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. A survey of the driver’s belt system in 307 vehicles was conducted. Forty examples of a variety of normal usage marks are illustrated.
The most commonly observed types of normal usage marks were: grooves, buffing, abrasions and grime buildup on the D-ring and latch plate; scratches on the latch plate tongue; fiber disruptions, staining, transfers or discolorations, cupping, folding and fraying on the webbing; latch plate tongue insertion marks, and contact marks on the buckle from the console, seat or occupant; and transfers or abrasions on other interior surfaces from interaction with restraint system components.