Rollover Ratings Released
WASHINGTON--Two General Motors sport utility vehicles have scored the lowest in the first-ever rollover resistance ratings issued by the National Highway Traffic Safety Administration. NHTSA’s ratings program is designed to provide consumers with a measure of a vehicle’s resistance to rolling over in a single vehicle crash. However, the ratings system is being criticized by safety groups as being too simplistic.
The Transportation Department gave one-star ratings to the Chevrolet Blazer and GMC Jimmy/Envoy four-door 4X4 SUVs. The Ford Explorer 4X4 SUV, the target of numerous of lawsuits as a result of rollover crashes, was rated two stars.
Among the first vehicles rated, only one, the Honda Accord, received five stars. All of the other passenger cars rated to date received four stars. In addition, the Chrysler PT Cruiser, Honda Odyssey, Chevrolet Silverado Extended Cab 4x2, and the GMC Sierra Extended Cab 4x2 received a four star rating.
One vehicle, the Ford Focus, has Electronic Stability Control, a device which does not affect the Rollover Resistance Rating directly but may reduce the likelihood of a single vehicle crash, and thus, the risk of subsequent rollover. NHTSA will note vehicles equipped with Electronic Stability Control in all future Rollover Resistance Ratings announcements. Only one vehicle among three dozen 2001 models tested, the four-door Honda Accord, received the top rating of five stars.
“By providing consumers with information about the comparative rollover risk of various types of vehicles, they will be better able to choose a safe vehicle for themselves and their family,” said U.S. Transportation Secretary Rodney E. Slater. “By providing consumers with additional information, we can motivate manufacturers to respond with safer, more stable vehicles.''
The program gives its star ratings for rollover resistance as part of the agency’s New Car Assessment Program (NCAP).
More than 10,000 people die every year in rollover crashes, according to NHTSA. More than 60 percent of the SUV occupants killed in 1999 died in crashes when their vehicle rolled over, compared to 23 percent for car occupants.
NHTSA Administrator Dr. Sue Bailey said that with the rollover resistance ratings, NHTSA is providing consumers with information about one of the deadliest types of crashes.
NHTSA expects motivated manufacturers will respond to consumer demand for safer, more stable vehicles. In 1979 when NCAP ratings for frontal crashes began, just 33 percent of vehicles achieved a four- or five-star rating. By 1997, 85 percent had received four or five stars.
Bailey emphasized that the best consumer advice about rollover is the dramatic effect of seat belts. “Your best chance of surviving a rollover is by buckling up. Eighty percent of the people killed in single vehicle rollovers were unbelted, and we know that belted occupants are about 75 percent less likely to be killed in a rollover crash than unbelted occupants,” Bailey said.
The Rollover Resistance Rating is an estimate of the risk of rolling over if a person has a single vehicle crash, usually when the vehicle runs off the road and is tripped by a curb, ditch or soft soil. It does not predict the likelihood of that crash. The Rollover Resistance Rating is based on the “static stability factor,” a measure of a vehicle’s center of gravity and track width to determine how “top-heavy” the vehicle is. The more top-heavy the vehicle, the more likely it is to roll over. The lowest-rated vehicles (one star) are at least four times more likely to roll over than the highest-rated vehicles (five stars). Here is the five star rating system:
In a single vehicle crash, a vehicle with a rating of:
Five Stars - ***** Has a risk of rollover of less than 10 percent
Four Stars - **** Has a risk of rollover between 10 percent and 20 percent
Three Stars - *** Has a risk of rollover between 20 percent and 30 percent
Two Stars - ** Has a risk of rollover between 30 percent and 40percent
One Star - * Has a risk of rollover greater than 40 percent
The agency expects to issue rollover resistance ratings for more than 80 Model Year 2001 vehicles by April of 2001. Ratings will be posted on the NHTSA website www.nhtsa.dot.gov as they become available. Meanwhile, the Consumers Union, publisher of Consumer Reports magazine, says it is dissatisfied with the new system for rating rollover risks.
After an initial review of the new ratings system, CU repeated its concerns that NHTSA has based its rollover rating system solely on the vehicle’s so-called static stability factor (SSF), rather than basing it on driving tests and the dynamic performance of the vehicles.
“While we believe that providing consumers some information is preferable to providing no information at all, Consumers Union has serious reservations about using a static measure such as SSF to determine for comparative purposes the stability of vehicles.” said Dr. R. David Pittle, CU’s senior vice president and technical director.
