s formed portion 18a in the embodiment of fig5 and 6 the sensor 16 is placed above the end 12a of the tube the sensor 39 s abutment stud 16a projects somewhat above the end of the tube and can be operated by an end piece 18 which as in the foregoing embodiment is pivotally connected with the end of the tube via an s formed part 18a due to the fact that the arrangement of the end piece 18 is such that it has a significant extension in a plane extending crosswise and to a greater extent perpendicular with respect to the sensor 39 s abutment stud 16a a widened field of operation is obtained fig7 shows a schematic view of one example of how the vehicle 39 s door 21 can be formed in order to transfer the deformation forces from a vehicle 22 coming in from the side through the door via a cellular plastic block 23 to the end piece 18 and the sensors 16 mounted in the seat 39 s stable tube frame 12 the collision force from the colliding vehicle is lead quickly through the door via the stiff cellular plastic block 23 and the door panel to the sensor in the seat frame the door can alternatively be equipped with an inner plate or sheet structure 24 as shown in fig8 the plate structure comprises longitudinal and lateral plates 24a and 24b respectively in the door interior said plates bridging the space between the strengthening member 25 in the door and a.