Safety Theory and Control Technology of High-Speed Train Operation

By Junfeng Wang

Safety Theory and Technology of High-Speed Train Operation puts forward solutions for train dispatching and signal control. Frequent railway incidents have threatened the safety of rail transport. In 2013, more than 12 trains collided. In the same year, a Spanish train derailed due to speed, and two of China’s high-speed trains collided. In 2016, Germany and Italy both experienced serious train collisions. Global railway security is essential. Many accidents are caused by train dispatching errors and signal system failure. Chinese high-speed railway has developed very quickly and at a very large scale. However, many issues reagrding safety has not been addressed. This book considers the issue from the perspective of a system. A train operation control system structure is put forward in order to ensure safety. Five key technologies (namely system-level fail-safe, parallel monitoring, completeness of train control data, data sharing and fusion and prevention of common errors in monitoring), are proposed. In order to prevent collision, over-speed, derailment, and rear-end collision accidents, the concept and corresponding parallel monitoring technology of five core control items (train route, speed, tracking interval, temporary speed limit, train running state) is proposed.

• Puts forward solutions for train dispatching and signal control
• Views high-speed train safety and technology from a systems-theory perspective
• Describes five key technologies to ensure safety
• Proposes five parallel monitoring technologies to prevent collision, over-speed, derailment and rear-end collision incidents
• Considers the very quick and large-scale development of Chinese high-speed rail

• Language: English
• Publisher: Academic Press
• Release date: Oct 24, 2017
• ISBN: 9780128133057

Junfeng Wang

Junfeng Wang is a Professor and the Vice Director of the State Key Laboratory of Rail Traffic Control and Safety, Beijing Jiaotong University. He received his Ph.D. degree from Beijing Jiaotong University, China; and has participated in several major projects on high-speed trains funded by the Chinese government in 2002. His research interests include intelligent transportation systems, communication-based train control, Radio Based Cab-Signaling, fault diagnosis, system reliability and safety, system-level fail-safe, mutual-discipline control studies in the high speed railway signaling system.

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Preface

Junfeng Wang

In the past 30 years, rail transport in China has undergone a number of tremendous improvements and changes. Locomotive trains, such as the steam locomotive, diesel locomotives, and electric locomotives, have been replaced by MU (Multiple Unit) trains. The average train speed has increased from around 50–60 km/h to 350 km/h. Signaling systems for the trains have been improved from only having ground control, to having both ground control and on-board control systems. (I have worked on a steam locomotive which did not have a speedometer!) These on-board signaling systems include a Computer Interlocking System, CTC (Centralized Traffic Control), and an ATP system which allow closed-loop control between vehicle and ground. Nevertheless, there is still room for improvement regarding railway safety from a global perspective. In 2016, serious train collision accidents have happened in Munich, Germany, Puglia, Italy, New York, United States, Semnan Province, Iran, Multan, Pakistan, and many more countries. In the same year, a number of major train derailment accidents also happened numerous places, including, Pukhrāyān, India, HuKun Railway, China, and Brooklyn, New York. There was the derailment and collision accident on the China Jiaoji line on April 28, 2008, the rear-end collision accident on the China Yong-wen line on July 23, 2013, and the speeding train that derailed in Spain on July 24, which all caused significant casualties. With major railway accidents happening around the globe, it is safe to say that railway safety all over the world, including developed countries, are yet to be improved. When analyzing the reason behind these accidents, most accidents are caused by errors in both controlling train operation and scheduling command. With the rapid development in railways, we are in desperate need of higher qualities of high-speed railway train safety control technologies. However, research on safety theories and control methods of high-speed train operation are far behind development. Therefore, this book offers both important theoretical and practical significance.

Targeting the existing problems and deficiencies of the current train operation control technologies, the book plays an important role in guiding and improving the safety of train operation control by proposing innovative theories and technical improvement. The main problems of the existing train operation control system include: (1) Some part of the system is not applicable for high-speed train operation safety requirements; (2) the signal system is a building block structure, not a one-time design based on the theory of system engineering; (3) the equipment-level and device-level fail-safe cannot meet the requirement of fail-safe; (4) the phenomenon of two pieces of skin between train scheduling command and train control operation; and (5) safety problems caused by personnel factors. This book applies system safety studies to solve the existing problems, based on system science and system engineering theory. This book makes a breakthrough in the traditional mode of thought and the barrier posed by traditional approaches. Theory system and framework of high-speed railway train operation safety are proposed aiming at the safety problems of self-discipline control technology, parallel monitoring technique for five core control items of train route, track interval, train speed, train safety temporary speed, and train running status is presented. The theory and implementation method of system-level fail-safe is put forward, the monitoring and early warning signs of train operation state and train intelligent auxiliary dispatching based on big data and key technologies of human factors safety are brought forward.

