The anti-lock brake system (ABS) is a safety system that allows the wheels on a motor vehicle to maintain tractive contact / friction with the road surface no matter how hard the driver pushes the brake pedal. The ABS does this by preventing the wheels from locking up (stopping rotation). This is important because when the wheels on your car lock up, you can go into an uncontrollable skid.  As such, the ABS generally offers improved vehicle control and decreases stopping distances on both dry and slippery surfaces by allowing drivers to brake and steer at the same time thereby avoiding an accident.  The video below provides a good demonstration of the concept.

Since initial widespread use in production cars, anti-lock braking systems have evolved considerably. Recent versions not only prevent wheel lock when braking, but also electronically control the front-to-rear brake bias. This, coupled with stability control systems, can improve the handling performance on high speed cornering.

It is a good idea to check out how your ABS feels by braking hard on gravel under safe conditions, and if possible with a skilled trainer.

The ABS works by monitoring each wheel with a wheel speed sensor to see when it locks up. As soon as lockup is detected then the hydraulic pressure to the brake on that wheel is released, unlocking the wheel and allowing it to rotate again. All this happens very rapidly and the driver only knows it is going on by a sight brake feel change and a noise.

Maintaining Your ABS
The ABS system is very reliable if the brake fluid is changed (via a brake fluid flush) at regular intervals. Neglect can lead to very expensive repairs. The electronic controlled activator and computer is a very expensive unit ($1300 or more).

The Brake Fluid Flush
A brake fluid flush is a service that is performed when the brakes are serviced (i.e. when brake pads replaced). If the brakes have lasted over 3 years or 50,000 miles (whichever comes first) then the brake fluid should be flushed as a separate service. This job takes from half an hour to an hour to perform and should include cleaning the brake fluid reservoir. The cost is from $75 to $150. It involves either using pressure to push out the fluid through the vehicles four bleed fittings or by using the vehicle’s master cylinder to pump out the old fluid until it is coming out clean.

What This Means for You
In closing, the ABS is a safety system that enhances the controllability of your vehicle under hard braking conditions.  It should last for quite a while as long as it is properly maintained via regularly scheduled brake fluid flushes. Importantly, nothing replaces safe driving habits, so be sure to maintain a safe driving distance, and remember to increase your stopping distances on wet or slippery roads (rain, ice, snow) or road surfaces covered with loose materials like gravel.