Only one American sport utility vehicle secured a "good"evaluation in the new strength rating system that the InsuranceInstitute for Highway Safety has adopted in a push for a tougherstandard from manufacturers.

The Arlington, Va.-based IIHS said its new measure unveiledtoday is designed to help consumers pick vehicles that will helpprotect them in rollover crashes.

Its initial study of 12 small SUVs found four earning its toprating of "good," with the Volkswagen Tiguan having the strongestroof. The Kia Sportage had the weakest among the 2008-09 modelstested, said IIHS.

The only U.S. SUV to get a good rating was the Jeep Patriot. Twoother rated U.S. SUVs were the Chevrolet Equinox, rated"acceptable," and the Ford Escape, which earned a "marginal"rating.

Also earning good ratings in the IIHS test were the SubaruForester and Honda Element. The Suzuki Grand Vitara, Toyota RAV4,Nissan Rogue and Mitsubishi Outlander were rated acceptable. TheHonda CR-V was rated marginal.

The rating system, which is higher than the government standard,is based on the IIHS research showing that occupants in rollovercrashes benefit from stronger roofs.

Under the IIHS standard, to earn a good rating, the roof mustwithstand a force of four times the vehicle's weight beforereaching five inches of crush. This is a strength-to-weight ratio.Under the Institutes standard, for an acceptable rating the minimumrequired strength-to-weight ratio is 3.25. A marginal rating valueis 2.5. Anything over than that is poor, IIHS said.

In a statement, IIHS President Adrian Lund said thestrength-to-weight ratio of four reflects an estimated 50 percentreduction in risk of serious and fatal injury in single-vehiclerollover crashes compared with the current federal standard of 1.5.The federal standard has not changed since 1973.

"We anticipate that our roof strength test will drive improvedrollover crash protection the same way that our frontal offset andside impact consumer test programs have led to better protection inthese kinds of crashes," said Mr. Lund.

The IIHS said that more than 10,000 people a year are killed inrollover accidents. According to the Institute, stronger roofs canprevent occupants from being crushed by the roof or being ejectedfrom their vehicles because windows, windshields and doors are notbroken.

Tests indicate roofs have gotten stronger over the past fewyears, the IIHS said. The organization said it believes that cardesign improvement to better withstand front and side structuralcollisions has made the difference. Both the Volkswagen and Subaru,which earned good ratings in the roof test, were the first to acethe IIHS front and side tests, Mr. Lund noted.

The National Highway Traffic Safety Administration (NHTSA) hasproposed a new standard, but not as tough as the IIHS'recommendation. The NHTSA argues that upgrading the requirementswould have only a limited impact on rollover deaths and injuries,while the IIHS said its research indicates otherwise

The IIHS said the roof strength rating will be a new requirementto earn its Top Safety Pick award for 2010. Because of the addedrequirement there will be fewer winners in 2010, Mr. Lundpredicted.

The IIHS said it plans to assess the roof strength on mini-carsand midsize cars next.