What is Antilock Braking System or ABS in cars?

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Antilock Braking System (ABS): Construction And Working

Antilock Braking System (ABS) is a type of active safety system of a vehicle. It is also known as the anti-skid braking system. This system comes into action when the driver suddenly applies the brakes during an emergency. Employing the antilock braking system on cars and bikes is now mandatory in most parts of the world.

The need for Anti-lock Brakes:

Whenever the driver suddenly applies the brakes to a high-speed vehicle, there is always a chance of the 'wheel-lock.' The wheel-lock means that the respective wheel stops suddenly instead of slowly coming to a halt. Due to the wheel-lock, the driver loses control over the vehicle, and the vehicle skids off the road. Thus, a fatal accident takes place. In order to avoid such situations, the manufacturers employ the ABS.


The ABS has the following components:

  1. Wheel speed sensors
  2. ABS control module
  3. Brake control unit
  4. Valves
  5. Pump
components of Antilock Braking System (ABS)
Components of Antilock Braking System (ABS) and its normal operation

Wheel speed sensors continuously monitor the speed of each wheel. As long as all the wheels have comparable speed, the system does not interfere with their operation. However, if the speed sensors find that the speed of any of the wheels is reducing drastically, then it means that the particular wheel is going to lock.

However, the locked wheel hampers vehicle stability. Thus, the vehicle stops responding to the steering input given by the driver. At this moment, the vehicle also starts to skid, thereby causing a fatal accident. To avoid such a mishap, the ABS comes into action.

ABS detects a problem
This is how the ABS detects a problem

How does the ABS work?

After receiving the signal of very low speed from the wheel speed sensor, the ABS module orders the brake control unit to reduce that wheel's braking force. Reducing the braking force means reducing the hydraulic pressure in the brake line acting on that wheel. The Brake Control Unit reduces the line pressure with the help of valves in the system. When the braking force reduces, the wheel starts rotating faster, thereby avoiding the wheel-lock. As the wheel doesn't lock, the steerability of the vehicle remains intact. This means that the vehicle moves according to the driver's input without skidding. Once the normal condition is restored, the Brake Control Unit restores the brake line's hydraulic pressure with the help of a pump.

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