ESC goes by various names including Electronic Stability Program, StabiliTrack, and Active Handling. An extension of antilockbrake technology, ESC helps drivers retain control of their vehicles during high-speed maneuvers or on slippery roads.

How ESC works: Antilock brakes have speed sensors and independent braking capability. ESC adds such sensors as pitch and yaw that continuously monitor how well a vehicle is responding to a driver's steering input. When a driver is about to lose control, ESC automatically applies braking to individual wheels and, in some cases, reduces throttle.

ESC lowers the risk of fatal singlevehicle crashes by more than 56%, and fatal multiple-vehicle crashes by 32%, suggests the study. Many single-vehicle crashes involve rolling over. Here, ESC is especially effective. It reduces the risk of fatal single-vehicle rollovers of SUVs by 80%, and 77% for cars. "The findings indicate that ESC should be standard on all vehicles," says Susan Ferguson, Institute senior vice president for research. "Very few safety technologies show this kind of

large effect in reducing crash deaths." ESC comes standard on 40% of 2006 passenger vehicle models and is optional on another 15%. It's standard on every 2006 Audi, BMW, Infiniti, Mercedes, and Porsche. Cadillac, Jaguar, Land Rover, Lexus, Mini, Toyota, Volkswagen, and Volvo offer at least optional ESC on all of their models. But ESC, standard or optional, is limited to 25% or fewer models from Chevrolet, Dodge, Ford, Hummer, Mazda, Mitsubishi, Saturn, Subaru, and Suzuki. The percentage of SUV models with standard ESC has been growing faster than for cars. As a stand-alone option, ESC costs from about $300 to $800, but can exceed $2,000 on some models when packaged with other equipment.

Results of the Institute's studies also show a correlation between crash risk and insurance losses. According to a recent analysis by the Highway Loss Data Institute, an affiliate of the Insurance Institute for Highway Safety, losses under collision coverage are about 15% lower for vehicles with ESC than for predecessor models without it. However, ESC doesn't have much effect on property damage liability claims or the frequency of injury claims. These findings track policereported crashes, which show little effect of ESC on the risk of lowseverity, multiple-vehicle crashes.