The Contribution of Vehicle, Occupant and Crash Factors to the Risk of Injury as a Result of Vehicle Rollover: New Approaches to Data and Modeling Analysis

Injuries and deaths as a result of vehicle rollover remain a consistently large contributor of the overall crash fatalities in the United States. While more new vehicles are becoming equipped with electronic stability control and rollover ejection countermeasures as well as increased roof strength, it will take several years of production before these newer vehicles permeate the fleet and the effectiveness of these technologies can be fully assessed. In the interim, continued vigilance on assessment of rollover injury causation is recommended. This can be done through systematic analysis of aggregate field crash data and specific case studies. Also, mathematical modeling studies can be done to assess the contributions of vehicle, occupant and crash factors to the injury risk of rollover involved occupants.

The major aims of the research in this thesis are to determine how rollover crash investigations and crash field data analysis can determine the most frequent types of injuries and their mechanisms that occur to belted, unejected occupants involved in rollover crashes and, once determined, identify the role of vehicle, occupant and crash factors that can predict injury risk. The first aim can be achieved through case studies and aggregate national crash data analysis while the second aim uses finite element and multi-body modeling of rollover crashes.

Aggregate rollover field data was taken from the National Automotive Sampling System – Crashworthiness Data System (NASS-CDS). Head, spine (cervical) and thoracic injuries dominated the injury with specific injury types in each body region indicating areas of further interest to investigate regarding injury causation. Analysis of specific case studies taken from the Crash Injury Research Engineering Network (CIREN) indicated that single event, single vehicle (pure) rollovers were associated with complex mechanisms of cervical spine injuries that were associated with vehicle roof strength (strength to weight ratio), and the amount of vertical as well as lateral intrusion at the injured occupant location. Occupant body mass index was a possible contributor to injury risk.

A finite element model of a contemporary sedan was used in a simulation of a Controlled Rollover Impact System (CRIS) test to identify vehicle and crash parameters that were most associated with high cervical neck forces in the Hybrid III dummy occupant model. The variables that contributed the most to the occupant and vehicle structural response were pitch angle, roll angle, and drop height. These factors determine where and with what force the vehicle roof impacts the ground. The analysis showed that proper selection of a crash dummy model is also a critical step in the interpretation of effects of the factors used in analysis. Subsequent MADYMO modeling of the CRIS test with the models of the Hybrid III and THOR advanced frontal crash dummy and a facet model of the human body were performed with imported finite element nodal vehicle model outputs representing vehicles with the strongest and weakest roof. When coupled with a parameter analysis of advanced vehicle seat belt restraints, the analysis showed that stronger roofs will reduce injury risk, and that restraint systems can provide additional protection to reduce the potential for occupant head impact to the roof.

The analysis approach to both data and modeling in this thesis provided results through innovative combined crash field data analysis, parametric computer modeling methods and statistical and human body modeling techniques to arrive at the conclusions reached. As future vehicle design evolves with respect to automation and other propulsion systems, designers and engineers need to be aware of the structural and occupant restraint requirements these vehicles will need as they interact with the fleet and are exposed to potential rollover situations.

Keywords: Rollover; CIREN; NASS-CDS; Injury Causation; CRIS; Intrusion; Restraints; Kinematics; Roof Inversions; THOR; Global Sensitivity Analysis

Year	Entry
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Year

Entry

1995

Rains GC, Kanianthra JN. Determination of the significance of roof crush on head and neck injury to passenger vehicle occupants in rollover crashes. In: Proceedings of the SAE International Congress & Exposition. February 27–March 2, 1995; Detroit, MI. Warrendale, PA: Society of Automotive Engineers. SAE 950655.

2007

Hu J. Neck Injury Mechanism in Rollover Crashes: A Systematic Approach for Improving Rollover Neck Protection [PhD thesis]. Detroit, MI: Wayne State University; 2007.

1986

Obergefell LA, Kaleps I, Johnson AK. Prediction of an occupant's motion during rollover crashes. In: Proceedings of the 30th Stapp Car Crash Conference. October 27-29, 1986; San Diego, CA. Warrendale, PA: Society of Automotive Engineers:13-26. SAE 861876.

1991

Mackay GM, Parkin S, Morris AP, Brown RN. The urban rollover: characteristics, injuries, seat-belts and ejection. In: Proceedings of the 13th International Technical Conference on Experimental Safety Vehicles (ESV). November 4-7, 1991; Paris, France.741-747.

2003

Bedewi PG, Godrick DA, Digges KH, Bahouth GT. An investigation of occupant injury in rollover: NASS-CDS analysis of injury severity and source by rollover attibutes. In: Proceedings of the 18th International Technical Conference on the Enhanced Safety of Vehicles (ESV). May 19-22, 2003; Nagoya, Japan.