Officials Released New Rollover Ranking System. Federal regulators released a new rollover ranking system today to assess the susceptibility of different vehicles to one of the deadliest types of accidents.
The ranking system compares the rollover risk of most 2004 model cars and trucks, offering consumers a precise way to compare a vehicle’s risk of being in a rollover at least by the government’s reckoning in accidents that don’t involve other vehicles.
Previously, the government has used star ratings to indicate rollover risk. That system, which will continue, has been criticized as not providing enough distinction between vehicles, because most earn either three or four stars.
This year, the National Highway Traffic Safety Administration tested 68 new models. Of those, the Ford Explorer Sport Trac, a cross between a pickup and an S.U.V., had the highest rollover risk, with a 35 percent chance of rolling over during a single-vehicle accident.
That is more than four times the risk of the best performer, a four-door Mazda RX-8 sedan, which has about an 8 percent risk, the agency said. Mazda is an affiliate of the Ford Motor Company, which makes the Explorer.
As expected, cars performed much better than S.U.V.’s because they ride closer to the ground and are thus more stable. But the new ratings also show wide differences among vehicles of the same type.
For instance, the Chevrolet Silverado pickup truck, made by General Motors, had ratings ranging from 16 percent to 18.5 percent, compared to rating as high as 28.3 percent for the Toyota Tacoma pickup.
“This is a problem that continues to produce about a third of our occupant fatalities every year, even though they are less than 3 percent of our crashes,” said Dr. Jeffrey W. Runge, the administrator of the traffic safety agency.
The new rankings information, he said, “does arm the consumer with a little more sophisticated information.”
Gloria Bergquist, a spokeswoman for the Alliance of Automobile Manufacturers, said, “It’s difficult to rate an automobile like you rate a movie.”
“This is just one rating,” she added. “We urge people to look at all information and make a judgment, including the front impact and the side impact ratings.”
The new rollover rankings, along with front and side impact test ratings, are available on www.safercar.gov.
The agency also revealed that the Ford Escape S.U.V., and by extension the similarly built Mazda Tribute, tipped up on two wheels during a rollover test. Those vehicles were assessed rollover risks between 21 and 24 percent.
Kristin Kinley, a spokeswoman for Ford, said, “While we believe the N.H.T.S.A. rating system has some value, we don’t think it’s the most effective indicator of how vehicles perform in the real world.”
Consumer groups have said the agency needs to do more to get the ratings to the public.
“We compliment the agency on improving its presentation,” said Joan Claybrook, the president of Public Citizen, but she added that “significant flaws remain.”
She said the information is still not easy enough to find and she wants the agency to create a minimum performance threshold for rollover risk.
While the Explorer Sport Trac was the worst performer overall, the 2004 Subaru Outback wagon ranked as the worst-performing passenger car, a category that includes sedans and station wagons, with a 15.5 percent rollover risk. Its performance was in line with other vehicles that combine aspects of wagons and S.U.V.’s, like the Nissan Murano. The Chrysler Pacifica, one such vehicle, was the best performer among S.U.V.’s, with ratings raging from 13 to 14 percent.
Rollover Accidents Kill 10,000 Americans Per Year
Rollovers accidents, which kill more than 10,000 Americans per year, have been one of the biggest traffic-safety issues in recent years because of the popularity of sport utility vehicles and large pickup trucks. The rollover risks are exacerbated by factors such as drunken driving and people not wearing seatbelts.
While the high ground clearance of sport utility vehicles and pickup trucks can make drivers feel more secure and in control, it also creates a higher center of gravity, leading to less stability. But S.U.V.’s and other light duty trucks are subject to considerably less stringent fuel economy regulations, providing manufacturers a powerful incentive to build them.
Subaru, for instance, has raised the ground clearance of the 2005 model Outback, and made other changes, to reclassify it as a light duty truck and meet the lower standard. A Subaru official said today that the company expects its rollover performance to improve when 2005 models are tested because other dimensions have been changed as well.
The four minivans tested by the agency were assessed rollover risks from 12 to 16 percent, while several S.U.V.’s. had risk ratings above 25 percent, including the Chevrolet Tahoe, GMC Yukon, and some versions of the Ford Explorer and Mercury Mountaineer.
The government started conducting rollover tests this year at the direction of Congress, which ordered the agency to create a track test in the wake of a string of fatal rollover crashes in the late 1990’s involving Ford Explorers equipped with Firestone tires.
In the new tests, vehicles are driven through as many as 10 fishhook maneuvers, a jarring series of turns intended to replicate what happens when drivers momentarily lose control and veer to overcompensate. Last week, G.M. said it would recall its Saturn Vue S.U.V. because its suspension broke during the test.
Previously, the government assessed rollover risk based on a mathematical calculation taking into account a vehicle’s dimensions. That calculation continues to be the agency’s main criteria for assigning risk percentages.
Regulators are also researching adding a handling test with its own star rating. One reason is that changing tire specifications can make a vehicle less prone to rollover but also less maneuverable.
“The idea of the handling test is, you can achieve good rollover resistance by degrading the handling of the vehicle, and that’s not something we want,” said Garrick Forkenbrock, a research engineer at the traffic safety agency. “It’s no good if it’s robbing Peter to pay Paul.”