Roof Strength Requirement for Vehicles Involved in Rollover Crash

Rollover crash is one of the most serious safety problems for light weight vehicles. In the USA, rollover crashes account for almost one-third of all occupant fatalities in light weight vehicles. Similar statistics are found for other countries. Thus, rollover crashes have received significant attention in recent years. In the USA and Canada, automotive manufacturers are required to comply with the roof strength requirement of “1.5 times the unloaded vehicle weight” to ensure safety in rollover. NHTSA is currently considering a set of countermeasures to improve the rollover safety, where one of the proposals is to increase the roof strength limit to “2.5 times the unloaded vehicle weight”. This increased roof strength limit seemingly has been motivated based on the benchmark study of current vehicle fleet. While no scientific study is available in the public domain literature showing the inadequacy of the current 1.5 strength factor, several public safety advocacy groups have, nonetheless, asked for even higher load factors (» 2.5) in their responses to the NHTSA's NPRM. The objective of this paper is to present an academic study that was undertaken by the authors to estimate the roof reaction force during vehicle rollover. Results obtained from the analysis of multiple idealized vehicle body models are also presented in this paper.