Pittle pointed out that SSF utilizes only two aspects of the vehicle, both of which are static measurements--the center of gravity height and the track width. (SSF is calculated as T/(2H), T being the track width and H being height above the ground of the vehicle’s center of gravity with one or more occupants in place). Important vehicle-design elements such as the suspension, tire design and steering response affect a vehicle’s stability and differ from vehicle to vehicle--but are not accounted for by SSF, he said.
“There is no real way to know how a vehicle will act in an emergency situation by simply measuring its shape at rest,'' Pittle said. “We must see how it performs when it is driven, when the whole vehicle is acting as a complete dynamic system. We are encouraged that under the recent TREAD Act, Congress has directed NHTSA to develop a dynamic test for vehicle stability.”
CU has been in the forefront of testing vehicles for routine handling and emergency handling, as well as braking, acceleration, fuel economy, comfort and convenience, he said The test results appear in Consumer Reports magazine and other CU publications.
In 1996 CU petitioned NHTSA to develop a consumer information program that provided comparative data on the rollover risks of SUVs based on dynamic testing--that is, a program based on actual driving tests.
NHTSA granted CU’s petition. However, CU was disappointed last May when it learned that NHTSA had abandoned its plans for dynamic testing in favor of a static formula such as SSF, which CU believes is too coarse a measure to compare vehicle stability within the same class of vehicles, Pittle said.
Last year, Congress passed an auto safety law called the TREAD Act (Transportation Recall Enhancement, Accountability and Documentation Act). The law directs NHTSA to develop a dynamic test for rollover risks to be used as the basis for its consumer information program.
“We applaud Congress for its efforts to uphold and improve the government ratings for rollover risks. When NHTSA develops a valid dynamic test, the results should provide a far more accurate measure of vehicle stability than what is being offered today,'' said Sally Greenberg, senior product safety counsel for CU.
In comments filed with NHTSA last August, CU noted that, despite its reservations about SSF, the static measure does have some positive attributes.
“The SSF metric shows the importance of vehicle load conditions. We note that on NHTSA’s website, the SSF rating for a given vehicle, particularly SUVs and minivans, may vary depending on whether the vehicle is carrying a full load of passengers and cargo. When loaded, many of these vehicles drop one star in NHTSA’s rating. SSF could also be a useful element of evaluating the propensity for tripped rollovers, but needs to be used in conjunction with a dynamic stability test,” said David Champion, director of CU’s Automotive Testing Division.
The first set of NHTSA ratings for model year 2001 vehicles follows:
Model Year 2001 Rollover Resistance Ratings
2001 Light Passenger Cars
(2000-2499 lbs. curb weight)
Ford Focus 4DR 4 stars
2001 Compact Passenger Cars
(2500-2999 lbs. curb weight)
Chevrolet Cavalier 4DR 4 stars
Honda Civic 4DR 4 stars
Pontiac Sunfire 4DR 4 stars
Volkswagen Jetta 4DR 4 stars
2001 Medium Passenger Cars
(3000-3499 lbs. curb weight)
Chevrolet Impala 4DR 4 stars
Ford Taurus 4DR 4 stars
Honda Accord 4DR 5 stars
Mercury Sable 4DR 4 stars
2001 Sport Utility Vehicles
Chevrolet Blazer 4DR 4x2 1 star
4DR 4x4 2 stars
Chevrolet Suburban 4x4 3 stars
Chevrolet Tahoe 4DR 4x4 3 stars
Chevrolet Tracker 4DR 4x2 3 stars
4DR 4x4 3 stars
Ford Expedition 4x2 2 stars
Ford Explorer 4x4 2 stars
GMC Jimmy/Envoy 4DR 4x2 1 star
4DR 4x4 2 stars
GMC Yukon 4DR 4x4 3 stars
GMC Yukon XL 4x4 3 stars
Honda CR-V 4x4 3 stars
Jeep Grand Cherokee 4x4 2 stars
Lincoln Navigator 4x2 2 stars
Mercury Mountaineer 4x4 2 stars
Mitsubishi Montero Sport 4x4 2 stars
Suzuki Vitara 4DR 4x2 3 stars
4DR 4x4 3 stars
2001 Light Trucks
Chevrolet S-10 4x2 3 stars
4x4 3 stars
Chevrolet Silverado ExCab 4x2 4 stars
ExCab 4x4 3 stars
Ford F-150 4x4 3 stars
GMC Sierra ExCab 4x2 4 stars
ExCab 4x4 3 stars
GMC Sonoma 4x2 3 stars
4x4 3 stars
Isuzu Hombre 4x2 3 stars
4x4 3 stars
2001 Vans
Honda Odyssey 4 stars
Mazda MPV 3 stars
Chrysler PT Cruiser 4DR 4 stars
For more information, contact www.nhtsa.dot.gov and www.consumerreports.org.
