Traction Control System

Automotive illustrated glossary

Toyota Highlander with four-wheel traction control

A Vehicle Traction Control system helps to maintain wheel traction during acceleration, particularly on slippery roads. It does that by individually applying brake to a slipping drive wheel and reducing the engine torque.
Traction Control System design may vary from manufacturer to manufacturer, but the purpose remains the same - to help the driver maintain control during acceleration by reducing wheel slip and maintaining traction of all drive wheels.
Let's see how the Electronic Traction Control System works on the example with typical front-wheel drive car (In a front-wheel drive vehicle the engine power is sent to the front wheels, so the front wheels are the drive wheels).
Imagine you are accelerating from a stop on an icy road in a front-wheel drive vehicle without Traction Control. If you accelerate very gently, you might be OK, but if you press the gas pedal just a little bit harder, one or both front wheels could lose traction and begin to spin and the vehicle would be very hard to control.
The Traction Control is designed to help in situations like this. Once the Traction Control senses that any of drive wheels start slipping, it reduces the engine torque and slightly applies the brake to that slipping wheel(s) to slow it down just enough to regain traction with the road thus helping you to control your vehicle during acceleration.

Essential to know:
- Traction Control, as any other technology can only do so much. Good driving skills are essential to be safe on the road. Further, Traction Control cannot help in all possible situations; for example, sometimes when a car is stuck in loose, wet snow it might be easier to free it out by turning the Traction Control OFF and letting the wheels to spin to cut through the snow for better grip.
- Proper tires are also important for the Traction Control to be effective.
- The design and operation may vary - check your owner's manual to know what type of Traction Control System you have in your car.

How the actual Traction Control System works
Typical Traction Control system is based on vehicle's Anti-lock braking system (ABS) and uses many of ABS components. It utilizes the ABS wheel speed sensors to monitor the speed of all four wheels. When Traction Control system senses that one of the wheels looses traction (begins to rotate faster) during acceleration, it applies the brakes to that wheel using the ABS hydraulic module and commands the engine control unit to reduce the engine power. When Traction Control system operates, you would probably feel that the engine power is reduced and hear some buzzing noise similar to that of ABS. The Traction Control light may also flash.