ESC and how it helps drivers maintain control
What is ESC? Electronic stability control, or ESC, uses the speed sensors on each wheel and the ability to brake individual wheels that are the basis of antilock brakes. ESC adds a control unit that monitors steering wheel angle and vehicle rotation around the vehicle's vertical axis. This unit uses the steering and rotation information to detect that the vehicle is about to travel in a direction different from the one indicated by the steering wheel position. Then ESC automatically brakes the appropriate wheel to help the driver maintain control. In many cases engine power also is reduced.
How ESC helps drivers maintain control: 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 (swerve) or to turn on a slippery road. Then the vehicle may understeer or oversteer.
When a vehicle understeers it turns less than the driver intended and continues in a forward direction because the front wheels have insufficient traction. When it oversteers it turns more than the driver intended because the rear end is spinning or sliding out. ESC can prevent understeering and oversteering by briefly braking the appropriate wheel. In many cases engine power also is reduced.