The book consists of 12 chapters. The first and second chapters conclude the development history on train operation safety and existing train control technologies. Chapters 3 to 10 are concerned with the following: Theory system and framework of high-speed railway train operation safety; The theory and approaches in system-level fail-safe; The technology of parallel monitoring; Integrity of train control data; Data sharing, fusion, and avoidance of common cause errors; Real-time monitoring and early warning signs of train running-state and operation behavior; Train Operation Control and Intelligent Dispatching; and Failure mechanism and risk control of train control. Finally, Chapters 11 and 12 introduce safety analysis methods for train control systems and safety evaluation methods of train control systems, respectively.

The book is applicable for readers in fields such as railway safety management and the safety control of trains. Typical readers would be the following: Safety management and technology personnel in train operations; Designers of railway signaling and standard setting; The test personnel and safety evaluation personnel; Manufacture of signaling equipment, management, and operation maintenance personnel; Researchers on the safety technology and next generation signaling technology on railway; Professional university teachers and students studying the railway field, and so on.

In the early 1980s, I started my first job as a crew member (assistant driver) on a locomotive after graduating with a major of train driver. There was a serious collision in the locomotive I had taken, resulting in casualties and property damage. After I experienced this accident, I deeply understood the importance of train operation safety and control. Therefore, I went on to study the profession of railway signaling instead of the former major and got the master’s degree in the field of railway transport automation and communications. After that, I obtained a doctorate in traffic information engineering and control.

Over the next 30 years, I was engaged with teaching and research work related to railway signaling. During this period, I hosted or participated in more than 20 research projects, published more than 20 papers on IEEE transactions on intelligent transportation systems, safety science, and articles in the Journal of Advanced Transportation, Journal of Transportation Engineering, Journal of the China Railway Society, and other journals. I also achieved 10 authorized invention patents. In 2006, I participated in the work of the signaling system technology introduction of the Chinese first high-speed railway Beijing-Tianjin passenger dedicated line and Chinese high-speed railway CTCS standard-setting. From 2008, Beijing Jiaotong University has been entrusted by the Ministry of Railways to train a large number of high-speed railway signal on-site technicians, and I was one of the main organizers and was responsible for the teaching of principles and technical specifications in CTCS-2 and CTCS-3. Since then, I have been working in the State Key of Rail Traffic Control and Safety and served as deputy director of the laboratory. The contents of this book are the summary and essence of my long-term railway, on-site practice and railway signal theory research and teaching results.

Some theoretical research contents in this book come from the National Natural Science Foundation Project High-speed railway signaling system-level fail-safe theory and method, independent projects of State Key of Rail Traffic Control and Safety and so on. The grant of the project has played an important role in the publication of this book. I am particularly indebted to the students who were at Beijing Jiaotong University while I was writing this book and made an important contribution to the compilation, processing of material, entering and translation of this book: Lijiang Dai, Wenli Guo, Peng Xu, Hao Liu, Yunpeng Ma, Qi Liu, Minghui Li, Wu Wei, and so on. During the process of writing this book, I have also received encouragement and support from my wife Chen Wei, daughter Wanrong Wang, younger brother Jungang Wang, and my colleagues and manager. I express my heartfelt thanks to them all.

This book must have a lot of deficiencies due to the constraint of knowledge and time, so I earnestly urge readers to contribute their criticism and correction.

March 1, 2017

Chapter 1

The History of Train Operation Safety Development

Abstract

This chapter analyzes the history of safety developments for the operation of trains. First, it elaborates the initial development course of railway signals, summarizes the major train safety accidents, and analyzes the causes and lessons of train accidents. The chapter then analyzes problems in the existing signal system and the traditional concept of signal security, pointing out that the current situation of the safe operation of the train and the space for research and development. Finally, it analyzes and compares the international train safety system with China’s system.

