Anti-Lock Braking System (ABS) Functionality

When the wheels of a vehicle lock up on a slippery or wet road, skidding is often the result. Anti-lock braking systems (ABS) keep your wheels in constant tractive contact with the road which prevents skidding. ABS works on the principles of the cadence and threshold braking systems. However, it does the job with more control and at much faster rate.

Components of Anti-Lock Braking Systems (ABS)

Anti-lock braking systems (ABS) feature four main components:

  • Controller
  • Pump
  • Valves
  • Wheel Speed Sensors

Each of these components works together to keep your car from going into a skid.


The controller works as an ECU unit in the vehicle. It receives information from the wheel speed sensors which send a signal to the controller if a wheel loses traction. The controller then limits the braking force as well as activates the ABS modulator which further activates the braking valves.


The pump in the anti-lock braking system restores the pressure released by the valves to the hydraulic brakes. At the first detection of wheel slip, the valve releases when the controller sends the signal. The pump restores the desired amount of pressure released by the valve to the braking system. The controller modulates the status of the pumps to provide the amount of pressure desired to reduce slipping.


Each brake controlled by the ABS includes a valve in its brake line. The valve in some systems has three positions. In the first position, the valve is open. The pressure is passed right from the master cylinder to the brake. In the second position, the valve blocks the brake line which isolates it from the master cylinder. This valve position doesn’t allow the pressure to increase. In the third position, the valve releases pressure from the brakes.

Wheel Speed Sensors

Wheel Speed Sensors determine the acceleration and deceleration of a wheel. The speed sensors use a Hall Effect sensor and a magnet, or an electromagnetic coil and a toothed wheel for generating a signal. The differential or rotation of the wheel creates a magnetic field around the speed sensor. The magnetic field fluctuation generates a voltage in the speed sensor.

The Working of the Anti-Lock Braking System

The anti-lock braking system works with the regular braking system by pumping them automatically. The controller of the Anti-Lock Braking system monitors the sensors at all times. It looks out for any unexpected decelerations in the wheels. If a deceleration is sensed, the ABS system works to stop the vehicle evenly and quickly.

Such a rapid deceleration isn’t possible without reducing the amount of pressure to that brake until the brake reaches the point of acceleration. The controller then increases the pressure until the vehicle decelerates again. ABS handle this before the wheel can change the speed. As a result, the speed of the wheel slows down. At this point, the brakes keep the wheels close to the lock up threshold. This provides maximum braking power to the system.

Does the Anti-Lock Braking System work?

Yes, the anti-lock braking system helps stop a vehicle safely. The system prevents the wheels of the vehicle from locking up and stops the vehicle in the shortest distance possible, even on the slippery surfaces.

According to a study conducted in 1996 by the Insurance Institute, cars equipped with ABS were involved in fewer fatal accidents than the cars that didn’t feature this system. The study stated that although vehicles equipped with ABS were less likely to encounter fatal accidents involving other cars, they were more likely to meet fatal accidents than others. There are a number of speculations for this.

According to some, the drivers operating the cars equipped with ABS used the system incorrectly, either by releasing the brakes or pumping the brakes.

Nevertheless, the recent reports state that the accident rate for cars fitted with an ABS is improving. Regardless, the effectiveness of this system cannot be disregarded. It does work as intended when driver error does not come into play.

When used correctly, a vehicle with ABS slows down more quickly than a vehicle equipped with simply a threshold braking system. It is wise to know how to apply the ABS and how to drive in inclement conditions to maximize safety.


The Dos and Do Nots of Using ABS

  • Do apply the brakes as hard as possible and hold until the ABS completes its job to stop the vehicle.
  • You should have your ABS system inspected on a regular basis to ensure maximum safety.
  • Do steer and brake at the same time as ABS allows for this functionality, unlike threshold brakes, increasing the chance to avoid an accident.
  • Don’t ever pump the brake pedal in a vehicle fitted with ABS as this isn’t required.
  • Don’t ever take your foot off of the brake pedal if you need to quickly stop as this will increase the likelihood of an accident occurring.



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