At least one drive machine (29) of the drive unit is mounted as an underfloor motor in the centre part (1) of the frame whic divided by longitudinal and transverse supports (14-22) in ladder like structure into lower areas (23-28) which house rigid constituent parts (29) of the drive unit and further rigid operating devices (31-34). The dimensions of the areas conform at lea in the transverse direction of the vehicle to the dimensions of the devices which are contained therein. Deformation members (35) are arranged between the cross supports on one side and the devices housed by the lower areas on t other. The width of the centre frame area corresponds to the width of the vehicle
