The objective of this paper is to examine automobile bumper systems in aligned low-speed impacts and provide data which correlate compression of bumper systems with the vehicle impact severity.A significant number of automobile collisions involve bumper-to-bumper contact at speeds which produce little or no permanent vehicle damage. Contemporary bumper systems predominantly consist of a fascia and impact beam, which span the vehicle width, and some form of impact absorber. A common impact absorber is the shock-absorber-type isolator. Foam cores, deformable steel struts, rubber shear blocks and leaf springs also exist.Data from 58 vehicle-to-barrier and 136 vehicle-to-vehicle aligned impacts are presented. Impact duration, speed change, isolator compression, and coefficient of restitution results are presented and discussed. Static and dynamic compression tests on several isolators have been carried out. A number of isolators were sectioned to develop structure-property relationships.Speed change as a descriptor of impact severity in these collisions is proposed. Its relevance to injury potential is discussed and the data for estimating speed change based on the post-collision condition of the isolators is presented.It is concluded that bumper systems on passenger cars available in North America, though built to meet specific government standards, have impact characteristics that vary among vehicles. It is also shown that certain vehicles can sustain significant front or rear impacts without sustaining damage.