What Is an Anti-Lock Braking System?

ABS stands for Anti-lock Braking System, a key safety feature in most modern cars and trucks. Anti-lock brakes work with a car’s regular brake system by automatically pumping them in the event of a sudden stop.

What Is an Anti-Lock Braking System?

Anti-lock braking systems (ABS) help you steer in emergencies by restoring traction to your tires. Helps prevent wheels from locking up – possibly allowing the driver to steer to safety. May not shorten stopping distance; pedal may vibrate or push back – that’s normal.

ABS stands for anti-lock braking system. It is a safety feature that prevents wheels from locking up while braking to avoid skidding.

ABS consists of computer sensors and solenoid valves which monitor wheel speed. The ABS senses when wheels are about to lock during an emergency braking situation and releases enough brake force to maintain traction with the road surface.

The ABS allows drivers to retain more control of the vehicle by modifying brake pressure.

Without the ABS, drivers can lose steering control of their vehicles while skidding and potentially overturn. ABS is particularly important for controlling wheel speed on loose gravel or slippery surfaces.

However, ABS doesn’t necessarily shorten a vehicle’s stopping distance. On most surfaces, a vehicle equipped with ABS will likely stop faster than one without. But on slippery surfaces, ABS activated by hard braking may increase stopping distance while allowing drivers to keep steering control.

Related: What is Brake?

When Was ABS Invented?

Anti-lock brakes were first tested on railway cars and aircraft in the 1950s. Around this time, the braking system was also implemented on motorcycle prototypes to help prevent skidding and loss of traction.

By the 1960s, the system was used on the world’s first four-wheel drive Formula One car. From here, Daimler and Mercedes-Benz began working on a system that could be applied to cars. After much trial and error, Mercedes-Benz revealed the technology at a Daimler test track in 1978.

From then on, anti-lock braking systems were implemented in more and more cars. Today, it’s a standard in almost all cars and it’s safe to say ABS has greatly improved the safety of the roads we drive on.

How does the Anti-Lock Braking System work?

When making a sudden stop, it is possible that one or more of your vehicle’s wheels could lock up, leaving you with little control of your vehicle.

During wheel lock, the wheels of your vehicle stop rotating, causing your car to slide. For years, drivers were taught to pump the brakes when they felt their vehicle steering into a skid.

Today, ABS technology automates the brake pumping process so you can concentrate on steering the vehicle to safety during an emergency situation. By preventing your car’s wheels from locking, anti-lock brakes ensure that you are able to steer during a hard braking event.

In an anti-lock braking system, your car’s wheel speed is monitored and if wheel lock is detected, a sensor sends a message to a controller that releases and applies the brake up to 20 times per second, preventing a lock up and helping you maintain control of your vehicle.

In many of today’s newer cars and trucks, anti-lock brakes work in conjunction with other safety systems like traction control and electronic stability control to deliver a safer driving experience.

Parts Of Anti-Lock Brake System

There are five major components of ABS: ABS speed sensor, valves, a pump, brake fluid, and a controller.

#1. ABS Speed Sensor.

The ABS sensor normally consists of a toothed ring and a magnet enclosed within a coil. The contact between the ring and the magnet induces an electric field due to which a sign is generated.

This sign is then transformed into a digital signal and sent to the ABS controller. The controller then determines the speed of each wheel individually. ABS sensor is a key component in controlling the drift of the car under any conditions.

#2. Valves.

Valves play a major role in the ABS system it controls the pressure and limits it to a certain amount. When the brake pedal is pushed harder, the valves limit the pressure on the brakes. When a valve is jammed it stops functioning; open, close, or change position.

An inoperable valve will prevent the system from changing or controlling the pressure supplied to the brakes. The valve has three positions open, block, and release.

• In the open position, it allows the pressure to flow through the brake.
• In the block position, it blocks the extra pressure and maintains a limited pressure on the brakes.
• In the release position, it releases the pressure held on the brakes

#3. Pump.

The pump in the ABS is used to restore the pressure to the hydraulic brakes after the valves have released it. The controller will change the pump’s status in order to produce the desired amount of pressure and reduce sliding.

#4. Brake fluid.

