Background
O Porriño is a municipality of 19740 people (as of 2018) in the far northwestern corner of Spain, located in the autonomous community of Galicia 11km/7mi southwest of Vigo and and 12.5km/8mi north of the Portuguese border near San Caetano (both measurements in linear distance).
O Porriño is passed four times a day by the Celta, an international regional train service provided in cooperation by the Renfe (Spanish national railway) and CP (Portuguese national railway) to connect Vigo in Spain with Porto in Portugal at a scheduled travel-time of 140 minutes for a linear distance of 122km/76mi. The four daily services (two per direction) are evenly split between a Portuguese and a Spanish train driver. The service is provided by means of diesel multiple units on a line equipped for both countries’ railway infrastructure.
The train involved
On the day of the accident the first southbound service (Celta 420) was provided by CP 592 056–6. The series 592 is a three-car diesel multiple unit in service with the Spanish Renfe, who temporarily gave 17 units to the Portuguese CP for the Celta-services. Introduced in 1981 the series 592 is mostly found in regional and commuter services, with only 4 units having been upfitted for long-distance services. Each 3-car unit consists of 2 motor cars and an unpowered middle car, measuring 70.21m/230ft in length at a weight of 130 metric tons empty. Each motor car holds two MAN inline-six turbodiesel engines with a total power-output of 840kW/1126hp, enough for a top speed of 120kph/75mph (with the long-distance version having received new engines for a top speed of 140kph/87mph). The configuration of the train involved in the accident offers 228 seats, but only 63 passengers and 2 crew members were on board at the time of the accident. The units loaned to the CP carry a special yellow-white-black livery with both railways’ logos.
The accident
On the 9th of September 2016 Celta 420 is departing Vigo’s Guixar-station at 9:02am local time. The train is under the command of a Portuguese driver while a Spanish conductor is in charge of checking the tickets of the 63 passengers. At 9:22am the train approaches O Porriño station under a 30kph/18.6mph speed limit as its path will divert it to the right into track 3 instead of continuing straight ahead into track 2. The data-logger will later show that the train is travelling at four times the speed limit, clocking 118kph/73mph as the driver acknowledges the entrance-signal for the station.
At 9:25am the train crosses the set of points diverting it into the right-hand track, bending the rails outward as inertia fights the tracks for control over the train’s path. The leading car finally derails 44m/144ft past the points, crossing another track and striking the track-side wall of a road overpass at 110kph/68mph. The driver’s cab is obliterated as the forward section of the leading car folds to the right, pushing the train back towards the tracks. The collision with the overpass and the resistance from the gravel ballast significantly slowed the train, a collision with a catenary support mast brings it to a stop largely aligned with the track next to the one it was meant to be on. The driver, conductor and two passengers are killed in the derailment, 47 people are listed as injured. All deaths and most injuries occurred in the leading car, due to the deformation as well as the most violent motion during the derailment while the rear two cars ended up almost undamaged.
Aftermath
First responders are at the site in minutes as the train had derailed just a few feet short of the station’s platform, right in the center of town. The local fire department stabilizes the leading car to keep it from falling over on its side while most passengers in the rear two cars manage to leave the train on their own. Arriving medical personnel set up a field hospital on the nearby platform to evaluate the survivors and treat those with minor injuries as ambulances take the more severely injured survivors to the surrounding hospitals. According to some sources one of the victims originally survived the derailment but was pronounced dead upon arrival at the hospital. With all survivors off the train and the leading car’s wreckage secured against falling over the responders went about cutting apart the leading car, recovering both the train’s data-logger and the victims in the forward section.
Due to the international character of the train involved several investigations were launched at once, with the infrastructure-company Adif, Renfe as the provider of the service and the federal railway accident investigation commission (CIAF) running separate investigations of varying depth. The site was cleared a few hours after the accident, hauling the train off to a maintenance facility and clearing the way for construction crews to repair the damage to the tracks and supporting infrastructure before the line was reopened 28 hours after the accident.