Keywords

Development course; train accident; train safety status; train safety system

1.1 The Development History of Railway Signal

In 1796, the British inventor Richard Trevithick created the first steam engine model (Fig. 1.1). This is considered to be the dawn of the railway transportation, with further improvements that followed quickly [1]. In 1825, the British used a steam locomotive to carry passengers as a replacement for a train drawn with a horse. On September 24, 1825, the first manned train was declared and put into experiment. Fig. 1.2A represents the original method (train drawn by a horse), and Fig. 1.2B represents the manned steam locomotive.

Figure 1.1 Steam locomotive manufactured in 1796.

Figure 1.2 (A) A horse-drawn train and (B) a manned steam locomotive.

Because a train can only run on a fixed track, any obstruction or thing on the track can lead to dire consequences. Moreover, weather conditions such as heavy fog as well as other factors, such as unfit driver, can lead to major problems. Now, with the earliest trains a lot of hidden dangers can be seen from the first compartment of the initial train. Therefore, while the earliest stream train is running, a man on a horse holding a signal flag was required to guide the train go forward (Fig. 1.3). With the increase of the train speed, this way was eliminated rapidly.

Figure 1.3 A man on a horse holding a signal flag guiding the train.

In 1832, the United States started using a spherical stationary signal device in the Newcastle–France railway line to transmit the information between stations. If the train arrived on time, a white ball was hung; if the train was late, a black ball would be hung. This kind of signal machine was used for every 5 km. The railway staff lookout used a telescope and transmitted information along the line in order to convey the message of the train operation. In 1841, the British inventor C.H. Gregory invented a rectangular arm plate annunciator that was mounted on a high post (Fig. 1.4). When the arm is in a horizontal position, it indicates parking; a tilt 45 degrees downward would indicate that the train can continue on. Afterward, a color light annunciator was introduced and used for night-driving needs. The early signal control was manipulated by a person standing under the column. Later, this method was connected to the conductor in the duty room to operate, which lightened the worker’s labor intensity.

Figure 1.4 (A) The early semaphore and (B) the electric control of the semaphore first used in 1882.

In 1872, an American named William Robinson invented the track circuit, began a new era of automatic signal control [1]. The previous railway signals mainly solved the basic vision problem. Ground signals provide visual signals to drivers, but due to the influence of terrain and climate, drivers could not always notice the semaphore signal in the distance, thus there’s a danger of overrunning of signals. Therefore, the cab signal device was invented, and the visual signal of the ground was introduced into the cab to improve the condition of the driver’s visual field. However, the cab signal cannot prevent the danger that might occur when the safety of trains is threatened by an inattentive driver or one who is caught off guard. So the automatic train stop (ATS) was developed. Its function is to force the train to stop when the ground signal forbidden command was not accepted by the driver. With the increase of train speed, especially with the development of high-speed railway, the ATP was developed and became widely used in order to overcome overturned accidents that resulted from train over-speed. With the development of automatic control technology and other technologies, the automatic train control system was used for the rail transit system [2]. As a consequence, the railway signal has evolved from the original vision signal into a closed-loop automatic control system.

In order to improve transport capacity, traffic density increased gradually, but in 1888, a two-car collision occurred on the single-track railway in Lake Erie, New York (Fig. 1.5). As a consequence, it became urgent to improve the safety of the signal. In the earliest days of train travel, a time-interval method was used: the follow-up train must keep a certain time interval from the forward train, in order to avoid the occurrence of two-car collision. Therefore, a signal device is set up at the exit of the station, which has two circular graphs, one painted with a white circle and another painted with a red circle (Fig. 1.6). If the driver saw the white circle was shielded, that is, only the red one was displayed, he had to stop; if he can only see the white circle but didn’t see the red one, he could drive forward. There’s also a timer above the signal board in which driver can see how much time was left the before train departed. From that a determination was made on whether or not the distance between the trains was safe and to move forward. This puts forward the problem of a safe driving distance, which produces the block technology and the relevant section signal technology. In 1851 the British subsequently implemented a block system using a telegraph. The section signal technology was developed through a telephone, the train staff, and an electric tablet block system, and then to the semiautomatic block system, and then to an automatic block system.

Figure 1.5 The two-car collision in the United States, 1888.

Figure 1.6 Red (black in print version)/white circle and the interval clock.

