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Denguin english summary

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publié le 22 janvier 2019

At about 17:30 on 17 July 2014 in the Denguin municipality in the Pyrénées-Atlantiques department, regional express train No. 867285 travelling going towards Dax on the railway line connecting this town to Tarbes caught up with TGV high-speed train No. 8585 and collided with it at a speed of 95 km/h.
This TGV was travelling at 30 km/h in accordance with an “entry into an occupied section procedure” implemented following a malfunction of stop signal S 23 located between Pau and Artix on the straight section of kilometre post 225 of the relevant railway line. After passing this signal as on a “free track”, the impacting regional express train was travelling at 128 km/h and its driver was unable to avoid the collision despite applying emergency braking.

The direct cause of this accident was the fact that signal S 23 incorrectly showed a green light while the next section was still occupied by TGV No. 8585.
This dangerous malfunction was most certainly due to an unintentional “free track” command from the signal involved due to several electric wires having been stripped by rodents that entered the signal box mentioned above along the straight section of kilometre post 225.

Two factors contributed to this situation :

  • the design and construction of the signal box did not provide sufficient protection against the entry of rodents on the one hand and the fact that the cables were not easily visible due to the layout of the signal box. In addition, the fact that the different electrical circuits were not separated made it impossible to avoid possible contact between conductors that could lead to dangerous faults ;
  • during maintenance operations, the damage that could be caused by rodents to electrical cables in signal boxes was not taken sufficiently into account.

In view of these factors, BEA-TT sent two recommendations to SNCF Réseau concerning the following aspects :

  • the first recommendation concerned signal box design ;
  • the second recommendation was to improve prevention of risks due to the entry of rodents into these facilities during preventive and remedial maintenance operations.