Abstract: The bumper of a vehicle is secured to the vehicle chassis by shock absorbers having each a cylinder attached to the vehicle chassis and a hollow piston assembly attached to the bumper. Liquid in the cylinder communicates with liquid in the piston assembly through a throttling passage in the piston, and a compressed gas cushion acting on the liquid in the piston assembly biases the assembly outward of the cylinder cavity against an abutment. The initial gas pressure and dimensions of the shock absorber are so selected that the total energy absorbed by the shock absorber while the piston assembly is pushed from its normal to its innermost position by the greatest impact energy capable of being totally absorbed is consumed to at least 20% by reversible compression of the gas cushion.