Why does IIHS rate roof strength?
The Institute generally supported NHTSA’s initial proposal in 2005 but noted a “surprising lack of evidence” that the federal test procedure was in any way related to protection in real-world rollovers. Without knowledge of such a relationship, it is not possible to determine an adequate level of roof strength for the vehicle fleet. Based on the need for real-world crash data, the Institute studied the relationship between roof strength measurements using the FMVSS 216 procedure and the risk of injury or death in rollovers.15 The 2008 study found that strong roofs significantly reduce the risk of injury or death in rollover crashes, and this was confirmed by a second IIHS study using a different set of vehicles with strengths up to 4 times their weight.16 Both studies found that strong roofs reduce the risk of ejection and the risk of injury for non-ejected occupants. Based on these findings, the lack of consumer information on roof strength, and continued delays in the rulemaking proc
