Following a 1999 accident in the Mont Blanc tunnel, measures were taken at the start of 2000 to improve safety in the tunnel. A strict speed limit, and a safe distance of between vehicles was imposed. The tunnel was equipped with the latest smoke and flame detectors, and a system of videocameras in the tunnel to detect the speed of traffic, as well as fire and smoke. Temperature sensors were installed at short distances throughout the tunnel, monitored from a central control post. Fire hydrants were installed every 130 m, fed from large water tanks. There are 11 safety points along the tunnel, equipped with telephones and loud speakers connected to the control room, with a separate ventilation duct to supply fresh air. These are separated from the main tunnel by two fire doors; the outer door closes automatically when the temperature in the tunnel reaches a certain level. Finally there is a ‘thermal gate’ system at each entrance to identify any overheating vehicles.