In the hydraulic brake fluid system, brake fluid is the main applicator of the brakes. It is used to transfer force from the hydraulic lines to the braking mechanism near the wheels.

As brakes produce a lot of heat, the brake fluid has a high boiling point for effective operations. It also prevents corrosion of the materials in contact.

#5. Controller.

A controller is a unit in the ABS which receives the information from the individual wheel ABS speed sensor. When an individual wheel loses traction, a signal is sent to the controller. The controller will then limit the brake force and activate the ABS modulator.

Types of Anti-Lock Brake Systems

There are three basic types of anti-lock brake systems.

• Four-channel, four-sensor ABS. This system has a separate speed sensor and valve on all four wheels. It’s considered the best system because it monitors individual wheels, ensuring maximum braking force. The ABS will only pulse on the single wheel that’s about to lock up, giving drivers better traction control.
• Three-channel, three-sensor ABS. This setup is found on pickup trucks featuring four-wheel ABS. In this system, both front wheels have individual valves and speed sensors. The rear wheels share a valve and one-speed sensor in the rear axle. Because the rear wheels are monitored together, both wheels must lock up to trigger ABS.
• One channel, one sensor ABS. This system has one valve and one-speed sensor to monitor all four wheels and is located in the rear axle. It’s typically found on pickup trucks that have rear-wheel ABS.

Depending upon the number of speed sensors and valves, the anti-lock braking system is segregated into three types.

Type of ABS	Details
Four channel-four sensor ABS	Each wheel has a separate valve and a sensor
Three channel-four sensor ABS	Separate valves for front wheels. A single valve is for both the rear wheels.
Three channel- three sensor ABS	A valve and a sensor in each front wheel. A valve and a sensor for rear wheels.

How Do I Use Anti-Lock Brakes?

If your car is equipped with an anti-lock braking system, you’ll want to know how to use it correctly. When you’re in a panicked stop or on a slippery road, you may feel or hear the ABS vibrating. Don’t pump the brakes yourself—just continue to apply them firmly and steer your way to safety.

It’s important to know that ABS works with the regular braking system on your vehicle. Even if ABS should fail, you’ll still have the regular braking system at your disposal. If the system does fail, your next best option is to pump your brakes when the vehicle starts to skid.

ABS works best when the tires are properly inflated and in good condition. If ABS is malfunctioning, you may have worn brake linings or air/dirt in the brake fluid. Either way, you’ll need that problem checked and fixed ASAP.

How Effective Are Anti-Lock Brakes?

Drivers are benefitting from the effectiveness of ABS according to an 11-year study in the U.S, conducted by the National Highway Traffic Safety Administration (NHTSA):

• ABS reduces the overall crash-involvement rate by 6% for passenger cars and 8% for LTVs (light trucks, including pickup trucks and SUVs)
• Fatal collisions with pedestrians, bicyclists or animals decrease with ABS: by 13% for cars and 14% for LTVs
• Culpable fatal involvements with other vehicles on wet, snowy or icy roads were reduced by 12% for passenger cars

Additionally, according to the Insurance Institute for Highway Safety (IIHS), the rate of fatal crashes is 31% lower for motorcycles equipped with ABS than for the same models without them.

One thing to note is that while anti-lock braking systems have proven to be very effective on normal road conditions, they can be less effective in certain conditions, such as if there is ice, snow and gravel on the road. These elements can bring additional challenges and make it harder for the vehicle to stop, even with ABS.

When driving during extreme weather, it’s important not to assume ABS will work exactly the way it would in normal conditions. Always exercise caution by driving slowly, allowing more room for the vehicle to stop, and by paying close attention to how your car is reacting to the road.

What is the difference between ABS and conventional automobile brakes?

Conventional brakes allow wheels to be locked by the driver and produce a loss of rolling traction. ABS engages when a wheel speed sensor detects impending wheel lock-up, allowing the vehicle to be steered while helping maintain vehicle stability.

Conventional Brakes

Conventional brakes consist of a basic hydraulic system that sends fluid to each wheel when the brake pedal is applied. This system utilizes a combination of mechanical components to increase the force on the drums or rotors when you press the brake pedal to activate the brakes, bringing the vehicle to a stop. 

