Traction control and Electronic Stability Control systems, on current production vehicles, are typically (but not necessarily) electro-hydraulic systems designed to prevent loss of control when excessive throttle or steering is applied by the driver.
The intervention can consist of any, or all, of the following:
- Retard or suppress the spark to one or more cylinders
- Reduce fuel supply to one or more cylinders
- Brake one or more wheels
- Close the throttle, if the vehicle is fitted with drive by wire throttle.
The brake actuator, and the wheel speed sensors, are the same as that used for Anti-lock braking system.
Traction Control is usually considered as a performance enhancement, allowing maximum traction under acceleration without wheel spin. It is also extremely useful in countries that suffer from icy or snowy roads: When driving up a slippery hill, giving full gas and letting the car's TCS take care of the throttle control will allow to scale slopes that are nigh-on impossible without TCS.
It is particularly advantageous to 4x4 vehicles when driven off road on a loose surface. Conversely Vehicle Stability Control is considered a safety feature preventing operation of a vehicle at the edge of the safety envelope.
It is widely thought that TC removes some skill and control from the driver. As such it is unpopular with many motorsports fans. Some motorsports series have given up trying to outlaw traction control, either because the general function is so hard to detect, eg F1, or, as in many U.S. stock car series, because it is possible to incorporate an effective traction control device in the wiring, invisible to scrutineers.