The Technical Cause of High-speed Railway Disturbance: An Impossible Accident

The core personnel of the railway system introduced that the cause of the “7.23” motor vehicle rear-end collision accident was initially identified and was only to be issued by the relevant authorities.

The design problem of the ground equipment of the signal system itself caused the failure caused by the lightning strike to escalate, the red code became green code, the green light signal was incorrectly sent out, and the D301 was led back to the front.

Starting at 20:25 on the 23rd, a series of plausible complex schedules actually placed the two trains on the dangerous edge of the cliff, and the breakdown of the signal equipment eventually pushed the two cars off the cliff.

"Red light must appear"

Five days after the incident, Shou Dashan was still puzzled by the scene he saw: Why did the train in front stop suddenly?

Shou Dashan is one of the local witnesses of the “7.23” car rear-end accident. The accident took place in Xiacing Village, Shuangyu Township, Wenzhou, which is a “village in the city” in the suburbs of Wenzhou. The villagers gathered here with migrant workers who were several times the villagers. Shou Dashan from Suzhou, Anhui, works in a shoe factory and his factory is less than 100 meters away from the accident site.

"The car in front of" is D3115. At 20:23 on July 23, the train stopped on the viaduct. At the Yongjia station 12 kilometers after that, another D301 train was in motion. The two-car rear-end tragedy took place, as did the final eight minutes.

An online “training record” of trains describes in detail the complicated and thrilling schedules before the accident. Southern Weekend confirmed the accuracy of this record with a number of relevant experts and relevant persons in charge of the Wenzhou South Railway Station.

Based on this schedule record, you can restore the driving status of the two vehicles. Prior to this, Wenzhou South Station found that the direction of Yongjia down to the car to three close (close to the station's three blocked zones, about 5-6 km) circuit appeared red band (no reason to all show a red light failure). Therefore, both the Wenzhou South Railway Station and the Yongjia Station were dispatched to the station control station.

It is understood that CTCS-2 train control equipment is used for the accident line. Under normal circumstances, the following control equipment will divide the railway into several sections. One section can theoretically be placed in only one train. After the train enters, the tail lamp of the section will display red light. At the same time, the railway signal design adopts the "fault-oriented security principle", that is, if there is a failure problem, it automatically leads to the technical principle of the safe side. If the ground signal system is damaged and train information cannot be found, the zone will always show a red light.

Both the D3115 and the D301 have now been scheduled to go into a very-station-controlled mode of operation. The very-station-control means that the zone signal fails, but for efficiency reasons, it is necessary to maintain a portion of the traffic. In layman's terms, both vehicles will be driven by dispatch authorization and artificially combined signals.

Post-hoc analysis is most likely due to double errors in the combination of dispatch and signal, leading to rear-end.

That night for thunderstorms, earlier from the railroads, D3115 stopped because of a lightning strike. "After being struck by lightning, the EMU lost its power and caused a rear-end collision."

“Lightning Strike” said that it was widely questioned that even if the front of the train lost power due to a lightning strike, the rear car should not be hit by the automatic car protection system (ATP) but it must be at a certain distance from it. Automatic braking. Guo Jin, deputy dean of the School of Information Science and Technology at Southwest Jiaotong University, told the reporter that “Under normal conditions, because the speed of the motor vehicle is very fast, people cannot control the speed of the vehicle. Instead, the ATP equipment automatically controls the safety of the vehicle speed.”

In fact, of the three accidents that the Beijing-Shanghai high-speed rail had just opened, one incident was caused by thunderstorms. However, according to the analysis of experts, it is wind rather than thunder. A train driver with 20 years of driving experience told the Southern Weekend reporter that he had never touched a parking accident caused by a lightning strike during his driving career.

The D3115's driving status was analyzed. Before stopping, the D3115 departed from Yongjia Station and drove 12 kilometers within 8 minutes. The average speed was nearly 100 kilometers and the maximum speed was close to 200 kilometers. It is clear that the loss of power from lightning strikes cannot be established.

According to Shou Dashan, the front train (D3115) slowly reached the viaduct and stopped. Although there are dozens of vehicles on the train every day, the situation of parking has never happened before. Shou Dashan's heart rises ominously: What should you do?

At 20:25, D3115 started slowly again. In accordance with the authorization of the dispatch, the driver will drive in a red light in a visual mode, according to the regulation speed of 20 kilometers per hour. In 6 minutes, the train moved forward 2 kilometers.

