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What is Traction Control?

By Autolist Staff | February 8, 2019

Traction control is a computer-controlled system on your vehicle that monitors wheel slippage. If it detects one wheel is spinning faster than the others, the system will automatically apply the ABS to that wheel or it will cut engine power to that wheel. Unlike electronic stability control, automakers aren't required by law to include traction control in their vehicles, though most do on nearly all models they sell.

What Is Traction Control?

If you've ever felt your vehicle slide while it's going around a corner or noticed your tires spinning under throttle from a full stop, you've experienced a loss of traction. It's a common phenomenon in nearly any type of vehicle in inclement weather (snow, sleet, rain and ice) or on surfaces like loose gravel or mud.

Many modern vehicles are equipped with traction control to restore traction in these conditions. Its purpose is to give vehicles traction on roads or low-friction surfaces where the tires may have trouble finding a grip.

For example, when a vehicle without traction control tries to move from a dead stop on a slippery surface such as a snowy road, loose gravel or ice, its tires may spin. This keeps the vehicle from moving forward. Or if the vehicle is in motion, wheel slip can create a dangerous slide or loss of control.

A traction control system monitors if any wheel is spinning faster the others; if so, the system will either use that wheel's ABS to prevent slippage or it will cut the engine's power to that wheel.

The important thing to remember is that traction control cannot create traction when there is none to begin with, such as on a sheet of ice.

How Does Traction Control Work?

Traction control is different than all-wheel-drive or four-wheel-drive systems, which change which wheels it sends drive power to.

Traction control functions a lot more like anti-lock braking systems. In such a system, the vehicle is equipped with wheel speed sensors that send information to an electronic control unit, which then instructs a hydraulic modulator to pump the brakes. The ECU keeps tabs on how the wheels are spinning and if it detects one spinning faster than the others, it activates the hydraulic modulator to pump the brakes to reduce the spinning. In some traction control systems, the ECU also reduces engine power to these wheels, which is likely causing the spinning in the first place. When the wheel regains traction, the ECU continues to monitor wheel rotation compared to the other wheels.

When Is Traction Control Helpful?

Wet, icy, snowy, uneven, loose or soft surfaces are difficult for many vehicles to navigate because there is a low amount of friction between the surface and the tires. Traction control systems prevent vehicles' wheels from slipping in conditions in which they might otherwise spin out.

For example, a vehicle attempting to start from a dead stop on a steep gravel road may spin its tires relentlessly without traction control. But such a system would limit the spinning of the wheels without traction and allow the wheels with traction to move the vehicle.

Another example is driving in snowy conditions where the tires hit a thick patch of slush and lose traction, which causes the vehicle to slow down or slide. Traction control would apply the brakes to correct the vehicle's trajectory.

Is Traction Control Effective?

Many tests do show a correlation between traction control systems and reduced wheel slip on surfaces with low friction. However, the effect is more pronounced on four-wheel-drive vehicles than those with front-wheel-drive.

Tests also show that traction control systems that reduce engine power to spinning wheels are more effective than brake-only systems in terms of stability. On the other hand, brake-only systems do appear to improve acceleration.

It's important to remember that traction control does not affect the vehicle's ability to slow or stop in the event of a loss of control and potential crash; in short, it doesn't prevent crashes.

However, when bundled together with ABS and electronic stability control, these systems can reduce fatal accident risk by as much as 50 percent.

When Is Traction Control Not Effective?

As with many other vehicle safety features, traction control does have limitations. Drivers should not treat traction control as a failsafe for their bad or reckless driving habits or driving in particularly bad road conditions.

Speeding, following too closely behind the vehicle in front of you and aggressively swerving in and out of lanes work against traction control, not with it. Driving too fast or too aggressively for inclement road conditions increases the risk of a crash; traction control is not designed to prevent this.

Traction control systems are also not designed to reduce stopping distances, and it might actually allow vehicles to reach higher speeds than they would normally on slippery roads.

Drivers should take the same precautions in adverse conditions with traction control as they would without it. It's best to think of traction control as a safety net that can help you when even normal safe driving procedures are not enough.

When Do You Turn Traction Control Off?

Sometimes it can be useful to turn traction control off. If your vehicle is stuck in snow and you need the wheels to spin to gain traction, it can be useful to turn off the system to allow the wheels to slip (remember that traction control is designed to prevent this kind of slipping). Turning off traction control and starting the vehicle in second gear can sometimes be an effective way to get the vehicle moving again.

How Did Traction Control Start?

The modern traction control system has its roots in a few other vehicle systems. Technically, ABS or anti-lock brake systems are also a type of traction control. ABS keeps your brakes from locking up in an emergency braking situation, which helps keep your car in control and not sliding as a locked-brake vehicle would.

Another feature with traction-enhancing abilities is the limited slip differential. The LSD sends power to both drive wheels vs. an open slip differential, which sends power to only one wheel. Again, two wheels receiving power vs. only one helps keep your car on the road.

Traction control systems can usually be disabled via a button on the dashboard or in a vehicle's settings menu, but the best course of action is to drive safely and let them function as a back-up.

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