Autonomous Emergency Braking (AEB) in cars and how it works

Team Ackodrive6, Jun, 2022

With the emergence of several new active and passive safety features, cars have become a lot safer in the past decade. You can drive your car worry-free, knowing that the safety features will do their job efficiently. In recent years, driver assistance safety features have become common in cars, and one such feature is the Autonomous Emergency Braking (AEB). The name itself may give you an idea about what exactly AEB does. In this article, we discuss AEB in cars and its working mechanism.

Autonomous Emergency Braking in Cars

What is Autonomous Emergency Braking (AEB) in cars?

Autonomous Emergency Braking or AEB is an active safety feature in cars that automatically applies the brakes in emergencies. Car manufacturers use different brand terms for AEB, such as automatic emergency braking, brake assist, brake support, etc. Whatever the name is, the system's primary function — which we are going to explain in a while — remains the same.

AEB, as the name suggests, is an automatic braking system. The system detects obstacles (pedestrians, vehicles, etc.) and automatically applies the brakes or increases the braking force if the driver is applying the brakes insufficiently. AEB can slow down the car and stop the vehicle, depending on the speed, to avoid a potential collision. It's a highly efficient safety feature as it assists the driver or automatically applies the brakes if the driver fails to do so.

Autonomous braking systems can be of different types depending on the make and model. Below are different kinds of AEB in cars.

1. Forward automatic emergency braking

In this type of system, AEB works in conjunction with the Forward Collision Warning (FCW) system. FCW alerts the driver by sound or a visible sign on the dashboard. Generally, FCW activates before AEB kicks in. First, the FCW warns the driver about the obstacle ahead, and if the driver fails to take appropriate action, the automatic braking system intervenes.

2. Rear automatic emergency braking

It is a system where AEB comes into action if it detects any obstacles while reversing the car. It can be more of a convenience feature than a safety feature. In some vehicles, the rear AEB works with the rear cross-traffic alert, which detects the movement of vehicles behind your car when you are reversing. Reverse automatic braking can be helpful when reversing from a very tight parking spot.

3. AEB with pedestrian detection

This system is similar to forward AEB, where the autonomous braking system pairs with the forward-collision warning system capable of detecting pedestrians, cyclists and even large animals. If the FCW detects any pedestrians in front of the vehicle, the AEB applies the brakes to slow down or stop the car, provided the driver does not engage the brakes.

4. City speed AEB

As the name suggests, the system prevents collisions in cities, heavy traffic or parking lots. In other words, the city speed AEB works only at lower speeds. For instance, if you are driving on the road with bumper-to-bumper traffic, the AEB-city can avoid rear-ending a vehicle if you fail to apply the brakes in time. It’s a handy safety feature as it can prevent slow-speed collisions in cities.

5. Highway speed AEB

The name of the system is self-explanatory. In this system, the AEB works at high speeds, especially when driving on a highway. The AEB-highway system uses more advanced sensors to detect far-away obstacles. However, this type of automatic braking system can only slow down the car as much as possible before the collision, and it cannot bring the vehicle to a stop. So, the driver’s attention is required to avoid the collision, even with the AEB intervention.

How does the AEB system work?

AEB driver assistance system works with the help of a network of radar sensors mounted on the front grille, bumpers or windshield. Some systems also rely on cameras, and some advanced systems use both radar sensors and cameras. Initially, the use of radar sensors and cameras came into effect to enable the Adaptive Cruise Control feature, and AEB also relies on the same set of equipment.

Glance through the points below to understand the automatic emergency braking system working mechanism.

  • The sensors and/or cameras constantly monitor the distance between your car and the obstacle (moving car, pedestrian, etc.) ahead. 

  • If the distance reduces rapidly, for instance, if the vehicle in front brakes suddenly, the system immediately triggers a warning. 

  • The driver receives an alert message via an audio or visual medium.

  • If you are too late to react, the AEB comes into action and automatically applies the brakes.

  • The ECU (Electronic Control Unit) monitors your input and can detect when you are off the throttle and applies the brakes manually. So, AEB will not kick in unnecessarily.

  • The Anti-Lock Braking System (ABS) helps AEB stop/slow down the vehicle efficiently.

  • The entry-level AEB systems work only at slow speeds. They can be helpful when you drive in the city.

  • The more sophisticated automatic braking systems work across a wider speed range. Hence, they may avoid or mitigate the intensity of a high-speed collision.

  • The most advanced AEB systems can also detect stationary objects, moving pedestrians, cyclists and cars.

Top AEB cars in India

Safety has been one of the talking points of the Indian automobile industry in the past few years. With essential safety features such as dual front airbags, ABS and rear parking sensors mandatory in India, the cars are much safer. However, AEB is not compulsory in India. But the government is mulling making active safety features mandatory in the coming years.

As of March 2022, only a few luxury and premium car brands offer automatic emergency braking. Below are the cars with autonomous emergency braking in India.