Almost at the same time when the D3115 was restarted, the D301 at the rear Yongjia station also received a dispatch order to restart the car. However, unlike the instructions given to the D3115, the dispatch did not authorize the D301 to look at the red light. Instead, it touched the red belt and then followed the signal. In other words, when the signal showed a red light, the D301 must stop and wait.

The idea of ​​dispatching is to allow the D3115 to first see the red light passing through the red band, and the D301 to stop in front of the red band. After confirming that the D3115 has entered the station, the D301 is then authorized to pass the red band.

The key here is that the signal of the rear zone of the D3115 must be red, so that the D301 will stop by the signal.

In the scheduling plan, that red light will naturally appear - the entire signal system is being overhauled, and the red light must be displayed before the repair. The red light must also appear. It has actually become the last barrier between the two giants D3115 and D301.

On July 24, 2011, the air rescue team of the Chongqing-Cangnan County Air Emergency Rescue Center aerialized the Wenzhou train derailment accident. (Chen Bin/Figure)

Scheduling "hidden rules"

The passenger on D301 Fu Lijuan originally planned to take the Z60 and see a train from Beijing to Fuzhou. However, she found that after the high-speed rail was opened, he could not buy the ticket for this vehicle. She can only spend more than half of her money to buy D301 second-class tickets.

The D301 has gone through several sections of different lines before the Beijing-Shanghai high-speed rail before the Beijing-Shanghai. However, in Fu Lijuan’s view, on the Beijing-Shanghai high-speed rail line, the D301 seems to be a “second-class citizen”: “It started late after Jinan, and it was half an hour late to Nanjing”. Passengers who have long-term experience in driving tell Fu Lijuan that this is because the speed and punctuality rate of the high-speed rail must be ensured on the Beijing-Shanghai high-speed rail line, and the EMU must give way to the high-speed rail.

The Southern Weekend reporter found on the map of the train that the longest stop time on the Beijing-Shanghai line was 25 minutes. This is extremely rare for EMUs. Before the “7.23” rear-end collision incident, the Beijing-Shanghai high-speed rail was suffering criticism, and three outages occurred within four days after the opening, resulting in a large-scale outage of the high-speed rail.

In the complaints of passengers, D301 drove all the way through the Beijing-Shanghai line, past Shanghai and Hangzhou, and then entered the busy Yuwen railway line.

The Wenzhou-Guangzhou Railway completed in 2008 opened an EMU in October 2009. In a short period of one and a half years, the number of trains opened to traffic increased from 7 pairs to 30 pairs. Many motor vehicles are within 10 minutes of each other. It is clear to those in the industry that the more trips, the shorter the interval, the greater the difficulty and pressure of railway dispatch.

D301 passengers also have difficulty understanding parking at Yongjia station. Actually, it does not need to stop at Yongjia.

Also strange is the passenger of the D3115 car number 16 Song Jianxin. The train he took was shortly after Yongjia entered the station, and the next lane quickly drove another D301. Song Jianxin paid attention to this car because he found that the car was a sleeper, but passengers were sitting.

The fact that D3115 drove away before D301 had caused widespread questioning later on - according to the train schedule, it should have been behind D301.

The train driver mentioned earlier explained to the Southern Weekend reporter that the traffic arrangement should be decided by the train dispatcher at the Shanghai Railway Bureau. It also meets the “hidden rules” of the railway system: D301 starts from the Jinan Bureau rather than the Shanghai Bureau, and statistics The indicator of the late train is based on the number of turns rather than the lateness. Since D301 is late, the dispatcher simply makes it a bit late and gives way to D3115 in an effort to ensure that the latter is not delayed. Although D301 will be delayed more time, statistically, there are only a few delays.

In addition, Mr. Xu, a senior moderator of the Railway Forum, said that after the rear-end collision incident on the Beijing-Kowloon Railway in 2006, the Ministry of Railways had made regulations that if a signal failure occurred, it would be handled as an inter-station obstruction. Room only allows one car to pass. Specific to the incident, that is, after allowing D3115 to leave from Yongjia, D301 never leaves before it reaches Wenzhou South Railway Station. However, on the contrary, the rear vehicle will leave before the front vehicle has arrived.

Mr. Xu believes that the reason why the dispatcher violated the rules to release the D301 may not only save the whole process time, but also be too superstitious about ATP. He thought that with this system, the two vehicles would not be able to rush to the end.

The disaster factor seems to have originated from this order adjustment, which has led to the subsequent two vehicles must pass through the Wenzhou South Station in a complex and unconventional manner. D3115 left at Yongjia Station at 20:15 that night. After 9 minutes, at 20:24, D301 exits from Yongjia Station along the same line. From now on, every stoppage and start of the two vehicles will affect the occurrence of a disaster.

