a bumper system adapted to be mounted on a vehicle includes an elongated , inflatable bag fastened by its two ends and by opposed longitudinal ribs to and within a shell having a concave front and a forward facing impact support beam behind the shell spacedly attached to the shell . a rotatable impact energy transfer element is connected to the shell so that it is adjacent to the circumference of a wheel of the vehicle , and the axis of rotation of the transfer element is parallel with the axis of rotation of the wheel of the vehicle .