Adif’s investigation concluded first, placing sole blame on excessive speed but finding no fault with the tracks or signaling system, clearing them of responsibility. The signaling-system had worked properly, with recorded data showing that the driver had acknowledged all signals along the route, the last one mere seconds prior to the derailment, actual obeying of which would have had the train adhere to the speed limit and avoid the accident.
Renfe’s investigation agreed with the cause being soley excessive speed, pointing out that there was no sign of a pre-existing defect to be found as investigators examined the train. The investigation does point out that the collision with the overpass significantly worsened the outcome, explaining that merely derailing at high speed with a clear path ahead would have seen the train lose speed and eventually dig into the ground, likely putting an end to the derailment without claiming lives. Renfe’s investigation did admit that the train control system left something to desired, on the technical side. The train was equipped with the Portuguese Convel train control system for the Portuguese part of the trip as well as with the ASFA-system used in Spain. At the time of the accident the ASFA-system was set to what is called the analogue mode, in which it doesn’t ensure adherence to speed limits but merely informs the driver about upcoming signals, requiring them to be acknowledged by pressing a button to avoid an emergency stop being triggered. The exception is the passage of a red signal, which automatically triggers an emergency stop in any case. In 2005 ASFA had been upgraded to a digital setting, which allowed further functions including autonomously limiting a train’s speed as the system was integrated into the standardized European ETCS-system. However, at the time of the accident the digital mode was not in use on the involved train. As such, the system couldn’t do anything but assume the driver was aware of the speed limit and his own speed as he confirmed the instructions from the trackside signals.
Lastly, in March 2019 the CIAF presented their report on the accident. It states that the driver was most certainly aware of his excessive speed, as he consistently confirmed signals along the route, all but eliminating the theory that he became incapacitated. The report largely aligns with Renfe’s findings, explaining how the technically sufficient analoge ASFA-system was rendered incapable of avoiding the accident by the driver acknowledging the imposed speed limit while travelling at a speed several times that of the limit. An exact motive for that decision remains unclear. Had he gone through the signals without acknowledging them, even the last one right outside the station, an emergency stop would have been triggered, avoiding the accident or at least ensuring less severe consequences. The driver had 21 years of experience as a train driver and had always passed seminars with top grades. The CIAF does note that the train used to be sent on a straight path through O Porriño station, diverting it onto the side-track was highly unusual. This led to the main theory for why the driver ignored the speed limit being that he acted on habit more than on actual attention to his surroundings, believing he could go right through the station without any problem. To add insult to injury it was revealed that the train was only meant to be diverted off the straight path as Adif had wanted to see if the system worked correctly, having had problems with the set of points in question. There was no operational reason to divert the train, it could have passed straight through the station just like it had any other time.
In the end sole blame was placed on the driver, while Adif’s decision to use a regular passenger service to test the diversion-system was criticized but deemed insufficient to place fault. Whatever the reason for it is, a driver has to actually obey instructions given by the signals he passes, not just acknowledge them with a button and proceed to do whatever he feels is right. Another rumor was that the driver had been on the phone at the time of the accident, distracting him from his actual job, but according to the CIAF this could not be proven or disproven. It has to be noted that the CIAF had been criticized for insufficient investigations in the aftermath of the 2013 Derailment at Santiago de Compostela which claimed 80 lives, so one can suspect that they might have chosen to be satisfied with the explanation they had instead of digging deeper.
Since the accident ASFA digital has been expanded in use, but apparently still isn’t the sole mode used, leaving a risk of a repetition of the accident. The series 592 is in the process of being phased out, having reached 40 years of age. Several different trains take over the various services provided by the series 592, with the international Celta-service being set to be handled by the series 594, a license-built version of the Danish MF-series diesel multiple units which are significantly younger and more comfortable while also bringing an improvement in crash safety.
_______________________________________________________________
A kind reader has started posting the installments on reddit for me, I cannot interact with you there but I will read the feedback and corrections. I will link the post here as soon as I can. Please give it some love, I’m very thankful for the posts being published there.
