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There are many bumper-to-bumper automobile collisions in which a vehicle occupant claims injury but where there is little or no outward damage to the vehicles. On vehicles equipped with shock-absorber-type bumper isolators, the only “damage” often consists of compression marks left on the isolator piston tube and scuffs on the bumper. This paper examines the behavior of specific automobile bumpers in aligned low-velocity collisions. Specifically, empirical data gathered during numerous (currently 660) vehicle-to-vehicle and vehicle-to-barrier collisions are presented and relationships between isolator compression and vehicle impact severity are developed. General trends among all types of isolators and trends specific to vehicle manufacturers are identified and discussed. Damage threshold data are also presented.

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.