Given an adequate structural design, low mass vehicles can exhibit a level of passive safety comparable to their heavier counterparts, even in frontal crashes against vehicles twice their mass. The high car mean acceleration levels (50 g) and velocity change (delta V of 20 m/s) observed in such collisions demand for an optimisation of their restraint systems. It has been shown in earlier tests that especially the distance between chest and steering wheel, which is defined by ergonomical constraints, is insufficient in a low mass vehicle under these crash circumstances. The steering wheel must therefore yield during the crash, preferably through an energy absorbing mechanism. The belt system must in return allow for an increased forward displacement of the occupant without intolerable belt force levels. Optimisation of the key components of such a restraint system is solvable only with the extensive use of computer simulation in combination with single component tests and sled experiments. A restraint system meeting the occupant protection requirements is presented. In sled tests, a collision with a delta V of 77 km/h was simulated, yielding tolerable injury protection criteria for the Hybrid III 50% dummy. (A)
Abstract