What does ABS mean on a car? Understanding anti-lock braking system

There are a lot of opaque initialisms associated with cars that can be confusing when you see them on a spec sheet or a badge right on the vehicle. One such example is ABS, which has nothing to do with a gym rat's six-pack. ABS stands for anti-lock brake system or anti-lock braking system. It describes an automatic feature that senses when a wheel is about to lock up and then reduces brake pressure at that wheel briefly to prevent it. You may have noticed the ABS light flashing or lighting up solid on your dashboard, which can mean a few different things.

How ABS works

Before ABS, new drivers were taught to "pump the brakes" in situations where the wheels are likely to lock up, such as when driving on a wet or icy road. A wheel will lock up when the tire mounted to it exceeds its available grip under braking. This can send the vehicle into a skid. To prevent that undesirable outcome, drivers were taught to pulse brake pressure, giving the tires a chance to regain traction before attempting to slow the vehicle again.

Anti-lock brakes made that pumping a thing of the past. Using sensors at the wheels, the control electronics can sense when a lockup is imminent and very briefly release the pressure to the system, usually only to the specific wheel in question. This manifests in a quick pulsating noise and some vibration in the brake pedal. Although these can be unsettling sensations, it's important for drivers of an ABS-equipped vehicle to know that they should keep their foot planted on the stop pedal, allowing the system to handle the pumping. ABS can pump the brakes more quickly and precisely than any human.

It's a good idea for new drivers to experience this feedback in a safe environment; an empty, rain-soaked parking lot is a good option. Just get up to speed and then press firmly on the brake pedal until the car comes to a full stop. Hopefully when the system comes on in a real emergency the driver will trust it to do its job instead of backing off of the pedal.

What does it mean when the ABS light appears on my dashboard?

When ABS is active, the indicator light on your dashboard will flash quickly to let you know it's working. If you see the ABS light constantly illuminated, however, it's a signal that something's wrong. Depending on the problem and the vehicle, this could mean that ABS is not working or is working at reduced capacity. Potential causes include problems with the wheel sensors, an issue with the electro-hydraulic ABS pump, or something amiss within the ABS control module.

If you see this light on your dash, it's time to pull out your owner's manual to see what to do. In most cases, you'll want to drive the vehicle as if ABS isn't functioning – which means leaving extra space between your car and the one ahead to account for longer stoping distances and manually pumping the brakes any time you sense a lockup – and get the car to a mechanic to address and rectify the problem.

ABS used to be a novelty

Automotive anti-lock brakes were first offered on the 1966 Jensen FF, followed closely by systems offered by Ford (Sure-Track in 1969) and General Motors (Track Master in 1971). All of those early systems acted only on the rear wheels; the first car to offer four-wheel ABS was the 1971 Chrysler Imperial with the Sure Brake system. Although it's often credited with pioneering anti-lock braking systems, Mercedes-Benz didn't roll out its version until the 1978 S-Class. The Mercedes system was the first to use digital control, however.

When anti-lock braking systems first showed up on the market, manufacturers often put a small badge on the car (usually on a front fender or somewhere on the rear) to tell folks that it was equipped with this new safety system. As the technology became more prevalent, such telltales went away.

The feature began proliferating throughout the market in the 1980s, and by the '90s it was at least available on most models. The U.S. government mandated the inclusion of ABS along with electronic stability control in 2012 as part of FMVSS 126. Any vehicle produced to be sold in the U.S. from September of that year required the system be included as standard equipment.

Today, anti-lock brakes are becoming commonplace on motorcycles, and many safety advocates are pushing for the system to be mandated on two-wheelers. Automatic emergency braking, a safety system that relies one ABS to slow a vehicle in the event of an impending collision, will be required on vehicles produced for U.S. sale from September 2029.

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