The safe operation of a train not only needs to control the speed and interval in a route, but also needs to be controlled at the station where the trains cross. There are a number of lines in the station, all connected by a switch at the ends. Different routes are formed according to the different positions of the switch, such as whether the train or team can drive into the route or not. If the signal displayed indicates that a train or a team is shunting into a track, but the opening position is on another track, this could cause a dangerous accident. In order to ensure safety, it is necessary to have a constraint relationship among the signal, route, and switch; this relationship is called interlocking [3]. When William J. Sax first invented the mechanical interlocking in 1856, the interlocking technology has experienced mechanical technology, electrical technology, and relay technology era, and now the computer-based interlocking has replaced the relay interlocking in the high-speed railway [4].

Improvement of the efficiency of railway transportation not only needs a good interlock, block, and train-control equipment, but also needs a good command and dispatching system. Before the informatization of railway dispatching systems, the traditional manual mode by the dispatcher was to use a telephone, a diagram, and a pen to establish the operation plan and organize traffic. In this way, the scheduling efficiency is very low, which limits the improvement of transportation efficiency and affects the development of railway capacity. The US railway employed its first scheduling centralized control device in 1927. This device makes the dispatching center master the train dynamic within the jurisdiction section in real time, and can carry out the centralized control of the signal equipment. After decades of efforts, the train-scheduling system has experienced the development stage of scheduling supervision, traditional DIMS, TDCS, and CTC scheduling. Nowadays, the command and dispatching system has integrated lots of advanced information technology, such as computers, communication, and automatic control. All of this has become the core system of modern railway transportation organization and operation management [5].

After the 1950s, science and technology developed rapidly: computer technology, network technology, modern communication technology, automatic control technology, and new alloy materials, manufacturing, intelligent transportation, and information security technology; and other high technology has accelerated the development of all facts of society, economic and otherwise. These new technologies become the soil for the cultivation of high-speed railways, and the high-speed railway is the inevitable product of social and economic development [6].

In 1964, Japan built the world’s first high-speed railway: the Tokaido Shinkansen. It set a good example for the development of high-speed railway in the world and announced the launch of a new, high-speed era for train travel. In 1981, France built the new trunk line of TGV to the southeast with highest speed of 270 km, which opened up a new way to build high-speed railways at low cost and push the construction of high-speed railways to a new level. These two new lines are not only a symbol of the development of high-speed railways, but also well known for the social and economic benefits, advanced technical equipment, and excellent passenger service worldwide.

The signal and control system for high-speed railway is the key technology and equipment to ensure the safe operation of high-speed trains and to improve the efficiency of transport. In the process of the development of high-speed railways, the world over attaches great importance to the research and development of high-speed railway signals and control technology. A traffic command, train operation control, and management automation system, along with a combination of computer technology, communication technology, and control technology, marks the modernization of a national rail transit technology and equipment [7].

Compared with a normal-speed railway, the main characteristics of high-speed railway are [8]:

1. The train control center can adjust the operation of the train according to the running state of the train and the one before. The ground signal can be replaced by the cab signal to control the train operation.

2. The amount of vehicle-ground control data is increased to meet the needs of train safety tracking interval control and train braking. If the existing analog track circuit does not meet the requirements, the use of GSM-R wireless information transmission can solve the problem.

3. The train control center can get the state of information of all the trains running on the line in real time. By the interface with CTC or TDCS, the system can realize the computer-aided train adjustment, adjust an operation diagram automatically, and enhance the management ability of railway transportation.

Speed is the most important significant aspect of high-speed railway technology, the highest operating speed of high-speed trains in France, Japan, Germany, Spain, and Italy have reached up to 350, 300, 330, 270, and 300 km. The main technical characteristics of high-speed train signal system are embodied in train control information, train tracking interval and time interval, ATP control mode, and so on. Usually, the train control information mainly refers to the information transmission between the ground equipment and the on-board equipment. The amount of information and the real-time performance of the train control information should meet the requirements of different speeds, different densities, different modes of transportation, and different train control modes, so the amount is very large. A hierarchical staged speed control code is using in the existing three-display and four-display signal systems, but high-speed railways adopt speed-target-distance mode curves; as a result, the length of the block partition and calculating formula of train tracking interval is no longer suitable for the high-speed railway, and the length of the block partition must be increased.

The train control system for high-speed railways in the world mainly includes ERTMS/ETCS system in Europe, the LZB system used in Germany and Spain’s high-speed railway, the TVM300 and TVM430 system used in French TGV railway, a new trunk line ATC in Japan, a nine-yard automatic train control system for Italy’s high-speed railway, the EBICA900 system of Swedish railway, and CTCS-2 and CTCS-3 system of China high-speed railway.

