Toulouse english summary

At 18:33 on 18 June 2013 on line A of the automatic rubber-wheeled Toulouse underground station, following a thunderstorm, train 18 travelling at 10-15 km/h towards the “Balma-Gramont” terminus collided with stationary train 39 at "Bagatelle" station, causing minor injuries to 3 people.
Train 18 was applying normal service braking in advance in order to stop before the beginning of the section occupied by train 39. As it was not decelerating sufficiently, its automatic systems triggered emergency braking. It was then in the tunnel on a section of the track with a 7% gradient. Its wheels locked and it slid about 170 metres.
Train 39, for its part, had been stationary for one minute and 36 seconds awaiting an order from the central control point to set off after having been unable to stop correctly in the station, also due to track adhesion problems.

The direct cause of the collision was insufficient traction of the train tires on the wet rails. Three factors contributed to this accident :

• poor drainage of water present on the tracks, scoring of the tracks in an unfavorable direction and machining faults ;
• polishing of the rails by the repeated passage of trains, reducing their roughness ;
• under-estimation of the consequences of wheel locking on train stopping distances during initial safety studies.

This analysis led BEA-TT to make four recommendations and four calls for action on the following matters :

• improvement of drainage on the rails ;
• timely restoration and maintenance of adhesion on the rails.