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Electronic stability control (ESC)

What it is, how it works

By

General Motors Stabilitrak in action

Electronic stability control helps keep drivers from losing control under adverse conditions -- even in poor-handling vehicles like SUVs and pickups

Photo © General Motors

What is electronic stability control?

Electronic stability control (ESC) is a safety feature that detects and prevents (or recovers from) skids. ESC can help keep the driver from losing control of the car in a panic swerve or when driving on slippery roads.

Why is electronic stability control important?

A government study showed that ESC reduced single-vehicle crashes by 34% for cars and 59% for SUVs. The Insurance Institute for Highway Safety estimates that ESC reduces the risk of fatal single-vehicle wrecks by 56% and fatal multiple-vehicle crashes by 32%. Because of its proven effectiveness, the US Government has mandated that all new cars must be equipped with ESC by the 2012 model year.

How does electronic stability control work?

ESC uses sensors in the car (wheel speed sensors, steering wheel position sensors, yaw sensors, etc.) to determine which direction the driver wants the car to go, and compares that to which way the car is actually going. If the system senses that a skid is imminent or has already started -- in other words, that the car is not going in the direction the driver is telling it to go -- it can apply the brakes on individual wheels to bring the car back under control. Because the system can brake individual wheels, whereas the driver can only brake all four wheels at once, ESC can recover from skids that a human driver can't.

Is electronic stability control the same thing as traction control?

No. Traction control senses wheelslip (the drive wheels breaking loose and spinning) and reduces engine power or applies the brakes to stop it. Traction control can prevent some types of skids, but it does not provide the same level of protection as ESC. ESC programs have a traction control function, so while ESC can do the same job as traction control, traction control cannot do the same job as ESC.

If my car has electronic stability control, does that mean I can't lose control of my car?

NO! Even with ESC, it is still possible to lose control of the car. Excessive speed, slick roads, and excessively worn or improperly inflated tires are all factors that can reduce ESC's effectiveness.

How do I know when my car's electronic stability control system is active?

Every manufacturers' ESC system works a little differently. With some systems, you may feel the car change direction slightly or hear the chattering of the antilock brake system. Other systems apply so gently as to be nearly imperceptible. Most ESC systems have a warning light that flashes when the system is active; some, including most Toyota and Lexus cars, have a beeper that sounds. ESC is most likely to activate on slippery (wet, snowy or icy) roads, though driving quickly on curvy, hilly roads or hitting a bump while cornering may also trip the ESC system. Some performance-oriented systems will allow a skid to develop before stepping in (see below).

What are performance stability control programs?

Some high-performance cars have ESC systems that are programmed to be more permissive, allowing the car exceed its limits of traction and actually skid a bit before the system steps in and recovers from the skid.

What are some other names for electronic stability control?

Different manufacturers use different names for their electronic stability control systems. Among them:

  • Electronic Stability Program (ESP)
  • StabiliTrak
  • Vehicle Stability Assist (VSA)
  • Vehicle Stability Control (VSC)
  • Vehicle Dynamic Control (VDC)
  • Dynamic Stability Control (DSC)
  • AdvanceTrac with Roll Stability Control
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