Background
Yilan is a municipality in northern Taiwan, located on the country’s eastern coast 57km/35.5km south-southeast of Taipei and 88.5km/55mi east of Hsinchu (both measurements in linear distance).
The municipality is crossed by the Yilan Line, a double-tracked electrified main line serving 27 stations on 94km/58mi of track along the north-east corner of the island. The line opened in 1924 while the country was under Japanese rule, became double-tracked in the 1980s and was electrified by 2003. Both freight trains and passenger services use the line, reaching scheduled speeds of up to 150kph/93mph. The line is constructed in “3ft 6in narrow gauge”, putting the rails 1067mm apart instead of the global standard of 1435mm.
The Train Involved
The Yilan Line is used by the Puyuma Express, an express passenger service introduced in 2013. The service uses the specifically developed Nippon Sharyo TEMU 2000-series, a tilting electric multiple unit (hence the name TEMU). The type was introduced as the service debuted 2013, with 19 train sets being constructed. Each train consists of two control cars and six middle cars, leading to a total length of 186.39m/552.5ft at an empty weight of 317 metric tons. The trains don’t have dedicated motor cars, instead spreading the propulsion system throughout the train similar to other modern EMUs. Each TEMU 2000 is split into two “propulsion units”, meaning a full eight-car train has a dual propulsion system. The top speed is listed at 150kph/93mph, but service sees no more than 130kph/81mph. Up to 372 passengers can ride on each train via a pre-travel reservation-only system, standing passengers are not allowed. The tilting technology, which is found on a few multiple units across the globe, leans the body of the train into corners by a few degrees, allowing higher corner-speeds without forcing the passengers to endure excessive centrifugal forces. This technology was included as Taiwan’s mountainous landscape allows barely any straight sections of rail line.
The Accident
The southbound Puyuma Express service is provided by TEMU 2000-set number 4 on the 21st of October 2018. The train is approaching Xinma station in Yilan by 4:45pm, running nearly at capacity with 366 passengers. The approach towards Xinma station from the north consists of one of the line’s few longer straight sections, followed by a wide left turn before a sharper (300m/980ft radius) right turn marks the beginning of Xinma station, with the station’s main platform beginning within the curve. Trains intending to pass through the station, like the Puyuma Express, are limited to 75mph/46.6mph. The Puyuma Express reaches the right hand turn at 4:49pm, travelling at 141kph/87.6mph. A number of survivors later recalled an emergency stop being triggered as the train navigated the left hand turn, while others would report no such event. Either way, even if the brakes were applied it’s too late to avoid the impending disaster.
The centrifugal forces immediately overcome the leading car of the Puyuma Express as it enters the sharp right hand curve into Xinma station, pulling it almost straight off the tracks. The leading car separates from the rest of the train and actually somewhat follows the rail line (be it on the oncoming track) as it falls over, while the now headless train derails behind it, heading straight off the tracks and into the adjacent undergrowth. The derailment of the second car destroys the tracks, a bent up rail pierces car six like a lance as it turns sideways on its way off the tracks. The third through 7th car fold up in a W-shape as the resistance from the slowing car in front slows each following car down unevenly. Only the rear cab car remains on the tracks throughout the derailment. Several of the train cars fall over as their wheels dig into the ground once they are off the tracks, but limited collisions between them allow most of the train cars to largely maintain their survival space. Yet still, 18 people die in the derailment and 233 are injured, with most victims being found in the leading car.
Aftermath
People waiting at the station are the first outsiders to come to the survivors’ rescue, a few minutes before the first emergency responders reach the wreckage. Almost 400 professional responders, including 100 soldiers, become involved in the rescue operation. The driver, who was among the survivors, is detained upon being released from the hospital and gets interrogated by both the police and the investigation. The investigators were puzzled how the accident could have happened on the modern rail line with a 5 years old train, which had seen an extensive inspection/overhaul just a year prior. The two together should have meant that a train couldn’t just go too fast, much less by such a wide margin. Among the systems involved was the train’s Automatic Train Protection system (ATP), which constantly monitors the train’s speed and will trigger an automatic stop if the local speed limit is breached.
The investigation finds out that the driver had reported problem’s with the train’s main air compressor, which supplies the brakes, doors and toilets, earlier in the day, claiming that it had only been working intermittently, reducing brake-performance. The fault had shown up first at 2:50pm when the train departed from Shulin station, with the dispatch center ordering the driver to disregard the fault and continue on his way as even a full failure of the compressor would still leave sufficient braking-power for a safe operation. The train subsequently collected 4 minutes of delay by the time it passed through Shuangxi station, approximately 90 minutes up the line from where the accident later occurred. An attempt to reset the train’s systems following the passage through that station failed, at which point the train’s own safety-systems temporarily cut power as air pressure fell below a programmed minimum value. The system, which works via the ATP’s brake application ability, kicked in a full ten times, the final interference being recorded by 4:17pm. By that point the train had collected a total delay of 14 minutes due to being unable to uphold a steady speed. The driver reacted by disabling the ATP-system at that point before proceeding on his way with the system’s brake applications no longer interfering.
Recordings show that the train performed an unscheduled stop at Yilan station (named after the city of Yilan, located within the municipality), with the driver unsuccessfully attempting to solve the problem. He then received instruction to proceed to Hualien station, approximately 2 hours beyond the site of the accident, where the train set would be swapped out. Departing a station with the ATP-system disabled should have automatically triggered an alarm at the dispatch center, which didn’t happen. The train reaches 140kph/87mph at 4:46pm, 2 minutes after passing through Luodong station. The driver is engaged in a conversation with the dispatch center, still aiming to figure out how to handle the compressor failure, likely intending to avoid further delays, not to mention a replacement of the whole train set. The conversation ends as the train derails outside Xinma station.
