You were driving on an expressway when something came in your way out of nowhere, you hit the brakes instantaneously, and in a matter of seconds, your vehicle stopped.

Although your reflexes were hard at work in this situation, you should know that without an Antilock Braking System (ABS), you would have lost control of your car.

So, what is ABS, and how does it enable drivers to control their vehicles in situations of emergency? Let's talk about ABS and how it works.

What Is ABS, and Why Is It Needed?

Short for Antilock Braking System, ABS is a braking technology that prevents your tires from locking during emergency braking.

Invented by Mario Palazzetti in 1971, the Antilock Braking System is an old safety standard when compared to newer automated vehicle safety technologies, but according to a US Department of Transportation study of accidents between 1995 and 2007, ABS was estimated to have reduced non-fatal accidents by six percent in cars.

This raises questions: why do tires lock during braking, and why is this phenomenon so dangerous?

Well, when your car is moving at a high velocity, it has a lot of kinetic energy, and the same needs to be converted into another form of energy to stop the vehicle.

When you apply the brakes on your vehicle, this kinetic energy converts into heat, and once all the kinetic energy is consumed, the car comes to a stop. In normal braking conditions, this process happens over a prolonged time frame, and the wheels don't lock as the brakes are applied gradually.

A car drifting on a track

In the case of emergency braking, a lot of pressure is applied to the moving tires in a very small duration. Due to this, a high stopping force is applied to the tires causing them to lock. This locking prevents the loss of energy through the brakes.

Therefore, to lose the kinetic energy, the vehicle starts to slip. This slipping phenomenon prevents the driver from maneuvering the car, making tire locking extremely dangerous.

To solve this problem, cars are equipped with the Antilock Braking System. The main job of this system is to get the wheels into motion in emergencies helping the driver regain control of the car.

Understanding the Moving Parts of an Antilock Braking System

Now that we understand why we need ABS, we can look at the various systems which come together to make vehicle braking safer. Although ABS is not as advanced as Automatic Emergency Braking System technology it has several moving parts and a brief overview about the same is given below

  • Wheel speed sensors: Every wheel on your car comes with a wheel speed sensor. This sensor consists of a perforated magnetic ring and a Hall effect sensor. As the wheel rotates, the magnetic field created by the ring changes periodically. The Hall effect sensor collects this data enabling the sensor to calculate the speed of the wheels.
    A microcontroller on a table
  • Electronics Control Unit (ECU): Just like a CPU is the brains of a personal computer, an ECU is a computer that monitors the critical operations of your car. This includes tasks like monitoring the amount of fuel and air entering your engine, but unlike personal computers, a car has several ECUs. This is because an ECU performs a set of tasks with high accuracy rather than performing several tasks. Therefore, in a vehicle, different ECUs communicate with one another and ensure that critical functions like ABS perform in an optimized manner.
  • Hydraulic systems: When you press the brakes in your car, it activates the hydraulic system, responsible for transmitting brake fluid to the brake pads. This fluid applies pressure to the wheels, and the same is directly related to the force you apply to the brakes. So if you hit the brakes hard, the hydraulic system squeezes the brake pads against the wheels with the necessary pressure.

The wheel speed sensor along with the ECU and the hydraulic system work together to prevent tire locking during emergency situations.

How Does ABS Work?

Now that we understand the various moving parts of an Antilock Braking System, we can look at how the system works.

It all starts with the wheel speed sensor. This sensor continuously monitors the tires' speed and sends this data to the ECU.

A graphic describing how ABS works

The ECU analyzes this data and tries to understand if the car's wheels have locked. If the tires have locked, the Antilock Braking System comes into the picture and tries to get the wheels spinning again. To do this, the ECU starts controlling the hydraulic system and varies the pressure applied on the tires to ensure that they don't lock.

This variation in pressure is based on the speed of the tires. So if the tires are locked, the ECU reduces the pressure on the wheels, and if the wheels are spinning at a high velocity, the ECU increases the pressure applied to the tires.

The above-mentioned procedure of varying the pressure is performed several times in a second, ensuring that the vehicle stops in a controlled manner.

Does ABS Reduce Stopping Distance?

Most people are under the impression that ABS makes their cars stop in a shorter duration of time, but it's not always true. As ABS applies breaks repeatedly to prevent the tires from locking, it can increase the braking distance. The critical thing to understand here is that an Antilock Braking System provides control to a driver rather than stopping the vehicle faster.

Does Pumping Brakes Make ABS Better?

Also known as cadence braking, brake pumping is a process of applying brakes repeatedly to regain control of a skidding vehicle that does not have ABS.

If a vehicle has ABS, then cadence braking can be counterintuitive as it changes the pressure in the hydraulic system, and the same can cause the ABS to malfunction.

Is ABS Making the World a Safer Place?

Antilock Braking Systems combine state-of-the-art sensor technologies with algorithms working on ECUs. These technologies help drivers in regaining control of their vehicles in dire situations.

Therefore, the next time you hit the brakes hard, remember that the brains of the car and your reflexes worked together to save your life.