in opposite directions, 308 in same direction, 307 two departure trains in opposite directions, 309 in same direction, 308 two passing trains in opposite directions, 309 in same direction, 309 Hierarchical speed control curvilinear speed, 33 multistep speed control, 32 High Density European Traffic Management System (HD-ERTMS), 133–136 High-speed railway signal system intelligence technology automatic train operation, 92 centralized traffic control (CTC) system, 101–106 development status, 94–96 dispatch command, 92 EMU intelligent technology, 92f integrated intelligent scheduling, 97 intelligent driving, 97 maintenance, 93 Shift2rail Project IP plan, 94–95, 95f state perception, 96 vehicle-to-vehicle communication, 97 High-speed railway, train tracking interval time, 161–164, 162f

I

Initial population generation algorithm, 185, 186f Integrated traffic management with station signal system HD-ERTMS, 133–136 parallel control of high-speed railway, 136–143 traffic conflict resolution method, 127–133 Intentional decoupling, 257 Interlocking system, 41–42 communication efficiency, 46 computer interlocking, 44–45 digital computer interlocking, 46–47 full mechanical interlocking, 42–43 intelligent maintenance, 46 reducing data interaction, 46 relay interlocking, 43–44 shorter fault recovery time, 46 SIMIS-W system, 45–46

Interstation block artificial block, 25 automatic interstation block, 26 efficiency comparison of, 29 semiautomatic block, 26

J

Juridical recording unit (JRU), 194

L

Line transportation capacity, 8–11

M

MA. See Movement authority (MA) Man–machine interaction, 196 Manual blocking, 360 Model solution algorithm, 327–328 Movement authority (MA), 171, 212–222, 213f Moving block, 361 carry capacity, 196–197 principle, 189–192 safe distance, 191, 191f target point, 190, 190–191f train positioning technology, 189 Multi train synchronous control method, 171

O

Objective function, 323 On-board equipment of CTCS-3I train control system backtrack protection, 195 curve calculation synchronization technology, 195–196 data recording, 196 emergency stop message processing, 196 man–machine interaction, 196 slip and reverse protection, 195 speed measurement and ranging, 195 speed monitoring, 195 transponder information receiving and processing, 195 wireless communication management, 195 Optimization model ATP protection curve algorithm of CTCS-3I train control system, 203–204 block section and train route, 368–369 block section design, 177–187 movement authority (MA), 212–222 off-line safe train distance, 215

Index

Optimization model (Continued) overspeed protection curve based on train braking performance, 206–212 section signal point layout, 178–187 train tracking interval, 170–171

P

Parallel control of high-speed railway artificial HRS model, 140, 140f computational experimental platform, 142, 142f control and management for complex systems, 138–139, 138f emergency dispatching, 141–142 framework of parallel control system, 138–139f, 139–140 parallel execution, 142–143, 143f traffic management, 141 train operation, 141 Pure moving block (PMB), 172, 172f

Q

Quasimoving block, 361

R

Radio block center (RBC), 192, 197–198, 219–220 Radio transmission module (RTM), 194 Rail transit and transportation capacity, 4–8 diesel locomotives, 5 eight vertical and eight horizontal high-speed railway, 6f electric locomotives, 5 four vertical and four horizontal high-speed railway, 5f steam locomotives, 4–5 transmission and control methods, 7–8 Railway signaling and line capacity, 13–17 Railway Technical Management Regulations, 161, 163–164 Railway transportation stage, 2 RBC. See Radio block center (RBC) Relative moving block (RMB), 172 Relay coding, 149 Road, air, and pipeline transportation stage, 2 Route related information (RRI), 220–223

S

Safe train distance, 191, 191f definition of, 214 off-line calculation, 214

429

Section signal point layout constraint condition, 181–184 influencing factors, 178 limit length of track circuit, 178 line conditions, 178 model solving algorithm, 185–187 objective function, 180–181 optimization model, 180–187 signal display, 178 train braking distance, 178 Section speed control, 168–169 Segmentation release mode adjustment of time-space graph of train tracking operation, 378–382 for block sections, 369–370 feasibility and safety analysis, 374–377 necessity analysis, 370–374 reconstruction calculation model, 382–387 for routes, 370 station carrying capacity, 387–390 Semiautomatic blocking, 361 Shortening headway in station analysis of calculation, 414 Xuzhou East station after segmentation release, 413, 415–417t Shortening locking delay algorithm, 218–222, 219f Signal display, 178 color light signal, 57–58 development of, 60–62 evolution of, 58–60 Simulation method, 268, 269f, 276 Simulation verification, 71–74 Slip and reverse protection, 195 Solution algorithm branch and bound algorithm (B&B algorithm), 401–402 column generation technology, 402–405 process of branch and bound algorithm, 405–408 Space-interval method, 360 Speed and distance measurement unit (SDU), 194 Speed distance curve control mode, 16, 17f Speed ladder, 201, 203, 205–206 Speed measurement and ranging, 195 Speed monitoring, 195 Station carrying capacity arrival and departure tracks for passenger trains, 265 calculation methods, 268–274 direct calculation method, 274

430

Index

Station carrying capacity (Continued) formula method, 273 graphical method, 274 high-speed railway station, 265 idle time, 264 imbalance of arrival and departure of trains, 264 proportion of scenarios, 264 simulation method, 268 timetable graph compression method, 271 trains to occupy arrival and departure tracks, 264 Station operation refined management block time of train, 124–125, 124f holistic open mode, 125, 125f invading insulation joints, 124 segmental open mode, 125–126, 125f track circuit, 123 turnout, 123 Stop sign board (SSB), 165, 165f