The most critical part has been an accident

For any railway professional, collisions with EMUs are incredible. Because the car is equipped with an automatic protection system (ATP), if the rear car is approaching the front car, the system will automatically cause the car to stop, and the driver "is just not going to hit it." According to the “Oriental Morning Post” report, Wang Mengshu, academician of the Chinese Academy of Engineering and a senior adviser on national railway construction, said that China’s high-speed rail is very successful in controlling systems and signaling systems, and can guarantee that there will be no rear-end rear-end collisions.

So how did this incredible accident happen? The Southern Weekend reporter learned from the core personnel of the railway system that the cause of the accident has been basically ascertained, and that dispatch has an insurmountable responsibility, and the signal system is also the most deadly mistake at the most critical moment.

Back at 20:25 before the disaster, D3115 began to visually slow through the red band.

According to Guo Jin, deputy dean of the School of Information Science and Technology at Southwest Jiaotong University and an expert on the signal system, it is normal for the authorized trains to encounter the red light and change to the visual mode after standing and controlling. Although there is a problem with the ground signal system, it is also a signal failure. However, this situation is also within the design framework of the railroad train control system, so the D3115 has no problem with speed limits up to 20 kilometers after contacting the dispatcher.

But why did the D301 come from behind the D3115? Why did the "red light that must appear" disappear at the most critical moment?

According to the preliminary cause of the accident disclosed by the core personnel inside the railway system, when the two vehicles were moving forward at the same time, the thunder and lightning interrupted the insurance of the ground equipment of a railway signal system at the temperature line. According to the requirements, the ground equipment should be “guided to safety” after a failure. That is, “red signal” is issued; however, due to problems in the circuit design of the ground equipment itself, the result is an upgrade of the fault, an error in the bypass circuit, a green code in the red code, that is, a “green signal”, which should automatically light up after a fault. The parking red light turned into a traffic light.

According to the inside information of the railway system, the company responsible for the circuit design of the ground equipment at the accident section is the China Railway Communication Signal Group. The “pass number” is the predator of the railway signal field.

At present, all roads are urgently changing the circuit design. The Ministry of Railways estimates that the entire circuit can be modified within one or two days. However, the person concerned was concerned that due to the problems caused by the immature design, it was uncertain whether there were other design flaws besides the failure.

In addition, in addition to this technical reason, the railway system believes there should be other human factors superimposed to cause the "7.23" EMU tragedy, especially the scheduling problem that has been widely questioned.

On July 25, the speech of the newly appointed Shanghai Railway Administration Director An Lusheng at the video and teleconference of the Bureau to some extent confirmed the news obtained at Southern Weekend. Ann mentioned in the "emphasis" point: "When the equipment fails, ... if necessary, take measures to stop." "...there is a red belt, the first tentatively scheduled traffic between stations; When the centralized section is changed from the dispatching section to the extraordinary station control, it must be approved by the on-duty director of the dispatching department and confirmed that the station-control personnel must be transferred to the post before they can be converted.” “...We must treat the equipment failure as a serious accident.... The department should not blindly direct traffic."

In addition, after the accident, the Shanghai Railway Bureau, in addition to former director Long Jing, deputy director He Shengli was also removed from office – the area in charge of which is the public works and telecommunications.

D301 scheduling instructions are in accordance with the signal to drive, then all the way in front of a green light, the driver should be based on that D3115 has entered the Wenzhou South Station, the front of the interval, so normal high-speed driving. From Yongjia station to the site of the accident about 14 kilometers, D301 only ran for about 7 minutes, with an average speed of 120 kilometers per hour and a top speed of nearly 200 kilometers per hour.

The last technical barrier disappeared before the giant D301. To save the lives of two passengers, only the last possibility is left: The dispatch control room should be able to see the two vehicles that are approaching each other, and can also park by radio.

But why did the radio call not happen? At present, the problems occurring in the dispatching room are still under investigation. One analysis believes that in order to allow the D3115 to visually pass through the red band, the dispatcher will instruct the driver to close the signal system and then stop reporting the train position after the shutdown. The D3115 is in dispatch control. The room disappeared.

Nothing can stop the tragedy from happening. Starting from 20:25 on the 23rd, a series of plausible complex schedules actually put the two trains on the edge of the fatal cliff, and the failure of the signal equipment finally pushed the two cars down the cliff.

