position for the deformation sensor in the interior of the side part on a side part reinforcing element namely a reinforcing pipe here side part 1 includes a door surface 2 and a recess 3 for the window area the a pillar area is shown as 4 and the b pillar area is identified as 5 the door threshold area on the bottom side of side part 1 i e a vehicle door here is labeled as 6 a sensor 47 in the form of a strain gauge sensor dms is arranged in sensor position 7 approximately opposite the center of door surface 2 on the reinforcing element in the interior of the door in the configuration according to fig1 sensor element 8 which senses the deformation of the reinforcing element is designed as a single strain gauge resistor sensor element 8 is designed to be sensitive to elongation and compression in the micrometer range and has a k factor of approximately 2 this means that the resistance of sensor element 8 changes by 2 with a 1 change in length of the strain gauge very precise deformation sensors i e force measurement sensors may be implemented by using strain gauges furthermore strain gauge sensors permit a single change in length of approximately 10 sensor elements 8 used in the diagram according to fig1 cover.