This paper examines NASS/CDS 1995 to 2001 in order to evaluate rollover crash severity metrics and to recommend additional data elements to assist in determining rollover severity.
For belted occupants and unbelted ejected occupants in single vehicle crashes, the number of roof impacts is an appropriate severity indicator. For ejected occupants, the ejection risk generally increases with the number of quarter-turns. However, number of roof impacts provides a more uniform relationship between crash severity and injury risk.
For the population of crashes with another vehicle prior to rollover, the injury risks are higher than for single vehicle crashes. Impacts with a fixed object such as a tree or wall prior to rollover also carry higher injury risks. Consequently, additional severity measures such as the delta-V for the pre-rollover crash event are required in addition to the rollover severity measures.
For non-ejected unbelted occupants in single vehicle crashes, the most frequent and most injurious category was one quarter-turn. An examination of cases with one quarter-turn showed that the majority of the injuries were in rollovers that were stopped by impacts with trees and poles. In most of these cases, the point of impact was the roof. Additional data elements to permit easy identification of rollover cases that also involve planar crashes with fixed objects during the rollover would be desirable. Crash severity metrics associated with planar crashes may be applicable to these cases.