Understanding the working of anti-lock braking system (ABS)

A safety anti-skid braking system known as an anti-lock braking system (ABS) is used on buses, lorries, cars, and motorbikes as well as on airplanes. To retain tractive contact with the road surface and provide the driver with better control over the car, ABS works by preventing the wheels from locking up when braking.

An anti-lock braking system (ABS) plays an important role in an engine braking system. On a slippery road, braking can be very difficult for professional drivers, so it is more for learners. Before this design’s invention, braking was a dramatic event on the road with slippery products.


The existence of ABS has helped to overcome such kinds of events as it prevents the wheels from locking up. It also helps to maintain the grip of the road below. Today we’ll be looking at the definition, functions, applications, components, diagram, types, and working of an anti-lock braking system (ABS). we’ll also enlighten on its advantages and disadvantages, as well as symptoms of bad or failing ABS.


What is an anti-lock braking system?

An anti-lock braking system is a safety device designed for the automotive system to prevent the wheels from locking up under emergency or harsh braking conditions. Almost all modern vehicles including four and two-wheelers now feature the system due to the latest safety regulations.

The ABS comes to the rescue when there is a loss of traction between the tires and the road surface. This causes the tires to skid, resulting in an uncontrollable vehicle. But in situations like this, the vehicle’s wheels continue to be in motion, and the loss of grip may cause the driver or rider to lose control over the steering of the vehicle. This may result in an accident.

Additionally, an anti-lock brake system (ABS) is known to be a safety anti-skid braking system used on aircraft and vehicles such as cars, motorcycles, buses, and trucks. The system allows the driver or rider to have control over the vehicle as the wheels are prevented from locking up during braking. Anti-lock braking also maintains tractive contact with the road surface.

The ABS works with an automated principle of threshold braking and cadence braking. these braking methods were once practiced by skillful drivers before ABS became popular. The ABS works at a much faster rate and is more effective than driver’s control. The system generally improves vehicle control and also decreases stopping distances on dry and slippery surfaces. It also increases braking distance on loose gravel or snow-covered surfaces.

The modern version of the ABS does not only prevent wheel lock under braking but also alters the front-wheel-brake bias. This feature depends on its specific capabilities and implementation, which is known variously as electronic brake force distribution, traction control system, emergency brake assist, or electronic stability control (ESC).

Functions of the anti-lock braking system:

The following are the functions of the anti-lock braking system in automotive engines:

  • The primary purpose of an anti-lock brake system is to have better control of the vehicles, even while driving in obstacles.
  • It features a controller that monitors the speed sensors at all times. It checks for deceleration in the wheel that i out of the ordinary. This occurs right before the wheel locks up, making a rapid deceleration. If the checking never occurs, the wheel stops much quicker than it could.
  • This eliminates the need to manually pump the brakes while driving on a low traction surface or a slippery surface. This allows for efficient steering in most emergency braking conditions.
  • Drivers will experience pulsing in the brake pedal when the system is in operation due to the opening and closing of the valves. The pulsing indicates to the driver that the ABS is working.
  • The ABS controller is a program to know the rapid deceleration of a car is impossible. This means when a rapid deceleration happens the wheel is about to slip, so it reduces the pressure to take that brake until it experiences an acceleration. This is when it increases the pressure until its deceleration occurs.

Read: Understanding automotive braking system


Components of anti-lock braking system

Below are the components of an anti-lock braking system and their functions:

Speed sensors:

A speed sensor is also known as an encoder as it helps to determine the acceleration or deceleration of the wheel. The component works with a magnet and a hall effect sensor, or a toothed wheel and an electromagnetic coil to produce a signal.

As the wheel rotates, it induces a magnetic field around the sensor, which generates a voltage in the sensor as the magnetic field fluctuates around it. The sensor becomes inaccurate at slow speeds because the slower rotation of the wheel can cause incorrect fluctuations in the magnetic field. This cause in causes inaccurate readings to the controller.


The anti-lock brake system contains a valve as its component. It’s controlled by ABS itself and usually has three positions on some systems. in position one, the valve opens allowing pressure from the master cylinder to pass right through to the brake. In position two, the valve blocks the line, separating the brake from the master cylinder. If this happens, the pressure is prevented from rising further. In the third position, the valve releases some pressure from the brake. A clogged valve is a common problem that occurs in the anti-lock braking system.


The controller serves as an ECU device as it receives information from each wheel speed sensor. A signal is sent to the controller if the wheel loses traction. The controller will limit the brake force (EBD) and then activate the ABS modulator which actuates the braking valves on and off.


The function pump is to restore the pressure to the hydraulic brakes after the valves release it. a controller shows a signal that releases the valve when a slip is detected in the wheel. The pump restores a desired amount of pressure to the braking system as soon as a valve releases the pressure applied by the driver. The controller will then modulate the pump’s condition to provide the desired amount of pressure and reduce slipping.

