The National Highway Traffic Safety Administration (NHTSA) has turned down petitions brought by some safety-advocacy groups that had asked the agency to extend its new roof-crush standard to vehicles weighing more than 6,000 pounds. In a report released yesterday, the agency rejected calls for the immediate instatement of a “dynamic” (moving-vehicle) roof-strength test that petitioners had suggested, but indicated that putting a dynamic rollover test into place was the agency’s ultimate goal.
In May 2009, after years of delay, NHTSA upgraded the government safety standard governing roof crush resistance. A crush-resistant roof is an important factor to reduce injury risk in a rollover crash. As such, the minimum roof strength requirement is sometimes called a rollover standard.
The 2009 revisions to the law, Federal Motor Vehicle Standard 216, were the first significant change in 38 years. The new rule says that vehicles weighing 6,000 pounds or less must be able to withstand a force equal to three times their weight applied alternately to the left and right sides of the roof. However, vehicles weighing between 6,000 and 10,000 pounds need only withstand 1.5 times their own weight on the roof.
Petitioners, including the Center for Auto Safety, Advocates for Highway and Auto Safety, and others argued that the same protections afforded people in lighter vehicles should apply to those riding in heavier ones. NHTSA, in its petition denial, pointed out that relatively few vehicles weigh more than 6,000 pounds (and those are usually commercial vehicles). They tend to afford more headspace to start with, and that the cost of reinforcing those vehicles’ roofs would outweigh the benefits. (Only a handful of vehicles we test weigh that much—some heavy-duty pickups and a small number of the largest SUVs.)
Safety advocates have long argued that gently applying weight to a vehicle’s roof--which is how current “static” rollover testing is done--is not a proper approximation of what happens when a speeding car rolls over, especially one that rolls over several times before coming to rest. The problem, however, has been finding a test that actually throws a car onto its roof with repeatable results.
One of the petitioners urging a dynamic test alternative was the Center for Injury Research, which recommended using a specific test machine called the Jordan Rollover System, a device that CfIR uses in its consulting work.
CfIR argued that the Jordan rig produced accurate, reliable, repeatable results. NHTSA disagreed for a number of reasons, including that the test dummy that lab uses wasn’t designed for rollover events.
Good progress has been made by NHTSA on the roof crush standard in the last year. It would seem from the petition response, however, that additional changes to the roof crush standard won’t be immediately forthcoming.
NHTSA has argued that electronic stability control, due to be adopted universally in model-year 2013 vehicles, will, by preventing rollovers in the first place, save more lives than stronger roofs would. That is true. However, we continue to believe that stronger roofs are still a desirable feature.
Last year, the Insurance Institute for Highway Safety (IIHS) introduced its own roof-crush test that subjects a given roof to four times the vehicle’s weight. This new test is now a factor in the coveted IIHS Top Safety Pick designation, along with evaluations of performance front and side impacts, and seat/head restraints. For now, NHTSA’s roof crush standard remains at three times the vehicle’s weight--an improvement over the previous standard, but not as stringent as that suggested by IIHS. Given the high-profile of IIHS, however, the Institute’s test will undoubtedly influence manufacturers to engineer vehicles that eventually meet the higher new standard.