Unsafe practices of truck drivers on long grades: the case of the expressway in the Mont-Blanc-Le Fayet tunnel

The road tunnel of Mont-Blanc/Le Fayet (20 km) is a continuous grade with a difference in elevation of about 700 m. Inertia forces the driver constantly to retard his vehicle by means of the different braking systems (service brake, engine brake, exhaust brake, retarder). Accidents involving trucks arising from a loss of efficiency due to overheating brakes motivated this study. The aim was to identify the factors of hazard and to suggest appropriate measures to reduce them. The results allowed us to identify four driving strategies. Two of them are risky because the driver puts on the service brake too often which produces brake overheating. Two factors cause these risky strategies: difficulties encountered by inexperienced drivers who lack the required know-how to regulate speed (namely the choice of an appropriate gearbox ratio); working conditions (loading delay, mechanical incidents ...) which sometimes lead the experienced ones to take risks. Different recommendations have been suggested: guidance and information measures, recovery measures, professional training for driving difficult routes.