Less than two months after the U.S. Department of Transportation's National Highway Traffic Safety Administration (NHTSA) announced that it would delay finalization of tougher roof-strength standards, the nongovernmental Insurance Institute for Highway Safety (IIHS) has indicated that it will introduce a rating system for roof strength to help consumers in their selection of a new vehicle.
Currently, the IIHS tests and rates vehicles for front, side, and rear impact protection. According to Spokesman Russ Rader, the IIHS will rate vehicles for roof strength beginning with the 2010 model year. To earn a "good" rating, a vehicle must have a strength-to-weight ratio (SWR) of 4.0, which means the roof must be strong enough to withstand four times the weight of the vehicle.
The current federal standard is 1.5 SWR, although NHTSA is finalizing plans to increase that figure to 2.5. Whereas the IIHS standard is strictly an aid for consumers, the federal standard is a minimum requirement for the vehicle to be sold. Fine-tuning of the IIHS rating system is continuing, and there will be a minimum strength requirement for a vehicle to earn the organization's Top Safety Pick award. IIHS is developing its rating system based, in part, on a study presented Feb. 5 at SAE International's Government-Industry Meeting in Washington, D.C. The study spells out the safety benefits of stronger roofs.
The IIHS roof test setup will be the same as the one used by NHTSA for vehicle compliance with Federal Motor Vehicle Safety Standard 216. In the test, a metal plate is forced into one side of the roof at a constant speed, according to IIHS's Rader. The roof must crush no more than 5.0 in (127 mm) to pass the test.