Newly designed sport utility vehicles are far safer than 2005 models when it comes to rollover risk, according to new federal crash-test results released Tuesday.

Passenger cars, which have much lower centers of gravity, have the lowest rollover risk of any class of vehicle, the National Highway Transportation Safety Administration found. They're followed by pickups, SUVs and vans.

According to the agency, the secret behind the improvement in SUVs is a feature called electronic stability control, now standard for the first time on most models. It detects through sensors when a driver is about to lose control of the vehicle and instantaneously corrects the potential veer by braking on the appropriate wheel. Electronic stability control also prevents the rear end of the vehicle from sliding out when a driver encounters a sharp curve or swerves to avoid an obstacle.

The system costs $600 to $1,800 as an option, depending on the model. The system is standard in 7 of 10 2006 model SUVs . In 2005 models, only 4 in 10 came with it. The safety gain from electronic stability control in terms of saved lives is about equal to that provided by seat belts, auto industry analysts say.

The highway-safety agency, which rates rollover safety using a five-star system, found that 42 percent of 2006 SUVs earned four stars, up from 34 percent in 2005. To win five stars, a vehicle must have a rollover risk of less than 10 percent. Four-star vehicles have risks of 10 percent to 20 percent; three-star vehicles have 20 percent to 30 percent risks.

The Pontiac G6 and Buick Lucerne -- passenger cars that were tested without the new technology -- were the only vehicles tested in 2006 to earn five stars.

The tests included only vehicle models whose designs changed in the 2006 model year.

For complete rollover test results, including for models unchanged from 2005, go to www.safercar.gov.

According to the Insurance Institute for Highway Safety in Arlington, Va., electronic stability control systems reduce the likelihood of single-vehicle crashes by more than 50 percent for SUVs and passenger cars. In 2004, 49 percent of occupant deaths in SUVs involved single-vehicle rollover crashes, according to the insurer group. That compares with 36 percent of occupant deaths in pickups and 19 percent in passenger cars.

"If I were buying an SUV, I'd be sure to buy one that has electronic stability control," said Russ Rader of the institute. "Research is showing that it's very effective in saving lives."

For new 2006 model SUVs, the Chevrolet HHR had the best safety record on this issue with an estimated 14 percent likelihood of rollover in a single-vehicle crash. The 2006 Chrysler Pacifica and Ford Freestyle, both tested in earlier model years, earned scores of 13 percent.

The HHR doesn't come with electronic stability control, even as an option.

"The HHR is much more stable and has a lower center of gravity," said Eric Bolton, a public-affairs specialist for the highway-safety agency. "It has a wide wheel base and it's lower to the ground, almost like a passenger car."

Among new 2006 model pickups, the Honda Ridgeline 4X4 and the Toyota Tacoma 4X2 took top honors with 13 percent rollover ratings. The best van was the Kia Sedona, also with a 13 percent rating.