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The government, automotive industry and scientific community are currently scrutinizing the adequacy of the FMVSS #216 roof crush standard in the United States. As a result of concern about the ability of FMVSS #216 to enforce reasonable protection to occupants in rollovers, The National Highway Traffic Safety Administration (NHTSA) has recently published a Request For Comments in the Federal Register regarding updating this standard1. The inverted drop test methodology is a promising alternative test procedure to evaluate the structural integrity of roofs and is being considered by NHTSA as a possible compliance test. Recent testing on many different vehicle types indicates that damage consistent with field rollover accidents can be achieved through inverted drop testing at very small drop heights. Drop tests matrices were performed on 9 pairs of vehicles representing the majority of personal transportation vehicle types.

Accident reconstruction analysis of both pre- and post-impact vehicle trajectory wherein an involved vehicle has collided with or traversed a roadside curb often leaves the analyst with uncertainty associated with the speed loss and accelerations attributable to these impacts. A review of available published data reveals very few studies considering the energy dissipated and transferred to the vehicle's occupants. This paper quantifies the changes in vehicle velocity (delta-v) for various vehicles traversing a typical roadside curb at various approach angles and impact speeds. Vehicle accelerations are recorded in the vertical, longitudinal, and lateral directions. Resulting three-point belted driver movements are observed via an interior mounted video camera and general occupant motions are described. Curb impacts were conducted with four different passenger vehicles ranging in size from a small compact car to a large full-size sport utility vehicle.

Inverted drop testing of vehicles is a methodology that has long been used by the automotive industry and researchers to test roof integrity. In our laboratory, the inverted drop test methodology was employed on late model production vehicles to simulate the damage incurred by a real world rollover accident. The extent and shape of residual damage matched well with the corresponding accident damage. Modified vehicles were reinforced based upon previously documented techniques. Incorporation of these techniques demonstrated a significant increase in roof strength and corresponding reduction in roof crush with minor weight addition. Finally, a production vehicle and structurally enhanced vehicle were drop tested with instrumented Hybrid-III occupants. This pair of tests confirms that reduction of roof intrusion and increased headroom can significantly enhance occupant protection. It also highlights the need to maintain adequate survival space for the vehicle’s occupants.

Contemporary production emergency locking seatbelt retractors (ELRs) have been proven very effective in the crash environment for which they have been primarily designed and most adequately tested, that is, in the full frontal crash mode. However, researchers have documented spool out during offset, angled, override, underride, and rollover crashes where seatbelt retractors are subject to acceleration pulses in varying directions, including the vertical plane. Occupant motions during these real world accident modes may also impart loads into the belts and belt hardware (webbing and buckle assemblies) that may not be immediately apparent in the frontal barrier test mode. Numerous laboratory studies have demonstrated that the inertial sensor can be held in the neutral position when an overriding opposing force is applied to the retractor, resulting in webbing spool out. Various ELR designs include ball and cage sensors, pendulum, and disk systems.

The Federal Motor Vehicle Safety Standard 571.201 discusses occupant protection with interior impacts of vehicles. Recent rule making by the National Highway Traffic Safety Administration (NHTSA) has identified padding for potential injury reduction in vehicles. Head injury mitigation with padding on vehicular roll bars was evaluated. After market 2 to 2.5 cm thick padding and metal air gap padding reduced the head injury criterion (HIC) and angular acceleration compared to the stock foam roll bar padding. Studies were conducted with free falling Hybrid 50% male head form drops on the fore head and side of the head. Compared to the stock roll bar material, a nearly 90% reduction in HIC was observed at speeds up to 5.4 m/s. A concomitant 83% reduction in angular acceleration was also observed with the metal air gap padding. A 2 to 2.5 cm thick Simpson roll bar padding produced a 70 to 75% reduction in HIC and a 59 to 73% reduction in angular acceleration.

There is little debate that reconstructing a rollover crash presents complex multi-dimensional challenges to the reconstructionist. Real world rollovers often cover large amounts of various terrains and typically involve multiple ground impacts. The possible vehicle orientations throughout the roll are almost unlimited. It is also clear that the complexities of these events have placed practical limitations on the abilities for both analytical and experimental models to accurately recreate specific real world rollover collisions. The fundamentals of accident reconstruction do still apply, however, and much valuable and insightful test data is available. This paper will describe a practical methodology and protocol to assist reconstructionists in reconstructing both on-road and off-road rollover accidents.

In this study we continue and build upon previous research conducted with various production three-point restraint systems; studying resulting vertical excursion on restrained inverted occupants. Vertical excursions will be reported for various sized occupants restrained by both production vehicle belt systems as well as systems incorporating alternative designs. Vertical excursions have been reduced by an average of 77% with optimized belt geometry combined with belt pretensioning.

Rollover accidents account for a large number of serious to fatal injuries annually. In the past, these injuries were often the result of unrestrained occupant ejection. Subsequent to mandatory belt use laws, a larger percentage of these injuries occur inside the vehicle, and the head and neck areas sustain a substantial number of these injuries. Rollovers have been characterized as violent events, roof crush as the natural consequence of such violence. Further, head and neck injury have been thus considered unavoidable, even with occupant use of the production restraints. This paper will describe the relationship between the three dimensional extent (severity) of roof crush and the equivalent drop test contact velocity as derived from physical experiments and tests. The drop test contact velocity is directly related to the cumulative change of velocity experienced by a vehicle as a result of roof contact deformation during a rollover accident by validated computer simulations.

Experimental results from three point bending and axial compression tests of common automotive roof elements are presented. Modifications of these components were also tested to evaluate the effect of structural reinforcements and void filling. Under three-point bending, an open hat section side header (or side rail) was tested and failed in a manner consistent with observed failures in real world accidents. Modifying the hat section to create a closed section increased load capacity and energy absorption, and demonstrated some gains in strength to weight performance. Two epoxy compounds in a similar closed section configuration resulted in substantial increases in peak load, energy absorption and strength-to-weight ratio. In the axial compression tests, a open “c” section front header were tested in axial compression and failed just past a sheet metal reinforcement consistent with observed failures in real world accidents.