Search Results

During a rollover accident the position of an occupant within a vehicle at the time of vehicle-to-ground contact affects the occupant's injury potential and injury mechanisms. During rollovers, the accelerations developed during the airborne phases cause an occupant to move away from the vehicle's center of mass towards the perimeter of the vehicle. The occupant is already in contact with vehicle structures during upper vehicle structure-to-ground impacts. The location and extent of the occupant-to-vehicle contacts and the times and locations at which the contacts occur depend upon a variety of factors including occupant size, initial position in the vehicle, restraint status, vehicle geometry, and rollover accident parameters. Onboard and offboard video of existing dolly rollover studies, specifically the “Malibu” studies, were examined to quantify the motion of the occupants' heads and determine the timing and locations of head contacts to the vehicle perimeter.

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.

Occupant kinematics during rollover motor vehicle collisions have been investigated over the past thirty years utilizing Anthropomorphic Test Devices (ATDs) in various test methodologies such as dolly rollover tests, CRIS testing, spin-fixture testing, and ramp-induced rollovers. Recent testing has utilized steer maneuver-induced furrow tripped rollovers to gain further understanding of vehicle kinematics, including the vehicle's pre-trip motion. The current study consisted of two rollover tests utilizing instrumented test vehicles and instrumented ATDs to investigate occupant kinematics and injury response throughout the entire rollover sequences, from pre-trip vehicle motion to the position of rest. The two steer maneuver-induced furrow tripped rollover tests utilized a mid-sized 4-door sedan and a full-sized crew-cab pickup truck. The pickup truck was equipped with seatbelt pretensioners and rollover-activated side curtain airbags (RSCAs).

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.

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.

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.

This study assesses vehicle and occupant responses in six vehicle-to-vehicle high-speed rear impact crash tests conducted at the Exponent Test and Engineering Center. The struck vehicle delta Vs ranged from 32 to 76 km/h and the vehicle centerline offsets varied from 5.7 to 114 cm. Five of the six tests were conducted with Hybrid III ATDs (Anthropometric Test Device) with two tests using the 50th male belted in the driver seat, one test with an unbelted 50th male in the driver seat, one test with a 95th male belted in the driver seat, and one with the 5th female lap belted in the left rear seat. All tests included vehicle instrumentation and three tests included ATD instrumentation. The ATD responses were analyzed and compared to corresponding IARVs (injury assessment reference values). Ground-based and onboard vehicle videos were synchronized with the vehicle kinematic data and biomechanical responses.

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.