Eerste hypothese over treinramp Santiago de Compostela

Ik had een email interview met Associated Press. Nieuw voor mij. Ik dacht hier maar even te delen wat ik voor hen toch al intypte.

Q’s by AP

  1. – What does the blackbox of the crashed train record?
  2. – What will the safety research focus on?
  3. – What is the reason for the failure in your opinion?

A’s by WV

  1. What exactly the blackbox of this train type records, I don’t now. In general, they record the status of key train control systems, (like breaking, traction, signals (GSM-R or track) etc), sensors (temperature, position, speed etc) and communication.
  2. In general, safety research focuses on a reconstruction of the trains last trip and history (like maintenance). While currently there are a lot of hypotheses, safety researchers generally start from scratch to allow for the absorbtion of all lessons to be drawn.
  3. One of the current key hypotheses is that the handover between the ECTS (the train control module of the wider ERTMS, the European standard for rail traffic management) and ASFA (one of the Spanish train control system) went wrong. There seems to be a sluice of 4 kilometers (from kilometer sign 80 to 84) where that handover should take place. ASFA should take over from ERTMS for Santiago inbound trains in that sluice to allow them to come to a halt at the station at kilometer sign 88. That handover seems to have failed to slow the train down.
    The hypothesis is that design constrains for ASFA¹ are such that it does not register speeds of 180kph as too high. For a homologous system that would work fine. A train traveling under only ASFA would never reach that speed without the system intervening by breaking. On the interface between two systems (with ERTMS here allowing trains to travel 200kph) that could be problematic: the train could enter from the ETCS part at 200kph into the ASFA part. The reason it could have not surfaced here until now is the fact that for all drivers it is obvious that they should decelerate to 80kph when entering Santiago. So, the key role of the automatic train protection could have failed here due to the discrepancy in design constraints of both systems, the failure to spot that during the design of the sluice and the failure of the drivers to reduce the speed. Remember, train driver expect to be able to rely on the automatic train protection.
¹ Standard ASFA does not seem to communicate maximum current speeds to the train. This would incur the train side control system could also not correct for speeding, except for a fixed maximum speed, built hard into the trains control system. A more advanced version of ASFA TBS does communicate a current maximum speed and allows the train to intervene when that speed is passed. It is not clear which version is present in vehicle and track in Santiago.
By the way, Dutch ATB does communicate maximum current speeds to the train through pulses in the tracks. In addition, Dutch trains are slowed down when the trains moves faster than the maximum speed set at that particular moment.