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Physical evidence on the seat belt restraint system is one source of data used by investigators to determine whether or not an occupant was wearing their seat belt during a crash. Evidence of occupant loading on seat belts generated during crash events has been thoroughly researched and is well documented in the literature. However, there is a paucity of data regarding the physical evidence produced when fractured glass is introduced into the restraint system during occupant loading events. The objective of this study is to characterize the physical evidence generated by glass-to-seat belt interaction during low-level impact loading, and compare this evidence with the types of seat belt marks that can be generated inadvertently by accident scene bystanders, emergency responders, and crash investigators. The presence of glass particles in and around the vehicle at the end of a crash event may contribute to the inadvertent generation of physical evidence.

This study investigates the technique used and forces applied on the latch plate and buckle during typical seat belt operation and driving conditions. These techniques and forces are relevant to whether the latch plate can be partially engaged with the buckle during typical operation and whether the latch plate will dislodge during vehicle operation. In addition to studying the insertion of the latch plate, we examined the tensile forces that are applied to the latch plate and buckle during typical, non-crash driving conditions, and how these forces compare to the performance requirements established by the National Highway Traffic Safety Administration (NHTSA) as part of Federal Motor Vehicle Safety Standards (FMVSS) 209. These tensile forces are important in understanding whether the latch plate is likely to dislodge from the buckle if it is in a position of partial engagement.

When an automotive seat belt buckle is believed to have released during a motor vehicle accident, it is typically attributed to one of several potential mechanisms, including inertial release, partial engagement, inadvertent contact, or structural overload. While the majority of literature in the past has focused on the topic of inertial release, little has been written on other release mechanisms. This review paper addresses automotive seat belt buckle release by inadvertent contact between the buckle pushbutton and some other object. This paper describes the conditions that must be satisfied for inadvertent contact to result in buckle release, including release force, direction, and pushbutton travel. We explain the role of occupant kinematics and the likelihood of contact between and occupant's hand or arm and the pushbutton. Occurrences of inadvertent contact in safety testing and a real world case study are presented.