Arlington, Virginia – The U.S. Insurance Institute for Highway Safety (IIHS) has launched a new roof strength rating system that will help consumers pick vehicles that will help protect them in rollover crashes. The new system is based on IIHS research that showed occupants in rollover crashes benefit from stronger roofs.
Vehicles rated “good” must have roofs that are more than twice as strong as minimum federal safety standards require.
The IIHS’ first test involved twelve small SUVs, of which four earned the top rating of “good”. The Volkswagen Tiguan had the strongest roof, while the Kia Sportage had the weakest, among the 2008-2009 models evaluated.
The VW Tiguan, Subaru Forester, Honda Element and Jeep Patriot earned “good” ratings, while the Suzuki Grand Vitara, Chevrolet Equinox, Toyota RAV4, Nissan Rogue and Mitsubishi Outlander were rated “acceptable.” The Honda CR-V and Ford Escape rated “marginal,” while the Kia Sportage was “poor.”
“We anticipate that our roof strength test will drive improved rollover crash protection the same way our frontal offset and side impact consumer test programs have led to better protection in these kinds of crashes,” said IIHS president Adrian Lund. “It’s not surprising that Volkswagen and Subaru earn good ratings in our new roof test, because these automakers were among the first to ace our front and side tests.”
IIHS research indicates that roofs are gotten stronger during the past few years, partly because manufacturers have made structural improvements to earn better front and side ratings in IIHS crash tests. Strong A and B pillars help prevent intrusion in these types of crashes, and also help hold up the roof.
The Institute said that more than 10,000 people per year are killed in the U.S. in rollovers, and that when vehicles roll, their roofs hit the ground, deform and crush. Stronger roofs crush less, reducing the risk that people will be injured by contact with the roof itself, and can help prevent occupants from being ejected, especially those not wearing seatbelts. Any vehicle can roll in a crash, but the problem is worse in some types of vehicles: about 25 per cent of occupant deaths in crashes of cars and minivans involve rolling over, while SUVs jump to 59 per cent.
The roof strength test involves pushing a metal plate against one side of the roof at a constant speed. To earn a “good” rating, the roof must withstand a force of four times the vehicle’s weight before reaching five inches (127 mm) of crush, known as a strength-to-weight ratio. For an “acceptable” rating, the minimum required strength-to-weight ratio is 3.25. A “marginal” rating is 2.5, and anything lower than that is “poor.”
Cars have been built to meet the same roof crush standard since 1973. The rule was extended in 1994 to include all passenger vehicles up to a gross weight of 6,000 lbs (2,721 kg). Many SUVs and pickups are heavier and so are exempt. In 2005, the government proposed an upgrade to cover these larger vehicles, and require the roofs on all passenger vehicles to have a strength-to-weight ratio of 2.5. The IIHS said that many vehicles already meet this ratio, and would earn only a “marginal” rating in its new roof test. A final government rule is still pending.
For 2010, a “good” roof strength rating will be a new requirement to earn the IIHS’ Top Safety Pick Award, which was also amended for 2007 to require available electronic stability control.