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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. An analytical effort to understand rollover injuries, using the field accident data of the NASS files and residual headroom as an indicator, was reported by the authors at the 1996 ESV conference in Melbourne, Australia. This paper describes the relationship between roof crush and restrained occupant injury in rollover accidents as derived from the analysis of 1988-1992 NASS files. It extends the residual headroom parameter to the entire population of head, face and neck occupants injured inside the compartment.1

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.

Occupant simulation models have been used to study trends or specific design changes in “typical” accident modes such as frontal, side, rear, and rollover. This paper explores the usage of the Articulated Total Body Program (ATB) as an accident reconstruction tool. The importance of model validation is discussed. Specific areas of concern such as the contact model, force-deflection data, occupant parameters, restraint system models, head/neck loadings, padding, and intrusion are discussed in the context of accident reconstruction.

For twenty years the dynamic test protocol for automotive safety research has been to use an anthropomorphic dummy in sled and crash test simulations. For the past four years, the author and associates have created and used a computer test protocol to model real world accidents and determine injury reduction from potential design modifications without some of the limitations and cost of the physical hardware and test procedure. The computer test protocol is described and examples of the research results in side and rollover accidents are detailed. Preliminary conclusions about injury reduction countermeasures and continuing research are suggested.

This paper describes some human subject experiments in occupant response to rollover with reduced headroom. The results suggest that with a nominal 10 cm of head room, 7.5 to 15 cm of torso excursion in production belts and more than 15 cm of roof intrusion, serious neck injury is likely. Brain damage/head injury is more likely from a combination of roof rail crush and high change of angular roll rate.

Roof strength clearly affects the probability of occupant head and neck injury in light vehicle rollovers. Despite this, most manufacturers continue to design and build vehicles with inadequate roof strength. From experimental and biomechanics evidence and rollover crash data, we present the case that weak, antiquated roof designs contribute to severe head and neck injuries. We discuss the deficiencies in modern roof designs, how they cause severe head and neck injuries, and the limitations inherent in the Federal roof crush standard, FMVSS 216. We describe cost-effective examples of materials and technologies that can provide adequate roof strength to protect occupants in most rollovers without imposing significant weight penalties. Finally, we discuss an approach to dynamic roof strength testing that is based on what occurs in an actual, serious injury-producing rollover.

The relationship between occupant crash injury and occupant compartment intrusion is seen in the perspectives of the velocity-time analysis and the NCSS statistical data for two important accident injury modes, lateral and rollover collisions. Restraint system use, interior impacts, and vehicle design features are considered. Side impact intrusion is analyzed from physical principles and further demonstrated by reference to staged collisions and NCSS data. Recent publications regarding findings of the NCSS data for rollovers, as well as the NCSS data itself, are reviewed as a background for kinematic findings regarding occupant injury in rollovers with roof crush.

Three full-size sedans were towed to highway speeds along a section of a remote rural highway. Upon release, an automated steering controller steered the vehicles through a series of maneuvers intended to result in rollover. Repeated attempts to roll each vehicle were made until rollover resulted. Non-rollover attempts produced cornering tire marks by the out-of-control vehicle. Out of numerous runs, 3 rollover and 2 non-rollover tests were selected for documentation and analysis. One additional steer-induced rollover test is presented that was conducted along a simulated road section at a closed test-track facility. All six tests presented are instrumented real-world type tests that were later reconstructed based upon the data obtained from on-board instrumentation, videotape, survey measurements, and still photographs obtained of each respective test.

A follow-up study on rollover testing was conducted along a section of a remote rural highway using six full-size sport utility vehicles (SUVs) of differing makes and models. The vehicles were instrumented and towed to highway speeds before being released, at which point an automated steering controller steered the vehicles through a series of maneuvers intended to result in rollover. A total of eight tests were conducted and documented, six rollovers and two non-rollover events. The six rollover events provide trip and tumbling conditions for each vehicle. The two non-rollover attempts produced cornering tire marks and allowed for the documentation of near roll conditions for the two out-of-control vehicles. All eight tests presented are instrumented real-world type tests that were later correlated based upon the data obtained.