T

Target speed monitoring section (TSM), 363 TC. See Track circuit (TC) TCC. See Train control center (TCC) Temporal-spatial network directed arcs, 396 nodes, 396 temporal-spatial path, 396, 398 Temporary speed restriction server (TSRS), 192 Throat length, 165 Time-interval method, 360 Time-space graph of train tracking operation characteristics of calculating headway in station, 319–320 in section, 290–291, 292f in station, 291–300 train occupation unit, 289 Timetable graph compression method, 271 Track circuit (TC), 192 AC-DC track circuit vs. frequency-shift track circuit, 79 4/8 information frequency-shift track circuit vs. ZPW-2000 track circuit, 79 limit length of, 178 UM71 vs. UM2000, 79 Track circuit adaptive coding method capacity, 158–159, 160f, 160t CTCS-3 algorithms, 154–156, 154–155f handling boundary values, 156–157

principle, 153, 154f safety, 157, 158f Track circuit identification (TCI), 154–156 Track circuit reader (TCR), 193–194 Tracking code sequence (TCS), 152 Trackside electronic unit, 193 Traffic conflict resolution method dispatcher advisory system, 129 rail control system (RCS), 132 railway traffic management, 127, 127f, 131f train conflict situation, 130f train state comparison, 131f Train arrival tracking interval, 162, 162f Train-centric CBTC system (TcCBTC), 227–229 Train control center (TCC), 192 control range and code direction, 154, 154f track circuit coding in section, 152 track circuit coding in station, 151 Train control information ATC digital track circuit, 78 control modes, 88–89t telegram type, 78t track circuits, 79 UM71 track circuit, 77 UM2000 track circuit, 77 vehicle-to-ground communication transmission, 80–83 ZPW-2000 track circuit, 77 Train deceleration, in advance algorithm, 168, 169f principle, 168, 168f Train departure tracking interval, 163, 163f Train dynamic adjustment strategy dynamic train interval control, 216 real-time adjustment of curve generation, 217 steps, 216 Train interface unit (TIU), 194 Train operation control system, 23–25 application, 30 automatic block, 26–28 braking mode, 31–41 driver priority control, 31 equipment priority control, 31 ground equipment, 25 GSM-R wireless communication system, 23 interlocking system, 41–47 interstation block, 25–26 space interval method, 25 structure diagram, 24f vehicle equipment, 23–25

Index

Train operation dispatching command system (TDCS), 14 Train operation organization speed control mode curve, 279 speed difference and proportion of trains, 279 stop schedule plans, 279 train operation district, 279 train operation sequence, 280 train speed over sections, 280 Train passing tracking interval, 163, 163f Train positioning technology, 189 Train section tracking interval, 161, 162f Train speed control mode, 16 Train synchronization control, 171–177 application, 174–177 minimum train interval under moving block mode, 171–172, 172f principle, 172–174 Train-to-train communication, 225–226 autonomous handling route, 232 cooperative control, 233–248 reduce communication link, 230 TACS system, 229 train-centric CBTC System (TcCBTC), 227–229 Urbalis Fluence, 230, 230f virtual coupling control system, 248–260 Train tracking interval for high-speed railway, 161–164, 162f operation process, 161–167 optimization, 170–171 section speed control, 168–169 time calculation, 164–167, 166–167t train synchronization control, 171–177 Train tracking operation in station adjacent arrival and departure trains, 300 adjacent arrival and passing trains, 295 adjacent arrival trains, 291 adjacent departure and arrival trains, 300 adjacent departure and passing trains, 295 adjacent departure trains, 291 adjacent passing and arrival trains, 295 adjacent passing and departure trains, 300 adjacent passing trains, 295 Transponder, 193 antenna, 194 information receiving and processing, 195 Transportation development comprehensive transportation stage, 3 railway transportation stage, 2

431

road, air, and pipeline transportation stage, 2 water transport stage, 1 Transportation management information system (TMIS), 14 Transportation organization and dispatching and line capacity, 17–20 Transport capacity improvement automatic train operation (ATO), 101–106 by increasing driver’s information, 62–66 intelligent dispatching system, 98–100 intelligent technology, 91–106 principle and feasibility analysis, 66–74 signal display development, 57–62 vehicle-to-ground transmission, 75–91 TRIVDE system, 66–68

U

Unintentional decoupling, 254 Urbalis Fluence, 230, 230f

V

Variable approach locking section hardware structure and basic workflow, 112–113 integrated traffic management, 127–143 length calculation, 113–114 passing capacity of station, 118–123 rules and deficiencies, 109–112 timing for setting route, 114–118 Vehicle–ground cooperation, 222–223 in abnormal scenarios, 222–223 in normal situations, 220, 221f shortening locking delay algorithm, 218–222, 219f Vehicle-to-ground communication transmission CBTC system, 80–83 China train operation control system (CTCS), 80 GSM-R technology, 80 waveguide data transmission, 83, 84f wireless antenna communication, 82, 83f Vehicle-to-vehicle communication, 258 CBTC system, 85–86 train control system, 84–85 transmission diagram, 87f Virtual coupling control system concept, 250 development, 248–254 ETCS-3 level operation, 253 freight transportation, 257

432

Index

Virtual coupling control system (Continued) group operation, 254 intentional decoupling, 254 operation problems, 260 principle, 253 security issues, 257–258 structure, 251 subway transport, 256 technical problems, 258–260 transport capacity of high-speed railway, 255 unintentional decoupling, 254 Virtual marshaling, 422–423 Vital computer (VC), 193

W

Water transport stage, 1 Waveguide data transmission, 83, 84f Wireless antenna communication, 82, 83f Wireless communication management, 195

Z

ZPW-2000A track circuit code sequence, 148, 151f electrical insulation, 148 low-frequency information codes, 148, 150t structure, 148–149, 149f