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What is ABS or an anti-lock braking system?

Today, Australian Design Rules mandate ABS be fitted to all new cars sold in Australia. (image credit: valourdigest.com)
Iain Kelly
Contributing Journalist
CarsGuide

4 Sep 2018 • 3 min read

Thirty years ago, if you had to suddenly avoid an accident (if an animal ran out on the road, for example, or a car jumped a red light) it was a terrifying test of driving skill that required something called threshold braking.

This is the act of braking as hard as possible, but without pressing too hard on the brakes and locking a wheel, which could send you into a slide and possibly into a crash. Alternatively, you might have had to pump the brakes on a slippery road, a practice known as cadence braking.

Thankfully, the invention of ABS has made these practices mostly redundant. But what does ABS stand for? Those three letters are a contraction of Anti-lock Braking System (otherwise known as Anti-Lock Brakes, or sometimes ABS brakes).

But what is ABS, and how does ABS work?

While the technology continues to advance, the basic premise is that an anti-lock braking system can sense individual wheel speeds, which means it knows when one wheel has stopped spinning. That means that wheel has locked and the brakes are no longer effective at stopping the car.

The ABS system then releases the brake pressure on that wheel, then quickly reapplies it, continuing that rapid-fire cycle over and over until the car is stopped. This can be felt by the driver, as the brake pedal pulses or shudders under their feet if you stand on the brakes as hard as possible while driving down the road.

ABS systems use a tone ring (or reluctor wheel) attached to part of the car that turns in time with the wheels, with a magnetic speed sensor used to ascertain wheel speed. It passes the information on to an electronic control unit, which runs the ABS system through a distribution block and pump which modulates individual brake calipers.

Amazingly, engineers have worked on ABS-style systems since 1908, though the first car fitted with ABS was the 1966 Jensen FF. While Chrysler, Nissan, Toyota, Cadillac, Ford and Oldsmobile all had ABS options from 1971, it was the '78 Mercedes-Benz W116 model which introduced an electronic, multi-channel ABS system from Bosch that most closely resembles a modern set-up.

Today, Australian Design Rules mandate ABS be fitted to all new cars sold in Australia, meaning this life-saving technology is available not only for all new car-buyers, but a large proportion of second-hand buyers, too.

Is ABS the single most important automotive safety invention? Tell us in the comments below.