How does the automatic emergency braking system work in cars?

The safest way to drive is to always have your eyes on the road and to drive carefully. However, with technology rapidly opening new doors, there are now driver assistance features in cars that can make your driving safer and take some weight off your shoulders.

These features work on the basis of correcting your slippages. One of the major problems for drivers is not braking when there is an obstacle in your way. This is where Automatic Emergency Braking or AEB comes in.

So what is AEB and how does it work?

What is Automatic Emergency Braking?


Disc brakes on a ferrari.

The AEB or automatic emergency braking system is an active driver assistance and safety function. This feature was first introduced by Volvo in 2008 and is used to prevent accidents and collisions by automatically activating the brakes.

This system constantly receives and monitors information from the environment, such as your distance from other vehicles, their speed and your speed.

If the AEB system detects the sudden stop of a vehicle in front of you or anything that could cause a collision, it will warn you first. If you still refuse to apply the brakes, AEB will intervene and bring the car to a stop to avoid a potential collision or reduce the impact of an unavoidable accident.

How does the automatic emergency braking system work?


Driver inside a car on a road.

Most new cars are already equipped with sensors such as speed cameras. These radars are used in other driving assistance functions such as active cruise control or ACC. AEB can use these radars and other sensors such as lidars and cameras to get a good picture and calculation of the surrounding environment and objects.

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AEB also has access to information about your car via the ECU or electronic control unit. By taking your car’s speed and calculating the distance to an object ahead of you, AEB can calculate and determine if your current speed has the potential to cause a collision.

If AEB detects a potential collision, AEB will check the braking systems. If you have already applied the brakes and are slowing enough to avoid a collision, AEB will not intervene. However, if you did not press the brakes despite the obstacle ahead or if you did not apply enough force to the brakes, the AEB will take over and brake with enough force to avoid the collision.


AEB systems can detect vehicles and large obstacles. However, more advanced models can even detect two-wheeled vehicles and pedestrians.

Some cars take AEB to the next level and come with automatic reverse braking. Reverse Automatic Braking works the same way as AEB, but is designed to prevent low-speed collisions, especially parking collisions where you’re backing into someone else’s car, from happening .

Reverse automatic braking receives information from speed cameras and rear cameras to observe and monitor the rear of the car. If a pedestrian enters while you’re rearing up, or if you get too close to someone else’s car, the reverse automatic braking system will engage and help you avoid a collision.

Related: Standalone vs. Integrated Car Navigation Systems: Which is Better?

Is the automatic emergency braking system reliable?


City traffic as the crow flies.

Institutes like Euro NCAP are constantly pushing for AEB to become a requirement on new cars. This has happened with ABS in the past. Anti-lock braking systems were first introduced as extra equipment on cars, but later became a requirement on every production car.

Despite AEB’s growing reputation, it is important to note that although these systems are tested in environments simulating real-world scenarios and proven to be highly accurate, they are still prone to failure. Sensors such as lidars and cameras lose accuracy in bad weather, and if the car’s AEB system relies on these sensors, it will also fail.

Related: RADAR vs LiDAR: What’s the difference?

This is a contradictory drawback, as automatic emergency brakes would be more useful in bad weather conditions that reduce your view, such as fog and snowstorms. Yet the chances of them failing under these conditions are higher.

Less developed AEB systems also tend to become hyperactive in city traffic. For example, when driving towards a red light where other vehicles have stopped. AEB may see your approach to stationary vehicles as a threat and brake hard.

Reverse automatic braking systems can also become very troublesome if not calibrated correctly. The system can become too sensitive and bring the car to a complete stop even if you have more than enough space to park the car.

Is it worth having a car with automatic emergency brakes?


A wrecked car.

AEB is a valuable and advanced feature to have on your car. AEB requires several parts and sensors to work, but the good thing is that none of these sensors are exclusive to AEB.

A car with AEB is also likely to have active cruise control or even 360 degree cameras. AEB uses the same sensors as these features (radars, lidars, cameras, etc.), so it doesn’t require any parts exclusive to itself.


AEB may seem superfluous and an extra cost, but it is certainly much cheaper than a car accident. According to Euro NCAP research [PDF]AEB can reduce actual rear-end collisions by 31% and save many lives in the years to come.

Related: How does the 360 ​​degree camera work in a car?

Automatic emergency brakes can save lives and money

AEB was once limited to high-end luxury cars, but is now available on many cars as standard. AEB is not perfect. He may sometimes act when not needed or not act when needed. Either way, AEB greatly reduces the risk of an accident or rear-end collision and can save many lives.

Although it remains an optional feature, AEB may become a requirement for new production cars. For example, the Australian government has announced that it will require all new cars to be fitted with AEB from 2023.


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About the Author

Maria D. Ervin