Traction control: How does it work?

Everybody makes mistakes once in a while, so it’s reassuring to know that car manufacturers accept that we’re all human.

To this end, a series of foolproof systems are fitted to modern vehicles which try their best to get us out of trouble when we’ve suffered from a temporary bout of brain fade.

Traction control is one of the more popular systems, and here we explain what exactly it does (other than quietly tutting at our occasional lapses.)

Slip ‘n’ slide

We’re sure many of you may have occasionally experienced wheelspin, particularly when driving in slippery conditions, and usually when pulling out of junctions. Wheelspin occurs when the turning force (or torque) applied to the driven wheels exceeds the level of friction between the tyres and the road surface.

When driving a front-wheel-drive car (including the Ford Focus and Volkswagen Golf) around a corner, wheelspin will reduce grip at the front of the car, causing it to slide outwards from the intended line. This is known as understeer. Wheelspin in a rear-wheel drive car (like most BMWs and Jaguars) will cause oversteer – the back wheels try to travel faster than the fronts, causing the car’s desire to spin. Traction control limits both of these situations before they get too far out of hand.

The Ferrari 458 Speciale has a highly advanced Traction Control System

How does it achieve this?

As mentioned in our ABS feature, modern cars are fitted with speed sensors in every wheel, and when a difference in speed is noted in one, the brakes can be applied accordingly. The same sensors can be used to detect if one or more wheels are spinning to a different rate to road speeds.

In other words, if you accelerate too quickly for the road conditions and induce wheelspin, the traction control system will either gently apply the brakes or even cut power from the engine to bring everything back into line. Traction control systems react so quickly on modern cars, that save for a flickering light on the dashboard when they cut in, only keen drivers will notice that anything has happened.

Anything else I need to know?

Nearly every modern car will be fitted with a traction control system of some sort. Performance models often have the option to turn it off – this is because when driving on, say, a track day, the quickest way around a lap is by allowing some slip, which often traction control limits. However, modern versions are so advanced on these sorts of cars that they are even able to allow a little leeway before intervening.

Supercar makers like Ferrari have started to include a traction control setting that allows you to slide the car around slightly, but with the computer keeping an eye on things should you obviously be about to lose control.

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