High-speed rail constantly updates the traffic safety record on the landing, and creates a new record on speed train tests. A French high-speed train reached a speed of 574.8 km/h in a driving test on April 3, 2007; it broke the world record of 515.3 km set by a French high-speed train in 1990 [9]. Nowadays, the basic system of high-speed railway signals has matured, and the safety of signal equipment has also been recognized. It can be seen from the above that the signal is generated and developed because of the security needs.

1.2 Railway Accidents and Causes

In the past ten years, it has been discovered that railway traffic safety is still in a state of fluctuation, and because of extraordinarily serious accidents that still occur, passenger traffic safety still faces a major challenge. A statistical data of railway accidents of 28 European countries shows: 432 major accidents occurred from 1980 to 2013. Accidents due to over-speeding, signal or scheduling errors, was total 151, which is about 34%. This proportion is larger for high-speed railways, and the operation control is more and more important to ensure the safety of the train operation. The concept in traditional train safety and control technology cannot satisfy the needs of high-speed train safety.

1.2.1 Major accidents at home and abroad

Today, many similar accidents still repeat themselves. The fool to bleed for lessons, but a wise man learn lessons to stop the bleeding. Therefore, we should sum up the experience and lessons, analyze accidents, and sum up the regularity of things to guide us toward safer conditions.

1.2.1.1 Train derailment accidents

Generally speaking, train derailments are common. The specific causes of train derailment are mainly due to track, locomotive, train control issues, and other factors, including trains that over-speed at the bend, are out of control going downhill, thereby exceeding the temporary speed restriction, and have poor brake performance. Here are a few typical accident cases (Fig. 1.7).

1. Over-speed leads to derailment: US 5–12 accident, Spain 7–24 derailment, China 4–28 accident

On the evening of May 12, 2015, at about 9:30, a serious derailment occurred in Amtrak’s 188 train from Washington to New York, when it traveled to northern Philadelphia in Pennsylvania. All seven carriages derailed, causing seven deaths, and injuries to more than 200 people. The route is known as the Eastern Corridor of New York, which connects several large cities in eastern corridor including Boston, Washington, New York, and Philadelphia with more than 2200 trains passing this route every day. The cause of the accident announced by the US Railway Bureau is that the train speed was 100 mph while the accident occurred, exceeding the designated limit speed of 50 mph (Fig. 1.8).

On July 24, 2013, in Spain, a passenger train derailment accident occurred, causing 80 deaths and more than 170 injuries. This accident occurred at around 8:42 p.m., on a train that was going from Madrid to the northern city of Rolle. It was the third most serious rail accident in Spain, and one of the worst train accidents in the world since 2013. The train traveled from Madrid to Galicia for Rolle, carrying more than 220 passengers. At 8:42 that evening, when it traveled to a corner 3 km away from the capital of Galicia Santiago de Compostela station, it suddenly derailed. When the train entered the curve, which had a speed limit of 80 km/h, the speed was once as high as 192 km/h. The investigators said the braking system was launched just before the derailment.

On April 28, 2008, from Beijing to Qingdao, on the Jinan Railway Bureau tube Jiaoji downlink Wangcun to Zhoucun East 290.800 km, due to speeding, the T195 passenger train incurred a serious accident. Its 9–17 vehicles derailed and invaded the uplink rail and collided with train No. 2254, killing 72 people and injuring 416 (Fig. 1.9).

Cause of the accident: The most direct reason for the accident is the speeding of the T195 train, with 51 km/h above the temporary restricted speed. After the analysis was completed, some other reasons discovered for the accident include:

a. The implementation process to replace the temporary speed restriction order with documents had been treated in an extremely unserious way. The railway Bureau of Jinan, after publishing The notification for adjustment of operation diagram of Jiaoji line during construction, canceled the speed limit order for many places on a condition that did not assure whether the related parties had received the notification or not.

b. The Bureau forgot to issue the order for a temporary speed restriction. The Jinan Bureau reissued the No. 4444 command of a speed limit for 80 km/h again on April 28 when the dispatcher of Jinan Bureau received the data that showed there was a mismatch in speed limit between the monitor machine and the command paper. But the command did not reach the trainman on the T195.

c. The driver of the T195 ran the train with a speed for 131 km/h and had not noticed the temporary speed restriction command written in black on the yellow board, which was situated by the rail, losing the last chance to prevent the accident from happenning.

