the vehicle occupant 10 as shown in fig2 the protective effect achieved with this design of the vehicle seat will now be explained in more detail as can be seen from fig1 in a normal sitting position a distance x which can be of considerable magnitude remains between the head of the vehicle occupant and the surface of the supporting casing 18 facing it furthermore a distance which in fig1 is referenced as y remains between the shoulders of the vehicle occupant and the back rest in the event of a rear end impact the gas generator 24 is activated by a controller unit according to predefined actuation criteria the gas bag 20 is inflated and escapes through the window of the supporting casing 18 tearing open the cover 22 the vehicle occupant 10 is pressed against the back rest 14 by his mass inertia whereby distance y must be overcome and distance x also becomes smaller before a pivotal movement of the head of the vehicle occupant can occur backwards in relation to the upper body the gas bag 20 is fully inflated and forms a support area which makes contact with the rear side of the head and which supports the head on the opposite side the supporting forces are absorbed by the supporting casing 18 as can be seen.