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Markings or observable anomalies on seat belt webbing and hardware can be classified into two categories: (1) marks caused by collision forces, or “loading marks”; and (2) marks that are created by non-accident situations, or “noncollision marks”. In a previous work, a survey of the driver's seat belt of 307 vehicles that had never experienced a collision was conducted, and several examples of marks created by normal, everyday usage, or “normal usage marks” were presented. It was found that some normal usage marks were visually similar to loading marks. This paper presents several examples comparing loading marks to visually similar normal usage marks and discusses the important similarities and differences.

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.