In this accident, it is showed that all the drivers, dispatchers, station operators, the line maintenance department, and the monitoring device did not strictly follow the temporary speed restriction order, which caused the accident.

2. The derailment was caused by obstacles: an accident in France on July 12

At 5 p.m., July 12, 2013, a train of the French national railway company that ran from Paris to Limoges derailed in the Bretigny train station in Essonne province, which is about 25 km away from Paris, causing the death of six people and injuring more than 30. The accident is the most serious one in the past 25 years. The main reason for the accident was that a piece of track joint splint dropped on the rail, which prevented the train from passing. After its derailment, the train rushed into the station with high speed and broke into two parts. Four carriages out of seven derailed and two of them fell on to the rail while one of the other two fell between the railway and the platform (Fig. 1.10).

3. The derailment caused by bad braking while marshaling: accident in the United States on June 20, 2003.

Figure 1.7 Scene of US May 12 accident.

Figure 1.8 Scene of Spain July 24 derailment.

Figure 1.9 Scene of China April 28 accident.

Figure 1.10 Scene of the July 12 accident in France.

On June 20, 2003, a train full of logs derailed near Los Angeles in the United States, causing the logs to roll into residential areas on both sides of the railway. At least 12 people were hit by the accident, one of them was seriously injured. Also, many houses were destroyed.

The accident happened when carriages were reorganized. At that time, some carriages lost control and caused sliping. The staff transferred the carriages to the reserve rail when it was noticed that the situation became risky, but the derailment occurred at this time. A total of 18 carriages scattered on both sides of the track, a large number of logs piled up in the vicinity of the scene. Fortunately, no fire and other accidents were caused.

1.2.1.2 The collision accident between trains

1. In United States: collision and explosion between freight trains

Around 2:00 p.m. local time on December 30, 2013, a train which transferred crude oil, with a total of 104 carriages and up to 1600 m long, collided with another freight train that was transferring soybeans. The place where the accident happened was around 1.6 km away from Cassel County, North Dakota. A huge fireball and black smoke raised into the sky. Faced with such a disaster, firefighters looked helpless and could only watch the fire burn out the crude oil. However, it took 12 h to burn out all the crude oil. Fortunately, no one died in this accident (Fig. 1.11).

Figure 1.11 Scene of December 30 accident in the United States.

The cause of the accident is that some carriages of the train, which carried soybean, derailed near an ethanol factory resulting in the collision with the train carrying crude oil.

2. Switzerland: collision between passenger trains

At 6:45 p.m., July 29, 2013, an arriving train collided with a leaving one in the Lagrange-Maernan station, which is 31 km away in southwestern Berne. The photos taken from the scene showed that some carriages derailed because of the collision. The two trains were heading for Lausanne and Payerne, respectively. There were 46 people on the train. This accident caused one death and 26 injuries, and five of them were seriously injured. One probable cause for the accident is that one train arriving late a little or the other one departing early (Fig. 1.12).

3. North Korea: two trains collided with each other and caused a violent explosion

Figure 1.12 Scene of the Swiss accident on July 29, 2013.

At about 2:00 p.m. on April 22, 2004 two trains, one carrying ammonium nitrate and the other carrying oil and natural gas, collided in the Longchuan Railway Station (50 km north of Pyongyang, which is the capital of the DPRK, in the northwest of the DPRK), causing a violent explosion and a conflagration causing the death of 154 people and injuring more than 1300. In addition to casualties, the explosion also destroyed many buildings nearby while the scene of the accident almost turned into a ruin. According to the data of incomplete statistics, 1850 houses were completely destroyed, 6350 housing units were partially damaged, and 12 public buildings were destroyed.

The cause for the accident is that the related staff neglected their duties and did not exercise them properly. The train rushed into the transmission pole and busted out some sparks, causing the disaster.

1.2.1.3 The rear-end accidents of trains

It is still very difficult for the public to recover from the pain of the serious Yong-Wen Line train accident on July 23, 2011. The severe accident sobered people who were excited about the leap forward to high-speed rail. It is worthwhile to analyze the July 23 rear-end accident as a way to help the public realize the importance of safety.

