Background
Obereggendorf is a part of the municipality of Eggendorf (population in 2023: 5084 people), located in the far east of Austria 38km/24mi south of Vienna and 20km/13mi northwest of the Austrian/Hungarian border at Schattendorf /Sopron (both measurements in linear distance).
The town lies on the Pottendorf Line (Pottendorfer Linie), a 51km/32mi electrified and mostly double-tracked main line connecting Vienna with Vienna-Neustadt (a different and geographically separate city, somewhat confusingly). Opening in sections between 1871 and 1875 on a slightly different routing the line’s original purpose was to help improve the connection of Vienna with the “Transleithania”-area of the then-existing Austro-Hungarian empire. Nowadays the line sees mostly freight services and regional passenger trains at speeds of up to 160kph/99mph.
The Trains Involved
An international freight train was travelling northeast on the rail line on the day of the accident, consisting of 18 empty four-axle “Zacens”-type tank cars pulled by an ER20 belonging to RTS (Rail Transport Services, a private Austrian rail service provider). The ER20 is a four-axle multipurpose diesel locomotive made by Siemens under the “Eurorunner”-name, introduced in 2002. Each ER20 measures 19.27m/63ft in length at a weight of 80 metric tons and can reach 140kph/87mph thanks to a 1600kW/2145hp V16 diesel engine. RTS had a fleet of four ER20 at the time of the accident, it’s not known which one suffered the accident. The company lists them as the Series 2016, the same number ÖBB (Austrian national railway) gave the type.
The report lists a total train length of 312m/1024ft at a weight of 552 metric tons, with a scheduled top speed of 100kph/62mph. The train was staffed by a licensed driver along with a trainee train driver, with the licensed driver being in control at the time of the accident.
The ÖBB had conducted maintenance work on the area north of Obereggendorf ahead of the accident, using an SKL track geometry car. Track geometry cars are generally specialized rail cars which have various equipment onboard to measure the position, curvature, and smoothness of the rails along with their alignment with each other in order to discover faulty spots early without obstructing regular rail traffic.
The vehicle used at Obereggendorf was the EM-SAT 120, a four-axle motorized track geometry car measuring 16.14m/53 in length at a weight of 49.7 metric tons, capable of reaching 120kph/74.5mph. It was staffed by a crew leader, a driver, an engineer and two technicians.
The Accident
EM-SAT 120 had spent the evening of the 27th of March 2013 conducting track measurements on the northbound track of the Pottendorf Line, moving southbound. It pulls into Obereggendorf station at approximately 11:30pm, stopping on Track 1 (which is on the northbound side of the station) to let a freight train pass before it can continue on. The EM-SAT 120 stops just north of the platforms, at the (east-west) level of the main signal box. The crew leader steps off at 11:35pm, heading to the main signal box to coordinate further operations. This left 4 people (the driver, an engineer and two technicians) in the vehicle.
The rail line around Obereggendorf had no track occupancy detection system, so the track north of the station is cleared after the maintenance worker reached the signal box, where he also informs the dispatcher of the maintenance vehicle’s position. With the rail line north of Obereggendorf station cleared the signal box crew permits the approaching northbound freight train to pass through the station at its scheduled top speed of 100kph/62mph, turning the station’s southern entrance-signals green at approximately 11:45pm.
The freight train is driven by a licensed train driver at that time, with a trainee driver looking on and learning the route. The freight train enters the station at 11:47pm, just before, at a distance of 150m/492ft, the driver spots the headlights of the EM-SAT 120 in the distance. The driver triggers an emergency stop and manages to yell at his trainee to get on the ground before, at 11:48pm, the freight train plows into the stopped maintenance vehicle at almost full speed. The data-logger aboard EM-SAT 120, which was left powered up as the crew expected to soon proceed, registers an instant acceleration to 80kph/50mph as the vehicle is shoved back 350m/1148ft. Two men aboard the maintenance vehicle are killed in the collision, the other two along with the trainee driver on the freight train are severely injured. The freight train’s driver survives too, suffering minor injuries.
Aftermath
The conversation between the signal box worker and the head of the maintenance crew is interrupted by a deafening crash, looking outside they find the maintenance vehicle missing, replaced with a row of tank cars. It takes the group a few minutes to figure out what occurred, realizing that the freight train had been directed into an occupied track and disaster had struck. Almost 100 responders fill the site within a few minutes of the first call to emergency services being made, rushing the survivors to hospital and recovering the victims.
The police announces that they suspect human error to be the cause of the accident within 24 hours of the accident, as both trains were in fully operational condition. The bigger question is who exactly did what wrong to have the trains end up on the same track. The dispatcher in charge is no help to the investigation, not by choice but because he suffers from such severe shock that he’s admitted to a psychiatric facility the night of the accident, unfit to be interviewed by the investigation.
