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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.

The purpose of this study is to evaluate the hard tissue injury -predictive value of various thoracic injury criteria when the restraint conditions are varied. Ten right-front passenger human cadaver sled tests are presented, all of which were performed at 48 km/h with nominally identical sled deceleration pulses. Restraint conditions evaluated are 1) force-limiting belt and depowered airbag (4 tests), 2) non-depowered airbag with no torso belt (3 tests), and 3) standard belt and depowered airbag (3 tests). Externally measured chest compression is shown to correspond well with the pre sence of hard tissue injury, regardless of restraint condition, and rib fracture onset is found to occur at approximately 25% chest compression. Peak acceleration and the average spinal acceleration measured at the first and eighth or ninth thoracic vertebrae are shown to be unrelated to the presence of injury, though clear variations in peaks and time histories among restraint conditions can be seen.

Far-side side impact loading of a seat belt restrained occupant has been shown to lead to torso slip out of the shoulder belt. A pretensioned seat belt may provide an effective countermeasure to torso rollout; however the effectiveness may vary with age due to increased flexibility of the pediatric spine compared to adults. To explore this effect, low-speed lateral (90°) and oblique (60°) sled tests were conducted using male human volunteers (20 subjects: 9-14 years old, 10 subjects: 18-30 years old), in which the crash pulse safety envelope was defined from an amusement park bumper-car impact. Each subject was restrained by a lap and shoulder belt system equipped with an electromechanical motorized seat belt retractor (EMSR) and photo-reflective targets were attached to a tight-fitting headpiece or adhered to the skin overlying key skeletal landmarks.