1. The whole story of the accident

On July 23, at roughly 8:30 p.m., the CRH train D301, running from Beijing South to Fuzhou, crashed into rear-end of the CRH train D3115, which was traveling from Hangzhou to Fuzhou South. The accident happened between Yongjia station to Wenzhou south station on Yong-Wen line. Four carriages fell off the viaduct. The accident killed 40 people and injured about 200 people. The driver of CRH D301 died on the spot. His chest was pierced through by the brake handle. It can be deducted that the driver tried to stop the train when he saw the former train, but it was too late. The accident caused an interruption of traffic for 32 h and 35 min and a direct economic loss up to 193.7165 million yuan.

The conductor of D3115, Jiang Xiaomei, who later accepted an interview with the media, said the train was about 5 min late. She recalled that the train came into a thunderstorm after setting out from Wenling station and had to slow down. After arriving in Yongjia station, the train temporarily parked for more than 20 min. She heard the driver tell the vehicle mechanic in the walkie-talkie that the train could not move because there was no signal indication resulting from bad weather on that day.

2. The cause of the accident

LKD2-T1 type train control center equipment of China Railway Signal & Communication Corporation (CRSC) has serious design flaws and significant safety hazards. When the fuse (F2) that was mounted in the power supply of Wenzhou South Station Train Control Center’s acquisition drive circuit unit was hit by lightning and had blown, the acquisition of data was no longer updated, the track circuit code and signal displayed in the wrong mode to indicate that the train is in an unsafe state. Lightning also caused 5829AG track circuit transmitter and a train control center communication failure, so that the ATP of the train D3115, starting from the Yongjia station to Wenzhou South Station, automatically triggered braking system, and the train D3115 stopped in the 5829AG section. Due to an abnormal track circuit code, the driver finally transitioned control mode of ATP to on sight (OS) mode with a speed of less than 20 km/h to a slow pace into Wenzhou South Station, but failed to exit the 5829 blocking in a timely manner. Due to the Wenzhou South Station train control center’s failure to collect the D3115 train in the 5829AG section of the occupation status information, the 5829 block partition and follow-up two-block partition under the control of Wenzhou South Station Train Control Center displayed the green light incorrectly, sending train-free code to the train D301, leading train D301 to drive into the 5829AG section occupied by train D3115 causing a rear-end collision.

3. Cause analysis

a. Red band failure

Red band means that the corresponding block section is occupied by one train. D301 was the rear-end train and D3115 was the former train. From the moment of arrival in Yongjia station, dislocation had already begun. According to a normal situation, the D301 should not stop at the Yongjia station and should run in front of D3115, but contrary to normal situation its being late. Moreover, it was forced to stay in Yongjia station because of the presence of red band caused by the occupation of D3115.

To some extent, the red band is the origin of the accident. This is not the first Chinese railway with red band with a rear-end accident [10]. On April 11, 2006, train T159, which is bound from Qingdao to Guangzhou East, crashed into rear-end of the stationary train 1017, running from Wuchang to Shantou, at LongChuan section. The last carriage of train 1017 is used for the crew resting, two cabin crewmembers died and more than 20 people were injured.

b. Scheduling error

Red band will certainly bring trouble to the console to determine the road traffic control, but as one person pointed out from the Shanghai Railway Bureau, if things had been in accordance with the normal scheduling and traffic regulations, the accident could have been avoided. Under the condition that the red band fault is not handled, the dispatcher forcefully gives the command of departure, for the purpose that the overdue train can run on time finally by departing as soon as possible. The Shanghai Railway Bureau official said, The D301 has been delayed and so we would like to catch up. There are problems with scheduling.

c. Signal error

A fatal error led to simple software design, Wenzhou train control center (TCC) cannot in real-time acquire external data and transmitted error information to centralized traffic control (CTC) system. The on-board equipment of ATP on D301 received the wrong signal which is considered to be normal and D301 still run at normal speed. After a moment, D301 had a rear-end collision with the preceding train D3115, leading to 40 deaths.

In a number of professional views, exposure to software design defects in the accident belong to relatively low-level errors. There are manufacturers of different security requirements, but the ‘fail-safe’ is the most basic principle; the design absolutely should not be such a problem, a China Academy of Railway Sciences expert said. He found it difficult to understand why the talented people under the CRSC could make such a big mistake. He guessed that the designers lacked experience and did not think of this possibility. The designers were focused on the hardware and not paid enough attention to the structure design of software.

d. Automatic protection failure

In fact, both the ATP system and the LKJ system need to use the ground train control system equipment information to know whether there is one train in a certain distance ahead. The ATP system and the LKJ system are powerless when the information of ground signaling equipment is lost. At that moment it was the ground signal that is out of