An extendable and retractable bumper (E/R bumper) is presented in this paper. The E/R bumper is intended to automatically extend in situations in which there is a high risk of frontal impact to prepare the vehicle for crash and retract when the risk subsides. A functional demonstration vehicle and two experimental vehicles were built with the E/R bumper. Analytical and nonlinear finite element models were used to aid in the design of these vehicles, and to predict their crash performance in full, offset and oblique impact tests. While the functional demonstration vehicle was used to study its control and operation sequences, the experimental vehicles were crashed in a 56kph rigid barrier impact test and a 64kph 40% Offset Deformable Barrier impact test. These crash tests, together with nonlinear finite element analysis, showed that the additional crush space realized by extending the bumper could reduce the severity of the crash pulse and the amount of structural intrusion to the vehicle compartment.