Abstract: An improved safety apparatus (10) is used in association with a belt (16) which restrains movement of an occupant of a vehicle. The belt (16) is taken up by and paid out from a retractor assembly (22). Upon the occurrence of vehicle deceleration greater than a predetermined deceleration, a solenoid assembly (132) operates a clamp assembly (28) to grip the belt (16) and prevent paying out of the belt. In one embodiment of the invention, the retractor assembly (22) includes a sensor assembly (54) which operates a retainer assembly (56) to prevent withdrawal of the belt from the retractor assembly when the deceleration of the vehicle is in excess of a predetermined deceleration. The sensor assembly (54) is mounted on a movable carriage (32) in the retractor assembly (22). Although the clamp assembly (28) and the retractor assembly (22) may be used in many different locations in a vehicle, they are advantageously located on the back (24) of a vehicle seat (12).