Abstract: Protection devices in motor vehicles typically have a movable element, for example a roll bar (1) or a flap, which, in the initial state, is fixed in its position by a releasable holding device. In the event of a hazard, the movable element can be released under sensor control by a common pyrotechnic actuator (11) and can be deployed with the protection being activated. The protection device also has a means (8, 9) for locking the deployed, movable element. A driving pressure chamber (12, 15), which is fixed on the bodywork and in which a driving piston (2 with 13, 16) connected to the movable element is accommodated in a guided manner, is connected downstream of the pyrotechnic actuator (11).