The investigation sees this chain of events as proof of fault by the driver, who departed without ATP enabled, possibly in an attempt to catch up some of the delay, and then forgot about the upcoming turn, leading to his train entering the curve at nearly twice the speed limit.
A probe into the ATP surveillance system shows that none of the TEMU 2000-sets had their system connected, meaning that the dispatch center would never know if their ATPs were turned off on departure from a station. Nippon Sharyo released a statement on November 1st explaining that the construction-instructions they received included the ATP-system being disconnected from the remote maintenance system (the component reporting to the dispatch center) and that they were not allowed to perform electric work in Taiwan. They had thus delivered the trains with the system disconnected, expecting Taiwan Railways Administration’s (TRA) own maintenance crews to connect the wires and ensure proper operation of the system. However, recordings showed that the system was not part of the pre-service checks. This explained why the system was found to have been left disconnected on all TEMU 2000-sets, as it had been delivered as such and the railway company had failed to connect the wires.
Adding insult to injury was the fact that a driver told the investigation that the type had had repeated issues with the air compressors and/or other parts of the onboard diagnosis system, sometimes confusing drivers and leading to distrust towards the system’s reliability and honesty. TRA had also not yet acquired a compressor testing machine compatible with the TEMU-2000 by the time of the accident. TRA denied the claims by the driver, but did so without providing reliable proof. One thing they couldn’t deny were recordings of several incidents where the compressor on set 4 (the one involved in the accident) overheated, leading to automatic shutoffs the way they had been experienced ahead of the accident as air pressure dropped below the threshold.
The investigation concluded in June 2019, with a press release by the municipality’s prosecutor’s office. It was announced that the accident’s cause was negligent driving by the driver, who departed without ATP engaged and failed to observe the speed limit in absence of the system. An initial claim that he had “secretly” disabled the system was refuted by radio traffic recordings which had the driver tell dispatch that he had disabled ATP so it would stop interfering with the train’s driving. It is assumed that low trust in the system’s reliability and the inability to clear the fault had outweighed the estimated chance of an actually defective compressor, leading to the driver prioritizing timely service which was only possible with the ATP-system “isolated” from the train. He was subsequently indicted on several counts of negligent homicide.
The investigation decided that the faulty compressor had not been a contributing factor by itself, as the train could have functioned, including decelerating, sufficiently despite the issues at hand. The disconnected ATP surveillance system led to the former Deputy Director of TRA’s fleet management along with the Chief of their central dispatch center being indicted as well, as it was deemed to be a gross oversight to not have the system operational even years after the type’s introduction.
The Taiwanese government expressed dissatisfaction with the investigation and its outcome, leading to the Aviation Safety Council (ASC), which previously only dealt with aviation-related incidents, being converted into the newly established Taiwan Transportation Safety Board (TTSB) which would now also cover maritime, highway and rail traffic incidents. The investigation into the Yilan derailment had been conducted by a temporary group assembled for this particular investigation rather than a permanent institution.
Legal proceedings following the indictments finished up in fall 2021, with the driver being sentenced to 4.5 years in prison for negligent homicide. The other two indicted individuals were found to be of insufficient criminal guilt to justify a sentence. The court also noted that the driver had only been working on the line as a substitute and had “low, if any, familiarity” with the route, so he might not have known about the specifics of the upcoming turns. This, however, was placed in contrast to his choice of proceeding without ATP. It was thus not seen as an excuse of his failure to slow down, with the court instead using the chance to criticize TRA’s excessively thin staffing which had forced them to place an inexperienced driver on the route.
TRA also attempted to sue the train’s manufacturer, citing the repeated issues with the compressor system, demanding 610 million Taiwanese Dollars (177.2 Million Euros/193.2 Million USD). The case went to court, where TRA lost the case.
The TRA proceeded to fit the remaining TEMU 2000-sets with a speed limiter which, if ATP is disabled, automatically limits the train’s top speed to 60kph/37mph in order to avoid derailments due to disabled ATP-systems allowing excessive speed in the future. The same system was also fitted with priority to Taroko-type trains before other train types were considered. The TRA announced in March 2023 that 400 trains had been fitted with the limiter. The trainset involved in the accident was deemed to be beyond saving and was scrapped once the TTSB decided not to open a new investigation.
The derailment at Yilan was far from the first time a train derailed in a sharp curve due to excessive speed, and as disappointing a note to end on it may be, it probably won’t have been the last time. The TEMU 2000 is a modern train, and it had modern safety-measures in place. It’s the human factor that remains a possible source of issues. The driver of the train which derailed at Yilan had no ill intentions in disabling ATP, quite the opposite, arguably. His aim was to catch up the delay and provide a good service.
On modern trains the driver is trusted to maintain proper speed limits, while train control systems like ATP are there as a “backup” so that wrongdoing by the driver alone can’t lead to an accident. At the same time, the driver is there so a malfunctioning ATP-system can’t lead to an accident. Yilan was the unfortunate situation of both these systems failing, with one being turned off and the other, in simplified terms, not functioning correctly. And there wasn’t a third layer of safety-measures in place. The added speed limiter for non-ATP operation is an additional safety-feature that will reduce the risk in the future, with the improved training promised by the TRA regarding safety-systems hopefully reducing the risk on the human side as well.
Video
The Daily Telegraph, a newspaper from England, published CCTV footage online which shows the train derail as it enters the station, along with footage of the wreckage. Be aware that the video can be distressing to some people:
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