An analysis of vehicle tip stability in NHTSA Side Impact New Car Assessment Program (SINCAP) tests was conducted in order to better understand the causes of possible tip-over in such a test, and the potential relationship to occupant safety. Analyses were conducted of accident data involving light passenger vehicle rollovers. SINCAP tests conducted at several facilities with SUV-type vehicles were reviewed. A computer simulation model of the SINCAP test was developed and used to analyze the effects on vehicle tip-over of variations in vehicle and test facility parameters. It was found that fatal accidents involving “multi-vehicle rollover” (ie, SINCAP like conditions) were the least frequent among four accident types examined; and that SUV’s had the lowest fatality rate in such accidents, among the four vehicle types examined. Also, it was found that tip-over occurrence in the SINCAP test was found to be very sensitive to several unspecified test facility characteristics, which may vary among test facilities; and that it might be possible to “tune” a vehicle for no tipover in the SINCAP test, with little or potentially even adverse effects on actual occupant protection and vehicle safety. Overall it was concluded that the SINCAP test was not suitable for analyzing vehicle rollover potential or rollover safety.