Investigators note heavy deformation of the freight train’s locomotive, although survival space was barely if at all compromised, while the maintenance vehicle shows very minor deformation beyond the testing-rig being torn from its mounts and partially forced into the driver’s cab. This means that any forces the freight train didn’t absorb were transmitted to the occupants of the maintenance vehicle. And it doesn’t take much knowledge to know that the collision must have been violent, instantly bringing the 49.7 metric ton vehicle to 80kph/50mph. The resistance from the collision and the maintenance vehicle being dragged along cut down the braking-distance of the freight train by 29%, bringing it from a calculated 571m/1873 to 410m/1345ft.
The biggest question left to the investigation is how the signaling system didn’t stop the freight train from approaching the occupied track at the station, but it’s also the easiest to explain. In short, the signaling-system didn’t know that the EM-SAT 120 was there. The train had been used to measure the northbound track while it itself was moving southbound, meaning it was running in the “oncoming” track. This was accommodated not by the usual process of a train requiring the “wrong” track (which is done during construction work, for example), but via a special exemption process. The EM-SAT 120 was treated similar to a shunting operation, moving independent of and undetectable by the signals. This independence is actually desired when actually shunting trains, as you don’t want the signal to auto-stop your train when you’re trying to assemble a train at the station.
The Pottendorf Line also wasn’t equipped with a track occupancy system, meaning the signaling system couldn’t track a train’s position in between signals either. It was down to the signal box crew to keep track of the EM-SAT 120 and route other trains around it or it around other trains. They had to keep in mind that they had directed it into Track 1 for parking and subsequently would have had to direct the oncoming freight train around it, since the signaling system wouldn’t prohibit the southern entrance-signal from being turned green.
Official guidelines dictate that the dispatcher has to ensure an unoccupied track ahead of permitting a train’s entrance into the station, either by looking out the window or, if necessary, by walking outside and checking the section in question up close. Obviously, this wasn’t done the night of the accident, or else the parked EM-SAT 120 would have been discovered.
Furthermore, the process the maintenance-vehicle was accommodated under required physical occupancy-locks to be attached to the signal-controls in the signal box if any vehicle was parked on a main track (those running directly through a station without separating from/merging with other tracks) for more than 10 minutes , preventing the signal from being set to green. This also wasn’t done.
The investigation adds a side-note of sorts in the report, explaining that the signal box crew at Obereggendorf station had also overstepped their boundaries when it came to the arrangement for the EM-SAT 120’s use, failing to sufficiently coordinating with the neighboring signal boxes. They had run the EM-SAT 120 not as a standard shunting operation but as a “Technical Work Operation” (“Technischer Arbeitseinsatz”, TAE), the rules for which required them to completely lock down the track the EM-SAT 120 was on with a fixed start- and end-point rather than going section-by-section and “improvising” each time they received information from the maintenance crew on their position. Adherence to those rules would have seen the northbound track north of the station as well as Track 1 within the station set to “occupied” as soon as the maintenance vehicle departed the next station to the north, preventing the freight train from being allowed to enter the occupied track at the station.
In summary, the cause of the accident lies mostly on a human level as the because the EM-SAT 120 was allowed to enter the station under unfit circumstances, with the signal box crew mixing different procedures which led to them adhering to the rules of neither. They also failed to attach occupancy-markers to the signal box controls, allowing the freight train to be permitted entrance to the same track from the south once the dispatcher forgot about the position of the parked maintenance vehicle. All of this could have been prevented with a track occupancy detection system, which would automatically block any section of track a train is running or parked on from being used as the path for another train. Such a system would have prevented the entrance-signal at the southern end of the station from being turned green regardless of the signal box crew’s failure to keep track of the EM-SAT 120.
Adding insult to injury was the discovery that this wasn’t the first accident in the area that could have been prevented by a track occupancy detection system. A different dispatcher had failed to spot a parked freight train at the same location in 2007, clearing the track for an incoming train intending to pass through. That train, too, ended up colliding with the parked train.
The dispatcher in charge of operations the night of the accident was eventually put on trial, being charged with several cases of negligent manslaughter and several cases of negligent cause of bodily injury in an especially severe case in April 2013. He admitted to having made a terrible mistake the cause of which he couldn’t explain. He was eventually sentenced to six months of probation along with an undisclosed fine in July 2014, with the court arguing that partial (but not legally sufficient) fault lay with the freight train driver who theoretically should have seen the EM-SAT 120 at a distance of up to 300m/984ft instead of the 150m/492ft he was away from it when he triggered the emergency stop, reducing impact forces. It was also taken into consideration that the dispatcher was suffering from the mental consequences of the accident so much that he had been unable to return to work. Several demands for damages, mainly a 1.5 Million Euro/1.6 Million USD claim by RTS, were rejected, with the court directing those claiming damages to civil action.
The ÖBB announced that they were in the process of improving the training of their signal box crews, with special focus on safety and unusual operations, and had also begun equipping several train stations with track occupancy detection systems. By the time the report was published in June 2014 they were working on the first “batch” of 50 stations. One is left to hope that, after two accidents, the improved training and introduction of the backup safety system will prevent a third from occurring from the same cause in the same place.
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