Compressible shock absorber (100), characterized in that it includes at least one pair of shock absorbing elements (110) co-axial and telescopic reciprocally sliding along a longitudinal sliding axis (X); said shock absorbing elements (110) co-axially include a cavity (115) and include therein a compressible air volume during their axial sliding reciprocal between a first position of maximum axial extension and a second position of lower axial extension; said at least one pair of shock absorbing elements (110) includes air extractors (140) susceptible of allowing an extraction of the air from said internal volume progressive with the reduction of the axial extension following the impact of a vehicle against said shock absorber.