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Accident data suggest that a significant percentage of rear impacts involve occupants seated in other than a “Normal Seated Position”. Pre-impact acceleration due to steering, braking or a prior frontal impact may cause the driver to move away from the seat back prior to impact. Nevertheless, virtually all crash testing is conducted with dummies in the optimum “Normal Dummy Seated Position”. A series of 7 rear impact sled tests, having a nominal AV of 21 mph, with Hybrid III dummies positioned in the “Normal Dummy Seated Position”, “Out of Position” and slightly “Out of Position” is presented. Tests were performed on yielding production Toyota and Mercedes Benz seats as well as on a much stiffer modified Ford Aerostar seat. Available Hybrid III upper and lower neck as well as torso instrumentation was used to analyze and compare injury potential for each set of test parameters.

The assessment of seat belt usage during a collision is typically made by considering four types of evidence: (1) the nature and location of the occupant’s injuries, (2) the presence or absence of occupant contact marks in the passenger compartment, (3) the occupant’s final position and (4) markings on the restraint system. This paper focuses specifically on seat belt restraint system markings. Markings or observable anomalies on the webbing and restraint system hardware can be classified into two categories: (1) those caused by collision forces, or “loading marks” and (2) those created by noncollision situations, or “normal usage marks”. Some normal usage marks can appear visually similar to loading marks. The purpose of this paper is to help the investigator distinguish between occupant loading marks and normal usage marks by presenting examples of marks found on belt restraint systems that have never experienced occupant loading in a collision.