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Anti-Lock Braking System: Technical Details Explained

Anti-lock braking system or ABS is a vital safety feature that has become a common feature in all modern cars. ABS as a feature is often advertised as a system that helps mitigate accidents to a large extent. We explain everything you need to know about ABS, how the system functions, the benefits of the system and the types that you can find in a car you buy today.

What is an Anti-Lock Braking System?

As the name suggests, ABS prevents the wheels from locking when you apply the brakes. Moreover, it also reduces the braking distance and lets you control the vehicle while brakes remain applied. ABS consists of four major components.

Speed sensors: These sensors monitor the speed of the wheels

Valves: Valves in the brake line allow, block and release pressure on the brakes.

Pumps: Pumps are filled with hydraulic fluid that applies pressure to the brake drums or callipers when brakes are applied.

ECU: The electronic control unit (ECU) reacts to the signals from the speed sensors.

How does ABS work?Anti-lock braking system functioning

In standard braking, as you press the brake pedal, the brake pads press against the wheel disc and this stops the rotation of the wheels. With ABS, as you apply the brakes, the speed sensors track the decreasing rotation of the wheels. When the brakes are about to stop rotation, they send a signal to the electric control unit (ECU). The ECU partially releases the brake pads from the wheels through valves and pumps, allowing the wheel to continue rotating. With ABS, the wheels can continue rotating, allowing you to maintain control over the car in a heavy braking situation.

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Without ABS, the wheels would stop or lock up immediately after the brakes are applied and the vehicle would skid due to the translational velocity of the wheels. In this case, due to skidding the vehicle would cover a relatively long distance and you won’t be able to control the vehicle since you can’t steer the locked wheels. Moreover, if the left and right wheels of the vehicle are on different traction surfaces, the application of brakes produces different frictional forces on the wheels. This produces torque and causes the vehicle to spin uncontrollably.

Advantages of Anti-Lock Braking System or ABS

  • An anti-lock braking system reduces the braking distance as the appropriate pressure is applied to stop the car.
  • Since wheels don’t lock up while stopping the vehicle, it avoids uneven tyre wear.
  • ABS helps the traction control system.
  • Reduce wearing of brake pads and brake discs.
  • In case of heavy braking, you can steer the car around obstacles.

Disadvantages of Anti-Lock Braking System or ABS

  • Variable braking distances due to different types of surfaces
  • Increases the overall cost of the vehicle
  • The intricate arrangement of ECU and sensors increases the complexity
  • Expensive to maintain

Classification of Anti-Lock Braking System

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

Type of ABS


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 each rear wheel.


What is the function of EBD with ABS?

In the Anti-Lock Braking system, when the brakes are applied, an electronic control unit doesn’t let the wheels lock and keep them intermittently rotating. During rotation, due to road conditions, different speeds, and loads, all four wheels need a different amount of brakeforce to bring them to rest. The Electronic brakeforce distribution detects the brake force required by each wheel and supplies just as much as needed to keep the vehicle balanced.

What are the mandatory safety features in cars in India?

The mandatory safety features in cars in India are ABS with EBD, rear parking sensors, dual front airbags, rear parking sensors, hill hold control, seatbelt pre-tensioners, and speed sensing door locks.

On what kind of surfaces ABS doesn’t work?

ABS can be ineffective on gravels, icy conditions, or very wet surfaces.

How effective is ABS in preventing accidents?

ABS reduces the overall crash involvement by 6% in passenger cars and 8% in LTVs (light trucks, pick-up trucks, SUVs, and Vans). During braking, ABS prevents the vehicle from skidding which would certainly happen in heavy braking conditions if ABS is not there.

How does ABD help in car racing?

In racing cars, the usage of ABS keeps the tyre wear minimum as drivers frequently apply brakes while taking quick turns.

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