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Much has been written about reconstruction techniques and testing methods concerning vehicle rollovers. To date, most of the literature describes rollovers as one-dimensional events. Rollovers account for a disproportionate fraction of serious injuries and fatalities among all motor vehicle accidents. The three-dimensional nature of rollover sequences in which a rolling vehicle experiences multiple ground contacts contributes to the environment where such injuries occur. An analytical technique is developed to model the airborne segments of a rollover sequence as a parabolic path of the vehicle center of gravity. A formulation for the center of gravity descent from maximum elevation to full ground contact is developed. This formulation contains variables that may be readily determined from a thorough reconstruction. Ultimately, this formulation will also provide a vertical ground impact velocity at contact.

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.

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.

To date, the most commonly used rollover test device has been the rollover dolly described in the SAE J2114 recommended practice, which is commonly referred to as the “208 rollover dolly.” However, for a number of reasons, the rollover dolly has never been accepted as a standard for rollover testing. One of the primary limitations of the rollover dolly has been the controllability of the first roof-to-ground impact. A new rollover test device, known as the Controlled Rollover Impact System (CRIS), was presented at the SAE Congress in March 2001. This device allows the roll, pitch, and yaw angles, roll rate, translational velocity, and drop height of the vehicle to be specified for the first roof-to-ground impact. One objective of the current study was to compare the vehicle dynamics produced by each test device using an Econoline-350 van as the test vehicle.

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.

A follow-up case study on rollover testing with a single full-size sport utility vehicle (SUV) was conducted under controlled real-world conditions. The purpose of this study was to conduct a well-documented rollover event that could be utilized in evaluating various methods and techniques over the phases associated with rollover accidents. The phases documented and discussed, inherent to rollovers, are: pre-trip, trip, and rolling phases. With recent advances in technology, new devices and techniques have been designed which improve the ability to capture and document the unpredictable dynamic events surrounding vehicle rollovers. One such device is an inertial measurement unit (IMU), which utilizes GPS technology along with integrated sensors to report and record measured dynamic parameters real-time. The data obtained from a RT-4003 IMU device are presented and compared along with previous test data and methodology.

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.

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.

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.

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.