How do anti-lock braking systems (ABS) work?

The anti-lock braking system (ABS) sits up there with seatbelts and airbags in terms of its widespread adoption in the automotive world. It's one of the most common and essential safety feature in cars.

But did you know ABS is actually quite old in car terms? We’re going to cover the brief history of this defining piece of tech, and how it keeps you safe on the road.

When and how did ABS become popular?

The modern ABS can trace its roots as far back as the early 20th century, with mechanical anti-skid systems for airplanes. ABS aimed to prevent the lock-up of the wheels during hard braking, which extends stopping distances and minimizes steering control.

The first electronic anti-skid system showed up on the Ford Thunderbird in 1969, but it only worked on the rear wheels. It would be two more years before the market saw a four-wheel ABS.

How does it work?

It was 1971’s Chrysler Imperial that offered the first four-corner ABS. Called Sure-Brake, it featured a speed sensor on each wheel and an electronic control box in the trunk. The system doesn’t pump the brakes as a driver would during hard stops: instead, it incrementally releases pressure as it detects lock-up.

This basic premise is how modern ABS work, too. It results in a noticeable pulsing feeling and sound from the brake pedal, which can surprise those unaware of the trait. That’s why it’s recommended to get to know your car’s braking capabilities in a safe environment when you first get it.

Modern ABS are interwoven into a car’s more advanced driver assist systems. In fact, starting in 2012 it technically became mandatory on all new cars sold in Canada. That’s because Transport Canada made electronic stability control (ESC) required on all light-duty vehicles, and ESC requires ABS to function.

Okay, so how does ABS help me?

ABS offers a few key advantages, especially in Canada. For one, it provides more consistent emergency stop distances, since the driver doesn’t have to worry about applying too much brake and locking the wheels. Remember that 1971 Chrysler Imperial? When Popular Science tested it at the time, it found the stopping distances were as much as 40% shorter on slippery surfaces.

There aren’t many countries that see slippery surfaces during more of the calendar than Canada. Winter can be full of nasty surprises on the road, including black ice. ABS can’t stop a slide from starting, but it allows a driver to focus on steering the car while the computer control unit handles the braking.

ABS is also central to another modern car feature: emergency brake assist. On cars so equipped, the computer can detect a potential accident and apply the brakes to avoid it. With ABS, the reaction time and maximum braking potential can be the difference between a crash and a safe stop.