The road between the Mont-Blanc Tunnel and Le Fayet (20 km) is a continuous gradient with a difference in elevation of about 700 m. Inertia forces the driver to constantly retard his vehicle by means of the different braking systems (service brake, engine brake, exhaust brake, drive shaft brake). This study was motivated by accidents involving lorries which were caused by a loss of effectiveness of overheating brakes. The aim was to identify the factors of risk and to suggest appropriate measures to reduce them. The results enabled us to identify four driving strategies. Two of these are hazardous because the driver applies the service brake too much thereby causing the brake to overheat. Two factors cause these hazardous strategies:​ the difficulties which inexperienced drivers have in implementing the necessary speed control skills (namely the selection of an appropriate gear ratio), and working conditions (for example loading delays and mechanical incidents), coping with which sometimes leads to risk taking amongst experienced drivers. A variety of recommendations have been made:​ guidance and information measures, recovery measures, professional training for driving on difficult routes.