IIHS tested 12 small SUVs to determine roof strength by crushing the driver's side five inches and measuring the applied pressure.

You can add roof strength to the tests performed by the Insurance Institute for Highway Safety, and with it comes another rating that consumers can use to evaluate their choices when shopping for a vehicle. To kick things off, the institute tested 12 small SUVs. The results are not pretty.

Four of 12 received a rating of “Good,” five were “Average,” two were “Marginal” and one was “Poor.” The institute’s rating system requires the roof to be more than twice as strong as the current minimum federal safety standard. With 10,000 deaths a year in rollovers, the institute recommends a tougher standard than the one proposed by the government, which has been languishing since it was first proposed in 2005. More about that later.

Receiving the top rating of Good were the Volkswagen Tiguan, Subaru Forester, Honda Element and Jeep Patriot. The Suzuki Grand Vitara, Chevrolet Equinox/Pontiac Equinox, Toyota RAV4, Nissan Rogue and Mitsubishi Outlander all earned an Average rating. Those earning a marginal rating were the Honda CR-V and Ford Escape/Mazda Tribute/Mercury Mariner. Taking the ignominious honor of a Poor rating was the Kia Sportage/Hyundai Tucson.

The test itself is performed by applying pressure with a metal plate to one side of the roof at a constant speed. For a Good rating, the roof must withstand a force of 4.0 times the vehicle’s weight before reaching five inches of crush. Strength-to-weight ratios are 3.25 for Acceptable, 2.5 for Marginal. Below a 2.5 ratio, the rating is Poor.



It is a static test, and therefore doesn’t factor in the effectiveness of restraint systems like safety belts, rollover curtain airbags, and padding in vehicle interiors. While a dynamic test could provide more data, just how such a test should be conducted is a matter of debate. The institute points out that rollover accidents don’t have a single cause. Often the roll is preceded by another incident, in which vehicle occupants change position before the roll. In addition, none of the existing crash test dummies are designed to evaluate what happens in a rollover.

Returning to the issue of an appropriate standard, IIHS is at odds with a proposal by the National Highway Traffic Safety Administration. The current standard dates to 1973, and requires a vehicle to withstand 1.5 times its curb weight with testing on one side. In 2005, Congress directed the Transportation secretary to address the issue. The initial proposal called for increasing the standard to 2.5 times the vehicle’s curb weight and extends the rule to vehicles with gross weight ratings up to 10,000 pounds.

A supplemental proposal was added in January 2008 to crush vehicle roofs on driver and passenger sides. The deadline for a final standard was July 1, 2008. But Mary Peters, Transportation secretary in the Bush Administration, said in June there would be a delay until October. Then it was supposed to be out in mid-December, and finally she postponed it until the end of next month. Perhaps to allow the incoming administration the opportunity to evaluate and implement the standard, or perhaps to avoid getting embroiled in the auto industry’s financial troubles by implementing a potentially expensive regulation.

NHTSA argues that increasing the standard won’t save that many lives—45 a year out of the current annual average of 10,000 deaths. IIHS counters with the argument that the government excluded too many factors.

“The agency made too many unproven assumptions about the relationship between roof strength and injury risk,” IIHS President Adrian Lund said. “For example, if someone was ejected during a rollover, NHTSA ignored the possibility that this wouldn’t have occurred if the roof had held up better. Based on this one flawed assumption, the agency eliminated more than a third of all deaths as potential beneficiaries of stronger roofs.”

Other scenarios were discarded by NHTSA to the point where, Lund says, “The agency discarded 94 percent of rollover deaths.”

The industry is, unsurprisingly, resistant to a tougher standard. In an argument presented by the Alliance of Automobile Manufacturers, the industry claims that roof strength has no relation to the risk of injury in a rollover accident. As preposterous as that sounds, Robert Strassburger, vice president of vehicle safety and harmonization for the AAM, told a Senate subcommittee just that at a hearing in June 2008. They parsed accident data and came up with this conclusion: “… [T]he risk of serious head/neck/face injury for belted occupants, even after controlling for rollover class, driver age, and belt use.”

Steve Oesch, senior vice president of the Institute’s insurer and government relations, said earlier studies’ findings “defy logic” because “in every other crash configuration—whether front, side, or rear—the basic principles of occupant protection dictate that the compartment be designed to resist intrusion so lap/shoulder safety belts and airbags can provide protection to occupants. There is no logical reason to assume that in a rollover crash you would design a vehicle to permit excessive intrusion.”

Meanwhile, a NHTSA spokesman says the new proposal is on track to meet the April 30th deadline.