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The role of seatback strength on occupant motion during rear-end collisions has been a focus of scientific investigation for decades. Despite being an integral component of the occupant restraint system, the role of seat belt restraints and the potential effect of various seat belt restraint system components, like pretensioners and latch plate design, on occupant motion and injury potential during rear-end collisions has received less attention. This study identifies and highlights what is currently understood about the role of seat belt restraints and components in rear-end collisions from the existing literature in detail for the first time. Previous studies that have investigated the role of pretensioning in occupant motion and loading did not provide detailed assessments of pretensioning effects on webbing loads and displacement, nor did they discuss the relationship between pretensioner deployment and latch plate design.

This paper investigates the role that load-limiters play with respect to the performance of occupant protection systems, with focus on performance in frontal crashes. Modern occupant protection systems consist of not just the seat belt, but also airbags, interior vehicle surfaces and vehicle structure. Modern seat belts very often incorporate load-limiters as well as pretensioners. Published research has established that load-limiters and pretensioners increase the effectiveness of occupant protection systems. Some have argued that load-limiters with higher deployment thresholds are always better than load-limiters with lower deployment thresholds. Through testing, modeling and analysis, we have investigated this hypothesis, and in this paper we present test and modeling data as well as a discussion to this data and engineering mechanics to explain why this hypothesis is incorrect.

The performance of two types of forward facing child restraint systems (CRSs), belt-positioning boosters (BPBs) and CRSs with an integral 5-point harness were compared in frontal and side-impact testing. Performance criteria in frontal impacts (head injury criteria (HIC), chest acceleration, head excursion and knee excursion) was evaluated by comparing a large set of NHTSA-run FMVSS 213 compliance test data generated with the 3-year-old-sized anthropomorphic dummy (ATD). Side-impact performance was evaluated by conducting a series of sled tests and comparing the relative head excursion of a 3-year-old-sized ATD. FMVSS 213 compliance test data shows that the average HIC, chest acceleration, and head and knee excursions are comparable for BPBs and harness CRSs. ATDs in BPBs experienced a slightly higher average HIC, and a slightly lower average head excursion than ATDs in harness CRSs without a tether.

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.

For over 30 years, there has been a safety standard in the United States that governs the design and performance of child restraint systems, and since 1981 this standard has prescribed dynamic test requirements for the performance of child restraint systems (CRS) in frontal collisions. However, this standard does not include a dynamic test specifically designed to evaluate the performance of CRSs during side impact collisions. One of the reasons a side impact standard has not been implemented is that feasible countermeasures have not been identified. This study addresses this issue by evaluating the effectiveness of padding as a countermeasure in side impact collisions. Head acceleration data were collected during both drop testing and side impact sled testing with and without the use of energy absorbing padding in the CRS side wing.

Forensic evidence left behind in the form of markings on the seatbelt system can reveal details of how the belt system was being used and how it performed in a collision. Information about how belt systems are being used and how they perform in the field is useful to the design engineer, but interpreting this forensic evidence can be very difficult. Most studies to date have looked at the evidence left behind after a collision simply to determine if the seat belt was being used. This study undertakes the next step and addresses the question of how the belt system was being used. Test data is also presented to allow investigators to determine if the retractor locked and remained locked during the collision or if it spooled out during the collision. The results of 22 HYGE sled tests were analyzed to investigate the types and patterns of marks left behind.

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.

The increasing prominence of end-release buckles in automotive restraint systems has been accompanied by criticisms that they are susceptible to inertial unlatching in collisions due to transfer of vertical impulses from the vehicle body or chassis through the buckle stalk to the buckle. It has been asserted that the accelerations imparted to the buckle are significantly amplified relative to the initial input to the vehicle body or chassis. In this study, a test procedure was developed to measure the in-situ dynamic response of restraint system buckles to vertical impulse. The procedure was used to evaluate buckle assembly response to impulses input at, or near, the buckle stalk floor anchors in several vehicles. The advantage of this technique over full-scale drop testing and component-level shock table impacts is that the desired response information may be acquired in-situ without damage to the vehicle.

The Federal Motor Vehicle Safety Standards (FMVSS) include a number of different regulations that are applicable to child occupants. Some of the FMVSS, such as those covering child restraint systems (FMVSS 213) and occupant protection (FMVSS 208), have provisions specifically targeted to children and have been analyzed in the literature. Other FMVSS may not mention children but address aspects of vehicle safety that are relevant to child occupants. This paper examines the full range of occupant-related regulations in the context of how each one affects children. Topics include the use of anthropometric data to analyze restraint regulations (FMVSS 213), a comparison of general seating strength (FMVSS 207) against school bus seating strength (FMVSS 222), and interior trunk releases (FMVSS 401). This paper highlights a number of child occupant safety issues that have been addressed by the FMVSS, as well as others that either already are or will likely be the focus of future rules.

Federal Motor Vehicle Safety Standard No. 213 specifies requirements for child restraint systems used in motor vehicles and was first introduced by the National Highway Safety Bureau in 1971. In 1981, the standard was modified to require dynamic testing of child restraints. Over the following 21 years, Standard No. 213 was modified on numerous occasions, most recently in June of 2003. This paper outlines the history of Standard No. 213 with a discussion of the changes that have been proposed, the comments submitted to NHTSA in response to these proposed changes, and NHTSA's final decision (rule making) regarding which changes to adopt. Detailed discussion is included regarding NHTSA's May 2002 proposal to change the crash pulse, test dummies, injury criteria, and test bench required as part of the dynamic testing. The 2002 proposal also included expansion of the standard to cover child restraints for children weighing up to 65 pounds.

Detailed investigations continually demonstrate that vehicle collision environments are extremely unlikely to produce accelerations of sufficient magnitude and duration to cause inertial release of seat belt buckles. Recently, it has been proposed that the dynamic response of an end-release buckle mounted to the vehicle structure via a metal strap or wire rope can amplify acceleration levels experienced at the floor of the vehicle by a factor of 10 or more, to levels that are high enough to cause inertial release. Experiments and modeling presented here confirm that accelerations may be amplified from the floor of the vehicle to the seat belt buckle, but not by more than a factor of 1.3, and only for acceleration pulse durations that are very short. Shock table testing of end-release seat belt buckles shows that, even with amplification, the resulting buckle accelerations are far below those required to cause inertial release, even at very low webbing tension.