Anti-lock braking system diagram:

components of antilock braking system

Types of anti-lock braking system

Anti-lock braking systems work with various schemes depending on the types of brake employed. Below are the types of anti-lock braking systems in automotive vehicles:

Four-channel, four-sensor ABS

These types of ABS contain a speed sensor on the four wheels and a separate valve for all four wheels. This setup allows the controller to monitor each wheel individually, ensuring the maximum braking force is achieved.

Three-channel, four-sensor ABS

This anti-lock braking system setup contains a speed sensor on all four wheels and a separate valve for each of the front wheels. One valve is employed for both wheels at the rear. These types of ABS are used on older vehicles with four wheels.

Three-channel, three-sensor ABS

This system carries a speed sensor and a valve for each of the front wheels. The rear wheels feature one valve and one sensor for both wheels. This scheme is commonly found on pickup trucks with four-wheel ABS. In this system, individual control is provided in the front wheels, so that maximum braking force can be obtained. The rear wheels have to start to lock up before the ABS will activate on the rear. However, the wheels are monitored together.

In these types of anti-lock brake systems, there is a possibility that one of the rear wheels will lock during a stop. This will reduce brake effectiveness. Well, the system is easy to identify since there are no individual speed sensors for the rear wheels.

Two-channel, four-sensor ABS

This system is commonly found in passenger cars that exist from the late ’80s through the mid-90s. It works with a speed sensor at each wheel and one control valve for each of the front and rear wheels as a pair. If any lock-up is detected by the speed sensor in any individual wheel, the control module pulses the valve for both wheels on that end of the car.

One-channel, one-sensor ABS

This system is commonly used on pickup trucks, vans, and SUVs as it contains one valve that controls both rear wheels. It also has a one-speed sensor, located in the rear axle. Its working is just like the rear end of a three-channel system. The rear wheels are monitored together and they have to lock up before the ABS actuates. In this system, there is also a possibility that one of the rear wheels will lock, which reduces brake effectiveness. and the system is easy to identify, as there are no individual speed sensors for any of the wheels.

Working principle

The working of an anti-lock braking system is less complex and can be easily understood. Though a lot has been mentioned while explaining the various types and components of the system. but stay focused as I enlighten more on how it works.

An anti-lock braking system works with the regular braking system as it automatically pumps them. It’s done manually by drivers in vehicles that are not equipped with the system, which prevents wheel lockup. In vehicles equipped with ABS, the driver’s foot should be firmly placed on the brake pedal, while ABS pumps the brake automatically. This allows the driver to concentrate on steering safely.

The actuation of the ABS causes the brake pedal to pulse noticeably as some inexperienced drivers think that’s brake failure. Some system is additionally designed to monitor the rate of acceleration released or the time between accelerator release and brake application. The system will then automatically increase the braking force where enough pressure is required.

Just as earlier mentioned, the anti-force braking system monitors the wheels under heavy braking. it’s commonly known as electronic stability control, which helps to achieve the monitoring. Depending on the type, each wheel has a sensor, which detects when a wheel is about to lock up and stop moving. The system will then release the brake, enabling it to move. The ABS continuously applies optimum braking pressure to each wheel, allowing a level of braking to occur and not completely locking the wheels.

With this effect, the risk of skidding is reduced even when excessive evasive maneuvers happen. This is why the driver should know the braking distance may increase. This means the car might not stop immediately while driving on an obstructed road.

Watch the video to understand more about how ABS works:

Advantages and disadvantages of anti-lock braking system


Below are the benefits of an anti-lock braking system:

  • ABS prevent lockups and skidding, even in slippery conditions like stopping on ice, oily, or wet road. The system is assured to save a life in such a condition, giving the driver perfect control of the vehicle.
  • Due to the effectiveness of the device, it’s now mandatory by law for all vehicles to feature them. This makes it easy for drivers to purchase devices that carry the system at low insurance costs.
  • Modern ABS is designed to have a traction control system, which allows all-wheel traction on the road. This makes it easy for manufacturers to do both features in the factory.
  • Cars or trucks feature anti-lock brake systems and have higher resale value as the system continues to rise.

Read: How much brake fluid do I need? (What you need to know)

Disadvantages of anti-lock braking system

Despite the advantages of ABS, some limitations still occur. Below are the disadvantages of an anti-lock braking system:

  • The system is delicate. it’s easy for the system to cause problems to the brakes such as disorientation of the ABS, where the vehicle is caused to shudder because of the brake sensors.
  • An anti-lock brake can be expensive to maintain depending on the car model. Sensors on each wheel can cost much to fix when they develop a fault. This is the reason why most people don’t have ABS on their vehicles.
  • ABS ensures ideal braking in slippery conditions, but some users complain of inconsistent stop time. That is, the stopping distances for regular conditions are lengthened by their ABS. This is caused by an error in the system.

Read: What does the brake system warning light mean? How to fix

Related Article:

In conclusion, an anti-lock brake system is found important in all kinds of automobiles as drivers tend to have control while driving on a bad road. We’ve examined a lot about that in this article. I hope you found the article helpful, if so, you can tell us your favorite aspect of the system in our comment box. And don’t forget to share this article with other technical students. Thanks!


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