What is ABS?

Maximum braking without loss of control: how ABS helps you steer out of trouble and stay safe

Chris Rosamond
Sep 2, 2021

There are plenty of acronyms and initialisms knocking around in the world of cars, and even we have to think twice when some of the more obscure ones are rolled out in car ads and promotions.

One of those which has been around the longest is ABS, which is an initialism because you say it by pronouncing each letter in turn. (If you start talking about your ‘abs’, don’t be surprised if people start gazing at your belly instead of pondering your braking system.)

ABS stands for Anti-lock Braking System, which is a feature fitted universally to new cars. In fact, it has been a legal requirement since 2004, so if your car hasn’t got it you probably are overdue for an upgrade.

The system has been around far longer than that and was used on aircraft including Concorde in the 1960s to reduce stopping distances on slippery runways. It clearly took a while to become mainstream in cars, although manufacturers are often proud to trumpet their leadership in safety matters.

How does ABS work?

When you press the brake pedal hard in an emergency on a car without ABS, especially on a wet or icy road, a lack of care or skill means you’ve a very good chance that the brakes will lock the wheels up. A wheel into one position instead of rotating will have no option but to skid as the car’s momentum carries it forward. Skidding means a total loss of grip, and no grip means you’ve lost control of steering and braking. In such scenarios the car could end up anywhere, and before the advent of ABS that frequently meant the nearest hedge or, even worse, piling into oncoming traffic.

As stated on the tin, ABS stops a car's brakes from locking. So even if you're forced to slam your foot on the brake pedal and perform an emergency stop, you will be able to retain control and avoid spearing off into the nearest hazard.

The main component of an ABS system is a computer called a controller, which monitors data from sensors positioned at each wheel. The sensors record how quickly a wheel is rotating.

The moment that the controller detects a wheel starting to skid, it releases the brakes for a split second until the wheel regains grip. It then slams the brakes on again.

As the wheel loses grip for a second time, the process is repeated and this continues at a rate of up to 15 times a second. It slows the car down quickly but maintains grip so you can steer out of trouble at the same time.

When ABS is active, there's an odd sensation from the brake pedal, and it feels as if it's jerking or vibrating. But you've got to keep your foot hard on the brake to stop in the shortest distance. When the system is in use, an ABS light will usually flash on the dashboard too.

 

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