In the event of a sudden stop requiring fast, hard, continued pressure on the brake pedal, conventional brakes can allow the wheels to lock up, causing loss of traction and contact with the road.

Related: What is Disc Brake?

Anti-Lock Brake Systems

ABS systems consist of a hydraulic system similar to the conventional system but also have wheel speed sensors, hydraulic actuator, pressure release valves, and the ABS control module or computer.

ABS systems come in three and four-channel systems. Three-channel systems control the braking pressure on both front wheels independently and control the rear wheels together as one.

Four-channel systems are often found on most modern-day vehicles and control all four wheels independently, providing a better level of control.

To take full advantage of ABS’s safety benefits, follow these tips.

Do:

• When you feel or hear the ABS vibrating, press and hold the brake – don’t pump – and steer to safety. Wheel sensors will detect when your car’s tires start to lock, and then repeatedly apply and release the brakes to keep tires from skidding.
• Keep your tires filled at the correct air pressure and in good working condition.
• Check your brake lining and be sure you have clean brake fluid. ABS systems can also fail due to worn brake linings or to air or dirt in brake fluid.
• Give enough distance to stop. Follow at least three seconds behind vehicles when driving in good conditions, and allow more time in hazardous conditions such as wet, icy, or packed snow-covered roads. In ABS-equipped vehicles, stopping distances can increase by as much as 25 percent on loose gravel, sand, or lightly packed snow. No vehicle steers as easily on a slippery road as on dry pavement, but an ABS will still help you steer to safety.

Don’t:

• Pump your brakes or take your foot off the brake pedal, because that will release the anti-lock system. ONLY pump your brake if the ABS fails and your vehicle starts to skid.
• Drive aggressively. Driving around curves faster, changing lanes abruptly, or following too closely isn’t safe with or without an ABS-equipped vehicle.
• Forget to steer. Four-wheeled ABS lets drivers steer in emergency braking situations, but the system itself does not steer. If you need to manually steer while the ABS is working to avoid an obstacle in front of you, avoid sudden or drastic steering changes, and carefully guide your vehicle where it needs to go.
• Be alarmed by mechanical noises or slight pedal pulses while applying the brake in an ABS-equipped vehicle. These conditions are normal and let the driver know ABS is working.

Advantages of ABS Brakes

The primary benefits of anti-lock brakes include:

• Increased Stopping Power, Especially On Ice. ABS technology significantly lowers the risk of your wheels locking up and your vehicle skidding, especially in slippery conditions. It is no exaggeration to say that this can be life-saving, helping drivers to maintain control and to steer out of potentially dangerous scenarios.
• Decreased Insurance Costs. Believe it or not, cars that have ABS technology can keep your auto insurance payments down—precisely because anti-lock brakes have proven, so many times, to lower the risk of accidents.
• Enhanced Resale Value. ABS technology adds to the value of your vehicle. In fact, since it’s so standard-issue on today’s cars and trucks, not having ABS means your vehicle will sell for a lower price.
• Improves Traction Control. Anti-lock braking systems share some of the same basic infrastructures as advanced traction control technology—which makes it easier for manufacturers to install traction control in the factory.

Disadvantages of ABS Brakes

Even though anti-lock brakes are proven to be a safety feature in most situations, and insurers consider them to significantly lower risk for a vehicle, not all drivers are sold on this option for a car or truck. Here are some of the downsides that drivers find in this kind of brake system.

• Inconsistent stop times. Anti-lock brakes are made to provide for surer braking in slippery conditions. However, some drivers report that they find stopping distances for regular conditions are lengthened by their ABS, either because there may be errors in the system, or because the clunking or noise of the ABS may contribute to the driver not braking at the same rate.
• Expense. An ABS can be expensive to maintain. Expensive sensors on each wheel can cost hundreds of dollars to fix if they get out of calibration or develop other problems. For some, this is a big reason to decline an ABS in a vehicle.
• Delicate systems. It’s easy to cause a problem in an ABS by messing around with the brakes. Problems include disorientation of the ABS, where a compensating brake sensor causes the vehicle to shudder, make loud noise or generally brake worse.

FAQs.