Dürrenast railway accident
Coordinates: 46 ° 44 ′ 40 " N , 7 ° 37 ′ 37" E ; CH1903: six hundred and fourteen thousand three hundred and ninety-six / 177 059
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In the railway accident at Dürrenast near Thun on May 17, 2006, a service train with non-functioning brakes hit stationary construction wagons on the open stretch . In order to avoid even greater damage, the dispatchers directed the service train onto a track that was closed due to construction work. Three employees on the train were killed.
Starting position
On the night of 16 to 17 May 2006, one was Bauzug the BLS in Blausee-Mitholz to replace a switch. At about 12:45 the construction train took five people - a locomotive engineer and a rail tractor leader of the BLS and three engineers from private construction companies - to Frutigen . Due to a braking problem on the second rearmost car of the service train, the journey to Frutigen was delayed by about two hours. The blocked brakes of the car could be released, but the affected vehicle had to be removed from the composition because of a flat spot together with the corresponding protective car . During this maneuver, the crane truck lined up at the Zugspitze was also attached to the rear of the train.
Compilation before adding the defective car
← Direction of travel Frutigen
|
BLS crane |
BLS Tm 99 |
Sersa protection car |
Sersa protection car |
Vanoli MFS |
Vanoli MFS |
Sersa AVES |
Sersa AVES + |
Tm 99 = diesel- powered rail tractor BLSTm 235 099-9, AVES = Sersa old material loading unit, MFS = material conveyor silo (ballast wagon)
Compilation of the composition after the defective car has been put into line
← Direction of travel Spiez
|
Tm 99 38 t |
Protection car ≈ 15 t |
MFS ≈ 90 t |
MFS ≈ 90 t |
AVES + ≈ 50 t |
Crane ≈ 15 t |
The composition had a total weight of approx. 300 t.
It was planned, the loaded gravel cars to Hondrich South at Wimmis into the siding to bring a gravel pit, there to unload the old ballast. One of the machinists stayed on the train, the other two could go home.
Course of the accident
The train left Frutigen at 3:01 a.m. When passing through Reichenbach , the engine driver reported to the dispatcher in Spiez that he was not having any braking effect. The engine driver asked to be able to drive straight ahead and not to be led into the siding of the gravel works. Because of the hustle and bustle and the noise in the driver's cab , communication via radio was difficult. The driving speed at this time was about 80 km / h.
The last radio contact was shortly before the Hondricht tunnel . An unimaginable stressful situation, accompanied by fear and despair, must have prevailed on the train. Apparently the engine driver failed to change the radio channel at the Hondrich tunnel . The dispatcher asked the drivers several times to call him on the mobile phone.
The dispatcher let the train drive to Spiez as requested and set shunting routes , which kept the main signals closed. She did not yet know the exact reason for the braking fault and hoped that the train protection would trigger an emergency brake. Under great time pressure, the dispatchers in Spiez were looking for various options where and how the service train could be stopped:
- A diversion in the direction of the Simmental was rejected because a construction site had been set up between Spiez and Wimmis and part of the rails had been removed. It was assumed that there were heavy construction machines there. The time to warn the construction workers would not have been enough. Driving over switches in Spiez train station, which are designed for a speed of 40 km / h, as well as over several unguarded level crossings was assessed as a high risk.
- A trip in Gwatt over distracting points was waived. In the event of a derailment, residential buildings would have been at risk, or the journey would have led over an unsecured road. The train had reached a speed of sometimes more than 100 km / h in Spiez.
- They wanted to avoid a trip to Thun train station because all of the high-speed tracks were occupied. There was a train from the Rolling Autobahn on track 1 . It was not known whether trucks were loaded with dangerous goods. The very high occupancy of Thun train station resulted from a personal accident the previous evening. A trip into the Gürbetal was out of the question because points for a speed of 40 km / h are also installed here and the remote control center responsible was not yet manned at this time. A trip to Stumpet tracks 209 or 210 would have endangered a road and the establishment of a gas supply .
- The dispatchers decided to direct the service train to a group of wagons on the opposite track at Dürrenast via a switch connection that could be driven at 60 km / h . They only had a few minutes to weigh only bad alternatives against each other. The train was supposed to be brought to a stop with relatively little damage due to a collision with two groups of site trailers about 500 meters apart. The dispatchers did not know that the first car was loaded with scrap .
The eleven workers who were involved in dismantling the abandoned Dürrenast stop ( km 1.4 from Thun) and building noise barriers (km 0.9) were able to get to safety in good time and were uninjured. The attempt to put two more obstacles on the track failed. On the one hand, the time was no longer available and, on the other hand, the train was expected on the unlocked track.
For some , the service train had reached a speed of around 105 km / h. At km 1,4 it bounced at a speed of 89 km / h first two braked cars. These were pushed with the escaped train to the group of wagons at km 0.9. There there was a collision with the construction vehicles standing there and the derailment of the rail tractor and several wagons. The impact was so severe that all three people were killed on the train involved in the accident.
Results of the accident investigation
The investigating authority found that the shut-off valves on the main air line between the rail tractor and the first wagon were closed. As a result, the attached wagons were unbraked, which explains the insufficient braking power of the train. The authorities assumed that the brake test was only carried out by one person. After the accident, it was no longer possible to determine who carried out the brake test required after the maneuver in Frutigen. Obviously problems arose during the performance of the brake test which were improperly rectified by manually triggering the car's brakes. The brake test was not repeated.
After the departure from Frutigen, the effectiveness of the air brake was checked. It is not known how fast the train drove when it left Frutigen station and at what speed the engine driver carried out the braking test. The diesel tractor was equipped with a remaining distance registration, which only saved the speed of the last 3900 meters to the scene of the accident. The technical equipment of the Tm 235 099 rail tractor did not allow the effective braking test to be carried out correctly. In addition to the compressed air brake, the tractor's braking equipment also included a wear-free electrical resistance brake , with the drive and brake being operated via a combined drive / brake switch on the radio remote control unit . Because a separate control of the compressed air brake was not possible, the effective brake test could not be carried out correctly.
Test drives as part of the accident investigation showed that up to a speed of 50 km / h, the train could only have been braked with the resistance brake of the rail tractor. If the effective braking test had been carried out as prescribed shortly after departure at around 30 km / h, the train could have been decelerated with the brakes of the rail tractor alone.
As part of the accident investigations, further findings came to light that were not the cause of the collision:
- The brake line between the second and third car was not coupled. It could not be proven whether the separation happened before the accident.
- The load changes of the loaded ballast wagons were in the empty position . The compressed air brake would have worked only weakly without the other defects.
- The Tm 235s were regularly used on the route as well as on workplaces. Speedometers with remaining distance registration are not permitted in the route service because the investigation of an incident after an accident is only possible to a limited extent.
The effect of the drag brake of the Tm 235 decreases sharply at speeds over 50 km / h. In the past, steep gradients such as the Lötschberg route were only allowed to be driven by locomotives with a powerful resistance or useful current brake .
literature
- Walter von Andrian: Fatal brake failure at BLS construction train . In: Swiss Railway Review . No. 7/2006 . Minirex, ISSN 1022-7113 , p. 330-332 .
Web links
- Ulrich Baumann, Joseph Zeder: Final report of the Accident Investigation Center for Railways and Ships on the impact of a service train on a stationary group of wagons on Wednesday, May 17, 2006 in Dürrenast / Thun. (PDF, 2.4 MB) UUS , April 20, 2007 .
- The ghost train from Spiez. (Video) SRF , September 7, 2019.