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In rollover accidents, physical evidence of seat belt usage is occasionally difficult to discern. Typically, if a seat belt is used by an occupant in an accident, various seat belt components will display characteristic marks in well-defined locations. These marks are known as “witness marks” or “occupant load marks.” Witness marks in a rollover accident may be faint in comparison to those caused by the occupant restraint forces in high-energy planar collisions. Additionally, in situations where a seat belt buckle is alleged to have unlatched early in a rollover accident, the lack of clear occupant load marks may in some cases be attributed to an alleged “buckle release” that occurred very early in the rollover sequence, so that the seat belt did not sustain loading while in a latched condition.

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.

Pitch-over events are common in motorcycle accidents, and can be caused by impact to the front wheel and occasionally by hard brake application. In either case, the rider of the motorcycle can be propelled over the handlebars as the motorcycle pitches rear-end up. In accidents caused by pitch-over braking, the accident investigator may be faced with limited evidence and then must rely on analyzing the throw distance of the rider in attempting to reconstruct the pre-accident speed of the motorcycle. This analysis can be complicated by the presence of a second rider (the passenger) on the motorcycle. Pitch over caused by front wheel impact can be similarly complex. Although motorcycle deformation as a result of front wheel impact has been studied [1], circumstances surrounding the nature of the deformation, or the impact itself, may require that the trajectory of the rider be analyzed in order to determine the pre-impact motorcycle speed.

The results of a number of previous studies have demonstrated that seat-belted occupants can undergo significant upward and outward excursion during the airborne phase of vehicular rollover, which may place the occupant at risk for injury during subsequent ground contacts. Furthermore, testing using human volunteers, ATDs, and cadavers has shown that increasing tension in the restraint system prior to a rollover event may be of value for reducing occupant displacement. On this basis, it may be argued that pretensioning the restraint system, utilizing technology developed and installed primarily for improving injury outcome in frontal impacts, may modify restrained occupant injury potential during rollover accidents. However, the capacity of current pretensioner designs to positively impact the motion of a restrained occupant during rollover remains unclear.

A MADYMO simulation model was created to analyze the kinematics of a bicycle rider during a frontal collision with a rigid object. The model was validated using a series of crash tests in which rider trajectory was captured with high-speed photography. The test bicycles were equipped with either traditional fixed or suspension front forks. Impact speeds varied from 22.5 to 31.0 kph to cover a range of fork response from minor bending to significant bending and fracture. The predictions of simple particle trajectory analysis were found to approximate rider motion. Rider motion was relatively unaffected by hand and foot “connections” to the bicycle. Furthermore, the rider connection to the bicycle was insufficient to create any significant rider deceleration as a result of bicycle fork deformation.

Three rollcaged and three production roof vehicles were exposed to matched-pair rollover impacts using the Controlled Rollover Impact System (CRIS). The roof-to-ground contacts were representative of severe impacts in previous rollover testing and real world rollovers. The seat belted dummies measured nearly identical head impacts and neck loads with or without the rollcage, despite significant roof crush in the production roof vehicles. Roof crush had no measurable influence on the severity of the head accelerations and neck loads.

Anthropomorphic test dummies (ATDs) have been validated for the analysis of various types of automobile collisions through pendulum, impact, and sled testing. However, analysis of the fidelity of ATDs in rollover collisions has focused primarily on the behavior of the ATD head and neck in axial compression. Only limited work has been performed to evaluate the behavior of different surrogate models for the analysis of occupant motion during rollover. Recently, Moffatt et al. examined head excursions for near- and far-side occupants using a laboratory-based rollover fixture, which rotated the vehicle about a fixed, longitudinal axis. The responses of both Hybrid III ATD and human volunteers were measured. These experimental datasets were used in the present study to evaluate MADYMO ATD and human facet computational models of occupant motion during the airborne phase of rollover.

Vehicle occupants undergo upward and outward excursion during the airborne phase of vehicle rollover due to the inertial effects coming from the vehicle's rotation. When this excursion is sufficient to permit contact between the occupant's head and the vehicle's interior roof panel, the neck may experience compressive loading. This compressive loading, generated during the airborne phase and prior to vehicle-to-ground impact, could render the occupant more susceptible to compressive neck injury during subsequent vehicle-to-ground impacts. In the present study, computational simulations were used to evaluate the effect of steady-state roll rate on compressive preloading in the cervical spine. The results show an increasing relationship between roll rate and compressive preloading when the head contacts the roof panel and becomes constrained.

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.

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.