In the last few decades a lot of safety equipment has found its way into cars and trucks: side-impact airbags, head curtain airbags, electronic stability control. But a major safety feature has not been upgraded enough some safety advocates argue: The roof.
For the most part the roof protects us from the elements, such as rain or snow. But every so often it plays a far more important role in protecting us in the event of a vehicle rolling over.
In about 2.5 percent of car accidents, the vehicles roll over, according to the National Highway Traffic Safety Administration. That’s a small percentage, but those crashes are deadly. They are responsible for about 10,000 deaths a year, according to the federal agency.
The agency says many of those deaths result from unbelted occupants being thrown from the vehicles. Safety advocates, however, say roof failures play a major part by either coming down on occupants or by making window openings wider, which makes it more likely that occupants can be ejected.
The standard specifying how strong the roofs of cars and light trucks must be was adopted in 1971 and has not been substantially changed since. Testing requires a metal plate to push down on one side of the roof and requires the roof to withstand force equal to 1.5 times the weight of the vehicle.
In 2005 Congress ordered NHTSA to come up with a standard for stronger roofs. At the end of April 2009 the agency finally announced that new standard.
That standard requires vehicles that weigh up to 6,000 pounds to withstand a force equal to three times the weight of the vehicle. For the first time NHTSA also will require heavier vehicles, up to 10,000 pounds, to meet a roof-strength standard, which is 1.5 times the weight of the vehicle on each side of the roof. That leaves plenty of full-size sport-utility vehicles and pickup trucks in a category governed by the current weaker standard.
Safety advocates have been asking for such a test because they say it more realistically duplicates a real-world crash. In a real-world rollover, pressure is put on one side of the roof and then — as the vehicle continues to roll — pressure is applied to the other side of the already weakened roof.
Public Citizen, one group that has advocated stronger roofs, said it was pleased that roofs will now have to resist more weight. But it is unhappy that the test still uses a metal plate pushing down on the stationary vehicle. That’s called a static test.
Public Citizen and the Center for Auto Safety have pushed for a dynamic test in which the vehicle is actually rolled over. They contend such a test would more closely duplicate what happens in the real world. They say a new device called the Jordan Rollover System can accomplish that. But some safety researchers, such as those working at the Insurance Institute for Highway Safety, say nobody has yet worked out all the variables of a dynamic test so that it has consistently repeatable results.
The federal standard does not go into effect until September 2012 and allows automakers to phase in the stronger roofs. The phase-in must be complete by the 2017 model year.
Meanwhile, the insurance institute, which is funded by the insurance industry, has started its own roof-crush tests using a metal plate that pushes down on only one side of the roof. Vehicles are rated on how much force the roof can withstand.
A vehicle that can withstand four times its weight gets a “good” rating. A vehicle that can withstand 3.25 times its weight gets an “acceptable.” A vehicle that can withstand 2.5 times its weight gets a “marginal.” A vehicle that withstands anything less than 2.5 times its weight is rated “poor.”
The institute’s first tests were on 12 small Sport Utility Vehicles from the 2008 and 2009 model years. The Kia Sportage and its sibling the Hyundai Tucson got “poor” ratings. The Ford Escape/Mercury Mariner/Mazda Tribute and Honda’s CR-V got “marginal” ratings. The Suzuki Grand Vitara, the Chevrolet Equinox/Pontiac Torrent, the Toyota RAV4, the Nissan Rogue and the Mitsubishi Outlander all got “acceptable’ ratings.
The top performer was the Volkswagen Tiguan followed by the Subaru Forester, the Honda Element and the Jeep Patriot. All got “good” ratings.
Later this summer the institute will release roof-crush tests of midsize sedans. More information is available at the institute’s web site at www.iihs.org.
Copyright, Motor Matters, 2009