What is an Anti-Lock Brake System? How ABS Improves Car Safety

Anti-lock brakes have been around since 1978 or maybe even earlier in the ‘70s, and have since become a standard safety feature on nearly every car since the ‘90s, roughly. Before and without ABS, drivers had to “pump the brakes” when they lost traction. That means pressing the pedal and lifting off repeatedly.

The reason is to release the brake pressure so the wheel stops skidding — locked in place and sliding — and starts rolling again, so it can start rolling slower, bringing the car to a controlled stop. As electronics and advanced braking systems, like disc brakes replacing drums, came to the car market, engineers found a way to replicate this action using:

• Electronic speed sensors
• Pressure regulating valves
• Quick-acting hydraulic pumps
• Electronic controllers

From initial systems that managed to give a little control back and maybe avoid an accident, ABS systems are now seamlessly integrated as part of modern safety suites. Advancements in every component make them work faster, smarter, better, and less noticeably.

ABS works by pumping the brakes very quickly and repeatedly, creating almost a shuddering or chattering effect of roll-and-slip rather than a full-on, out-of-control slide. It can be rather effective in helping the car’s wheels re-establish good traction with the road surface to slow down and avoid an accident.

Here’s how ABS works:

1. Constant monitoring: Speed sensors continuously track the rotational speed of each wheel.
2. Braking initiated: The driver presses the brake pedal to slow down the vehicle.
3. Potential skid detected: On a slippery surface or due to low-traction factors (like bald tires or wet roads), one or more wheels begin slowing down too quickly, risking lock-up.
4. ABS engages: The system detects the imbalance and reduces brake pressure to the whole system using its valves, potentially reducing the chance of a skid.
5. Brake pressure adjusted: The ABS rapidly alternates between reducing and increasing brake pressure — essentially “pumping the brakes” faster than a human could (dozens of times per second).
6. Regaining traction: The wheel starts rolling again, maintaining grip on the road.
7. Driver stays in control: Instead of skidding uncontrollably, the vehicle remains steerable, allowing the driver to avoid obstacles and brake safely.

Critically, the driver will still feel — and be — in control and able to steer properly to potentially avoid an accident. One of the most common ABS scenarios is during a panic stop. When you slam on the brakes, a car without ABS will lock up the wheels and screech, skid, and slide, often leaving rubber marks on the road. A skidding wheel can’t change direction, hence the risk of an accident.

But with ABS engaged during a panic stop, any wheel that’s about to skid has its brake pressure reduced so it can grab traction again. Then it’s quickly reapplied to the wheel to slow it down some more. When this happens ten or twenty times a second, the wheel can regain traction and slow, steer, or stop the vehicle effectively.

You might feel it apply to one wheel when you bounce over a pothole or hit a slick oil spot. Or ABS might hit all four wheels during a panic stop or when the whole road is slick with ice, snow, or rain.

The goal of ABS is to reduce the chance of wheel skid, which reduces the car’s ability to turn and stop — since any turning motion is overcome by the direction of the skid. While ABS isn’t a guarantee, it can help:

• Reduce stopping distance
• Keep the driver in control
• Avoid a spinout— when the back wheels keep going, but the front wheels don’t, and the car tries to overtake itself, leading to a drift or tailspin scenario
• Maintain traction and speed down a hill — when slippery surfaces combine with gravity to make the car go faster than intended

There are two scenarios when you might be driving without an ABS to help control skids:

1. You’re driving a car that didn’t come with anti-lock brakes, usually something from the 1980s or before
2. The ABS is present, but broken or faulty

If you’re in an old car, you’ll need to remember to pump the brakes. Aside from upgrading the braking system, that’s the best way to regain control in a skid situation.

On a vehicle with a broken ABS, well, getting it fixed is the safest move. Pumping the brakes is the backup option since this method will still be somewhat effective on modern vehicles. Modern cars are a lot heavier than they used to be, so even while tires and other features have improved, they still may take longer to stop without ABS.

Canada also mandated a more advanced evolution of ABS called ESC, or electronic stability control. ESC goes even further than ABS alone, monitoring steering wheel input to know if a certain wheel is needed for turning force. With an ESC system, the ABS can be applied only to certain wheels instead of the whole braking system.

The goal of ESC is to use the ABS and other components to keep the car from swerving out of control. By bringing down the speed of a certain wheel, it can actually change the direction of the car. As it slows down that wheel, the car is pulled in that direction, ideally back in a straight line.

While ABS will help you slow down and avoid a skid, ESC will also help calm down a vehicle that’s swerving, tipping, or otherwise losing directional control. Combined, they make for a powerful safety measure keeping drivers — and anyone else around — a bit safer.

ABS has also spawned features like traction control and emergency braking, to name some other common safety features and driving aids. As technology advances, it uses better sensors, computers, and other elements like AI-powered algorithms to detect and react to skids even sooner, quicker, and less noticeably.

Today’s safety technology uses these systems plus a bounty of modern sensors and computers as part of advanced safety suites. Explore how Mitsubishi’s All-Wheel Control and Super-All Wheel Control systems use ABS, among a host of other smart components, to offer driving modes, safety improvements, and performance gains.