How Does Traction Control Work?

Traction Control Systems Are ABS Evolved

Traction control is a car safety feature that's designed to help the wheels of your car grip low-traction surfaces like rain-slick roads. When the tires start to slip, the traction control system kicks in, and the driver is able to maintain control of their vehicle. If a vehicle without traction control attempts to accelerate under those same circumstances, the wheels may slip. The vehicle will then fail to accelerate, and may move unpredictably to the left or right as the wheels are no longer gripping the road.

To accomplish the goal of reducing tire slippage, traction control systems use electronic sensors in a similar manner to more familiar anti-lock brake (ABS) systems. They can also use electronic sensors and controls to limit the amount of power delivery that's available to the driver when road conditions are dangerous.

Traction control systems cannot create traction where there is none, they can only improve existing traction. On nearly friction-less surfaces, like ice, traction control will not help.

What is Traction Control?

If you’ve ever been in a car that skidded out during heavy acceleration, it probably wasn’t equipped with a functioning traction control system (TCS). In the same way that ABS is designed to prevent skids during braking, traction control is meant to prevent skids during acceleration. These systems are essentially two sides of the same coin, and they even share a number of components.

A vehicle with traction control driving on a slick surface.
 Mint Images / Getty

Traction control has grown increasingly common in recent years, but the technology is a relatively recent innovation. Prior to the invention of electronic traction control, there were a number of precursor technologies.

The first attempts at creating traction control systems were made during the 1930s. These early systems were referred to as limited-slip differentials because all of the hardware was located in the differential. There were no electronic components involved, so these systems had to sense a lack of traction and transfer power mechanically.

During the 1970s, General Motors produced some of the first electronic traction control systems. These systems were capable of modulating engine power when a lack of traction was sensed, but they were notoriously unreliable.

Electronic stability control, a related technology, is now required equipment in cars sold in the United States and the European Union. Since many electronic stability systems include traction control, these regulations mean that it is increasingly likely that your next car will have traction control.

How Does Traction Control Work?

Traction control systems function sort of like reverse anti-lock brake systems. They use the same sensors to determine whether any of the wheels have lost traction, but these systems look for wheel slippage during acceleration instead of deceleration.

If a traction control system determines that a wheel is slipping, it can take a number of corrective actions. If a wheel needs to be slowed down, the TCS is capable of pulsing the brakes just like the ABS can.

However, traction control systems are also capable of exerting some management over engine operations. If it’s necessary, the TCS can often reduce the supply of fuel or spark to one or more cylinders. In vehicles that use drive by wire throttle, the TCS can also close the throttle to reduce engine power.

What is the Benefit of Traction Control?

In order to retain control of your vehicle, it’s vital that all four wheels maintain traction. If they break loose during acceleration, the vehicle can go into a slide that you may not be able to recover from.

Under those circumstances, you’re forced to either wait for the vehicle to regain traction with the road or to ease off of the accelerator. Those methods work, but a TCS has a much more granular level of control over engine and brake operations.

Traction control isn’t an excuse for careless driving, but it does provide an extra layer of protection. If you frequently drive in wet or icy conditions, traction control can really come in handy.

Rapid acceleration is sometimes necessary when merging with freeway traffic, crossing busy roads, and in other situations where spinning out could result in an accident. When you absolutely need that kind of rapid acceleration, traction control is extremely useful.

Does Traction Control Always Help?

Traction control systems are great if you’re driving on a road that’s wet or icy, but they do have limitations. If your vehicle is completely stopped on slick ice or in heavy snow, traction control will most likely be useless.

These systems can send an appropriate amount of power to each wheel, but that won’t help if all of your wheels are freewheeling. In those circumstances, you’ll need to provide the wheels with something they can actually grip.

In addition to providing assistance during acceleration, traction control systems can also help you maintain control while cornering. If you take a turn too fast, your drive wheels will tend to lose traction with the road surface.

Depending on whether you have a front or rear wheel drive vehicle, that can result in either oversteer or understeer. If your vehicle is equipped with TCS, the drive wheels stand a better chance of maintaining traction.

When Is Traction Control Helpful, and How Do You Use It?

Traction control isn't really something you have to think about using. When it's needed, it kicks in. Your vehicle may have an option to turn traction control on or off, in which case you'll want to make sure it's on if there's a chance you will be driving in any situation where reduced traction is likely.

Here are some common situations where traction control helps:

  • Trying to start from a stop, or accelerate, when a light rain has caused the road surface to become very slick. Without traction control, your tires could slip, causing your vehicle to lurch in an unexpected direction instead of accelerating.
  • Attempting to accelerate when driving up an incline with an unpaved road surface. Without traction control, your tires could slip, causing you to lose forward momentum. Your vehicle may then slide back down the hill, or even end up sideways.
  • Starting from a complete stop on an icy road at a traffic light with vehicles approaching from behind. Without traction control, the approaching vehicles may overtake you as your wheels slip. On the icy roadway, they may then be unable to stop and hit your vehicle.

In each of these cases, there is some traction with the road surface, so the traction control system is able to leverage that to help you start moving or keep you moving.

Is It Safe to Drive with the TCS Light On?

In most circumstances, an illuminated TCS light means that the system isn’t functioning. That means you won’t be able to rely on it if you find yourself in a bad situation on slick roads. It’s usually safe to drive the vehicle, but you’ll have to pay closer attention to how quickly you accelerate.

Depending on your vehicle, the TCS light may also illuminate whenever the system goes into action. In those cases, it will usually shut off when traction is restored. Since traction control systems usually operate transparently, the illumination of that little light may be the only hint that you were ever in danger of spinning out.