Saint-Germain-en-Laye english summary

At 06:12 on 9 December 2014 near Achères-Grand-Cormier station in the municipality of Saint-Germain-en-Laye in Yvelines, a suburban RER A train travelling on the 2bis line going towards Paris passed switch points 116 at 87 km/h where the speed limit is 30 km/h and was diverted to the sidings without the signals giving any notification. Fortunately the train did not derail and did not collide with any other rolling stock in the sidings. There were no casualties.

The direct cause of the incident was a wiring fault in the four electric control system cables for switch points 116 which occurred in the course of works to replace a signal cable with 28 pairs of conductors connecting the service room of signal post A to a signal box near these switch points. On conclusion of these works, the position of the switch points on the ground was reversed in relation to its control system and controls at the A signal post at Achères.
This wiring fault resulted :

  • on the one hand in a reversal of the terminals in the technical diagram describing the available cable ends in the signal box mentioned above, probably from when the facility was first installed. These wiring replacement works were carried out according to this inaccurate diagram and the error was neither detected during their preparation nor in the course of technical checks and tests ;
  • in addition, from the fact that the numerous provisions regulating works of this kind were not sufficiently familiar to the inexperienced works assistant of the “SES Mantes/Achères” production unit, who managed the work on his own and was never supervised, particularly due to the fact that no quality control process is implemented for this kind of work. Two instances of non-compliance with the requirements set out in SNCF specifications should therefore be noted :
    • In the documents he drafted for the wiring operations and technical checks, he based his work on one single type of diagram concerning this cable, neither using nor sending the other diagrams that would have made it possible to detect the reversal of the terminals mentioned above by cross checking ;
    • in the test program he prepared, he merely ensured a match between the commands and the controls obtained without checking the actual positions of the switch points on location, which would have made it possible to detect the functional anomaly.

Analysis of this incident resulted in BEA-TT sending SNCF Réseau four recommendations to improve :

  • the quality of training and supervision of young inexperienced agents who manage maintenance and works on signalling installations ;
  • the legibility of SNCF specifications for work on safety installations ;
  • the quality of the compliant diagrams of the safety installations ;
  • the quality of test programs for small-scale works on safety installations.

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