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It is well known from field accident studies and crash testing that seatbelts provide considerable benefit to occupants in rollover crashes; however, a small fraction of belted occupants still sustain serious and severe neck injuries. The mechanism of these neck injuries is generated by torso augmentation (diving), where the head becomes constrained while the torso continues to move toward the constrained head causing injurious compressive neck loading. This type of neck loading can occur in belted occupants when the head is in contact with, or in close proximity to, the roof interior when the inverted vehicle impacts the ground. Consequently, understanding the nature and extent of head excursion has long been an objective of researchers studying the behavior of occupants in rollovers.

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.

A modeling study was conducted to explore the potential for reducing rollover occupant injury via seat belt geometry modifications and the effect such modifications would have on frontal impact protection. MADYMO software was used to model the first roof-to-ground strike of a dolly rollover crash test as well as a frontal impact test using a facet-style human driver occupant in a sport utility vehicle. The objective of this study was to learn whether occupant protection could be improved for rollover without reducing occupant protection in frontal impact. The models were validated using crash test results. Seat belt anchor locations were independently varied in the models to examine the effects of shortening the length or increasing the angle of the lap belt, shortening the torso belt, or lowering the D-ring. Several combinations of the most promising independent anchor relocations were investigated first in near-side and far-side rollover and then in frontal impact.

For more than 30 years, field research and laboratory testing have consistently demonstrated that properly wearing a seat belt dramatically reduces the risk of occupant death or serious injury in motor vehicle crashes. The emergency-locking portions of seat belt retractors are critical components that engage as a result of vehicle deceleration and lock the retractor as webbing is withdrawn during the onset of occupant loading. The field performance of emergency-locking retractors (ELRs) is commonly called into question. Recent studies have raised concerns about the effectiveness of retractor locking mechanisms in multi-planar collisions, including rollovers. Investigators of vehicle crashes would benefit from samples of diagnostic physical evidence which could be used to assist in distinguishing between an unrestrained occupant, a properly restrained occupant and a restrained occupant where the ELR mechanism was disabled in a crash environment and allowed webbing to “spool-out”.

Previous literature has shown that serious neck injury can occur during rollover events, even for restrained occupants, when the occupant's head contacts the vehicle interior during a roof-to-ground impact or contacts the ground directly through an adjacent window opening. Confusion about the mechanism of these injuries can result when the event is viewed from an accelerated reference frame such as an onboard camera. Researchers generally agree that the neck is stressed as a result of relative motion between head and torso but disagree as to the origin of the neck loading. This paper reviews the principles underlying the analysis of rollover impacts to establish a physical basis for understanding the source of disagreement and demonstrates the usefulness of physical testing to illustrate occupant impact dynamics. A series of rollover impacts has been performed using the Controlled Rollover Impact System (CRIS) with both production vehicles and vehicles with modified roof structures.

Occupant ejection may occur during planar and rollover collisions. These ejections can be associated with serious/fatal injuries. Occasionally, occupants will allege that they were wearing a seatbelt immediately before the ejection occurred. Some accident investigators have opined that a seatbelt became disengaged due to collision forces and/or occupant interactions, leaving the occupant essentially unrestrained and exposed to ejection from the vehicle. We present three case studies of collisions with documented seatbelt disengagement at or during the collision, as well as three controlled tests. The release of the seatbelt was always associated with dire consequences for the occupant's outboard upper extremity. Evidence of seatbelt webbing interaction with the occupant was always evident, and the interaction of the belt with the vehicle interior trim was also apparent.

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.

While previous studies have recognized and demonstrated the upward and outward occupant motion that occurs during the airborne phase of rollover and estimated the resulting head excursion using static and dynamic approaches, the effect of roll rate on restrained occupant head excursion has not been comprehensively evaluated. Moffatt and colleagues recently examined head excursions for near- and far-side occupants resulting from steady-state roll velocities using a laboratory fixture and both Hybrid III anthropomorphic test dummies (ATD) and human volunteers. To expand upon that study, a MADYMO computational model of a rolling airborne vehicle was developed to more thoroughly evaluate the effects of roll rate on occupant kinematics and head excursion. The interior structure of the vehicle used by Moffatt et al. was modeled, and the ATD kinematics observed in that experimental study were used to validate the computational models of the current study.

Rollover crash and accident studies identify significant roof-to-ground impacts adjacent to the vehicle occupant as a potential cause of severe injuries. It is not possible with existing dynamic rollover test methods to specifically repeat or recreate a particular roof-to-ground impact in a controlled fashion. Variations associated with tire-to-dolly, tire/wheel-to-ground, and vehicle-to-ground interactions early in current rollover test methods tend to produce unpredictable and unrepeatable roof-to-ground impacts later in the test. A new test device now enables researchers to bypass the uncertainty of these first ground interactions by beginning each test with the desired roof-to-ground impact conditions as a test input. The new rollover test method releases a rotating vehicle onto the ground from the back of a moving semi-trailer.