D301 came over. It apparently did not meet the "red light that must appear." At 20:31, D301 got on the bridge and the driver seemed to have braked. But apparently too late - D3115 is crawling at a slower speed of 20 kilometers per hour.

The eyewitness Shou Dashan watched as D30 ran into D3115 in front of him. “The train behind is like a horse. After the collision, ride & rsquo; to the front of the car, then a few cars turn over the bridge.”

According to the site investigation after the accident, after the two vehicles collided, the rear car D301 head climbed into the tail car 16 of the preceding car, and the 16th car was instantly collapsed and the passengers were mostly from this car. Then D301's first four cars followed D3115 and dropped off the viaduct from the left side of the bridge. For many people in the crushed 16th car and the 4th car that fell off the viaduct, this short time is the last moment in their lives. (Geng Jinping and Shu Mei also contributed)

Technical Causes of the "7.23" EMU Car Accident

The “Southern Weekend” reporter learned from the reliable insiders of the railway company that the technical cause of the “7.23” EMU special railway traffic accident has been initially ascertained.

The incentive was that the thunder and lightning interrupted the insurance of a railway ground equipment at the Yonglin line. It should be “guided to safety” after a failure. However, due to problems in the circuit design, the result was an upgrade of the fault, a circuit fault code, and a red code. Into the green code, the parking red light that should have been automatically turned on after the original failure became a traffic light.

It is claimed that the company responsible for the circuit design of the ground equipment at the accident section is the China Railway Signal Group, and the “pass number” is the predator in the field of railway signal.

According to the source, at present, all roads are urgently changing circuit design, and the Ministry of Railways estimates that the entire circuit can be modified within a day or two. However, the person concerned was concerned that due to the problems caused by the immature design, it was uncertain whether there were other design flaws besides the failure.

On July 28, a letter of apology was published on the website of the Beijing Communications Signal Research and Design Institute. Quantongtong is a company under the Tonghao Group and is responsible for the entire construction of the communication signal system integration project of the project.

In addition to design factors, scheduling should also be responsible. In the dispatch control room, the staff can see the two trains in the accident and could have passed the station's radio call to prevent accidents.

Shanghai Railway Bureau: Signal Device Design and Defects in Wenzhou South Railway Station

According to Xinhuanet reported on July 28th, An Lusheng, the director of the Shanghai Railway Bureau, said that according to the preliminary analysis of the situation, the “7.23” motor car accident was due to serious design flaws in the signal equipment of Wenzhou South Railway Station and it was damaged due to lightning strikes. After that, the signal that caused the zone signal that should have been displayed as red was incorrectly displayed as a green light.

An Lusheng said at the plenary session of the State Council’s “7.23” special railway accident investigation team at Wenzhou railway line in Wenzhou on the same day that there were design flaws in the signal equipment designed by a research and design institute in Beijing and put into operation on September 28, 2009. use.

When he analyzed the problems of the railway department, he said that after the lightning caused the signal device failure at Wenzhou South Railway Station, the electric watchman did not realize that the signal may be displayed incorrectly, and the sensitivity of safety awareness was not strong; the key personnel of the Wenzhou South Station on the new equipment The lack of understanding of the performance and the inability to effectively detect and dispose of equipment in a timely manner revealed that the education and training of employees in the railway sector was not in place.

An Lusheng also said that the incidents reflect the ineffectiveness of field operations, and that the on-duty personnel of Wenzhou South Railway Station did not handle the faults according to the relevant regulations and failed to effectively prevent accidents; the equipment quality, personnel quality, on-site control and other issues reflected in the accidents This shows that the security foundation of the railway sector is still relatively weak, and these problems reflect that the safety management of the railway sector is not in place.

It is worth noting that the list of personnel removed by the Party Committee of the Ministry of Railways announced on July 24 by Xinhua.com, in addition to Long Jing, director of the Shanghai Railway Bureau, and Li Jia, secretary of the Party Committee, included He Shengli, the deputy director of the Department of Public Works and Communications.

In addition, Xinhua News revealed that on the July 23rd morning meeting of the “7.23” Wenzhou-Shanjiang special railway accident investigation team, the director of the State Administration of Safety Supervision Luo Lin announced the list of accident investigation teams and expert groups. Among them, Luo Lin is the head of the investigation team, and the head of the expert group is held by an academician.

Related to this, Xinhua News reported on July 27th that the person in charge of the relevant department of the Supreme People's Procuratorate confirmed that after the establishment of the “7.23” special temperature rail accident investigation team on the Shuwen line, the Supreme People’s Procuratorate sent staff to Wenzhou. Participate in accident investigation work.