ESC is a vehicle control system comprised of sensors and a microcomputer that continuously monitors how well a vehicle responds to a driver's steering input and selectively applies the vehicle brakes and modulates engine power to keep the vehicle traveling along the path indicated by the steering wheel position. This technology helps prevent the sideways skidding and loss of control that can lead to rollovers. It can help drivers maintain control during emergency maneuvers when their vehicles otherwise might spin out.

See Status Report, Vol. 41, No. 7, June 13, 2006

A driver loses control when the vehicle goes in a direction different from the one indicated by the position of the steering wheel. This typically occurs when a driver tries to turn very hard or to turn on a slippery road. Then the vehicle may understeer or oversteer. When it oversteers it turns more than the driver intended because the rear end is spinning or sliding out. When a vehicle understeers it turns less than the driver intended and continues in a forward direction because the front wheels have insufficient traction. ESC can prevent under- and oversteer by selectively braking wheels to produce a counteracting force which helps correct the vehicle's direction of travel. In some cases engine throttle also is reduced.

See ESC explained

In Institute studies, ESC has been found to reduce fatal single-vehicle crash risk by 56 percent and fatal multiple-vehicle crash risk by 32 percent for cars and SUVs. Many single-vehicle crashes involve rolling over, and ESC effectiveness in preventing rollovers is even more dramatic. It reduces the risk of fatal single-vehicle rollovers by 80 percent for SUVs and by 77 percent for cars. If all vehicles were equipped with ESC, as many as 10,000 fatal crashes could be avoided each year.¹ Federal studies also show large benefits. The National Highway Traffic Safety Administration (NHTSA) estimates the installation of ESC reduces single-vehicle crashes of cars by 26 percent and single-vehicle crashes of SUVs by 48 percent. NHTSA estimates that ESC has the potential to prevent 64 percent of the car rollovers and 85 percent of the SUV rollovers that would otherwise occur in single-vehicle crashes.²

ESC is available on some large trucks and has great potential to prevent rollover crashes, but the benefits of ESC for these vehicles haven't yet been evaluated.

For most drivers ESC isn't likely to activate frequently. It won't prevent most of the fender-bender crashes that occur so often in stop and go traffic, for example. It's designed to help a driver in the relatively rare event of loss of control at high speed or on a slippery road.

Current model vehicles don't have to have the technology but more than half do ahead of a new federal rule that will require ESC in all cars, SUVs, pickups, and minivans by the 2012 model year. Under the final rule NHTSA issued in April 2007, 55 percent of 2009 models, 75 percent of 2010 models, 95 percent of 2011 models, and 100 percent of 2012 models must have ESC.³ Many manufacturers have announced that they will have ESC in all of their passenger vehicles before these deadlines. The government doesn't mandate ESC for large trucks or buses. The Institute requires passenger vehicles to have ESC as one of the criteria needed to earn TOP SAFETY PICK.

Germany's Robert Bosch GmbH was the first supplier to bring ESC to market on the 1995 Mercedes-Benz S-Class in Europe.⁴ The technology made its way to the American market a few years later as optional equipment on luxury cars. By the 2001 model year it was standard on a number of high-selling vehicles and available as an option on many more. Since then automakers have been putting ESC on their vehicles, particularly SUVs, at a steady rate. The systems are marketed under various names, including dynamic stability control, vehicle stability control, dynamic stability and traction control, among others. The percentage of vehicles with this technology has increased tenfold since the 1998 model year. For the 2008 model year, ESC was standard on 63 percent of new passenger vehicle models and optional on 15 percent. ESC was standard on 64 percent of cars, 95 percent of SUVs, and 12 percent of pickups.

Vehicles equipped with electronic stability control

Yes. Losses under collision coverage are about 15 percent lower for vehicles with ESC than for predecessor models without it, according to an analysis by the Highway Loss Data Institute. ESC doesn't have much effect on liability claims filed when an at-fault driver damages someone else's car or property or the frequency of personal injury claims filed to cover medical expenses. These findings track police-reported crashes, which show little effect of ESC on the risk of low-severity multiple-vehicle crashes.⁵