Abstract: The powered tracked vehicle is equipped with photocells (13, 45) which monitor its backward and forward movements and automatically modify their orientation according to whether the vehicle is travelling on the level or negotiating stairs or a slope. The inclinometer (25) that monitors the attitude of the chair is located in a protected inner part of the frame (3) and is connected to the chair itself by means of a hinged parallelogram (57, 59, 103, 105). The inclinometer is mounted on one of the sides of the hinged parallelogram via a pivoting support (61) which, by means of a sheathed cable (66, 65) and a feeler (67), detects whether the vehicle's front runner (70) is raised or lowered and transmits to the chair the advance backward tilt required when beginning to descend a flight of stairs. Other devices are also provided to make the vehicle as safe to operate as possible.