SUVs (Sport Utility Vehicle) with AEB

  • MG Astor

  • MG Gloster

  • Mahindra XUV700

  • Volvo XC40

  • Volvo XC60

  • Volvo XC90

  • Mercedes-Benz GLS

  • Mercedes-Benz G-Class

  • Mercedes-Benz GLE Coupe

  • Mercedes-Benz GLE

  • Mercedes-Benz GLA

  • BMW X7

  • Audi Q8

Cheapest cars with AEB

Below are some of the most affordable cars with AEB.

Model Price (Ex-showroom Delhi)
MG Astor Rs. 9.98 lakhs to Rs. 17.72 lakhs
Mahindra XUV700 Rs. 12.95 lakhs to Rs. 23.79 lakhs
MG Gloster Rs. 30.99 lakhs to Rs. 38.99 lakhs
Volvo XC40 Rs. 43.25 lakhs
Mercedes-Benz GLA Rs. 44 lakhs to Rs. 48.10 lakhs
Volvo XC60 Rs. 63.50 lakhs

Note: AEB is available in select variants of some models.

Why is AEB so important?

AEB is an efficient active safety feature in cars. The points below explain the importance of the automatic braking system in cars.

  • AEB can avoid a potential collision or reduce the magnitude of impact in case of a high-speed collision.

  • Since AEB is an automated system, the reaction time is way quicker than human reaction time. The quick reaction time during braking can save your and other motorists' lives.

  • An autonomous emergency braking system comes in handy if the visibility is too low. The system can detect obstacles and brake automatically, even if the visibility is low.

  • AEB is an important safety feature, especially during night drives. If you fail to notice any obstacles or your reaction time is too slow, it will come to your rescue.

Autonomous braking vs anti-lock brakes

Autonomous braking is an automated system, whereas Anti-lock Braking System (ABS) activates if you manually apply the brakes. However, both the systems fall under the active safety features category, but their function and purpose are different. Refer to the table below for more details on AEB vs ABS.

Parameters Autonomous Emergency Braking (AEB) Anti-lock Braking System (ABS)
Purpose To avoid collision with an obstacle (vehicle, pedestrian, etc.) or mitigate the magnitude of impact due to collision. To avoid lock-up of wheels under panic/emergency braking.
Working mechanism The AEB system monitors the vehicle’s surroundings via sensors/cameras and detects the obstacles. The system triggers a warning to the driver about a potential collision, and if the driver is late to respond, it automatically applies the brakes. ABS detects the wheel lock-up via speed sensors on the wheels. Next, the system releases the brakes to prevent lockup and applies the brakes again to slow down/stop the vehicle. The cycle repeats until the car stops safely.
Category Active safety feature Active safety feature
Driver input No driver input is required as it automatically applies the brakes. The system activates only if the driver applies the brakes.
Application AEB is not mandatory in India and can be found in a few luxury and premium cars. ABS is mandatory for all cars in India.
Cost Expensive Affordable

Automatic emergency braking: pros and cons

Below are some of the advantages and disadvantages of the automatic emergency braking system.

Pros of autonomous emergency braking system

Here are the pros of AEB in cars.

  • One of the most significant advantages of AEB is that it can avoid a potential collision.

  • If you are driving on a highway, the system can drastically reduce the vehicle speed before colliding with an obstacle. It reduces the intensity of the impact, and it can save your life.

  • It’s an efficient safety feature since it does not require human input.

  • The fast reaction time of AEB can save you from tricky situations.

  • Advanced AEB systems can work at slow and high speeds. Hence, it is useful both in cities and highways.

  • AEB can enhance the braking force if you are not applying the brakes with enough force.

Cons of autonomous emergency braking system

Below are some of the disadvantages of the automatic emergency braking system.

  • AEB is an expensive system. Hence, cars with automatic braking systems are expensive.

  • Automatic braking can kick in falsely and jam the brakes. For example, if you are parking the car in a very tight spot, AEB can trigger the brakes, which can be a shocking manoeuvre to the driver.

  • Some drivers can be over-reliant on AEB and may not pay attention to the road ahead.

AEB systems by car manufacturers

As mentioned earlier, different car manufacturers have different names for the autonomous emergency braking system. Refer to the table below to know the terms of AEB systems by different car manufacturers.

Brand AEB system name
MG Motor Autonomous Emergency Braking (AEB)
Mahindra & Mahindra Automatic emergency braking
Volvo Auto brake
Mercedes-Benz Active braking assist
BMW Light city braking function
Audi Audi pre-sense basic

Will AEB be fitted as standard in the future?

Currently, only a handful of cars come with automatic emergency braking systems. And most of the vehicles belong to the luxury or premium segment. Also, the safety feature is not available as standard on all variants of some of the models. Since AEB is not mandatory in India, it is not available with all cars.

However, it may all change in future as the government is mulling over making autonomous emergency braking systems mandatory in India by 2022-23. Once it is compulsory, all cars will be fitted with AEB as standard safety equipment. It will make the cars and the Indian roads a lot safer, especially for pedestrians and cyclists.

How effective is automatic emergency braking?

As you already know, AEB is an automatic braking system that does not require any human intervention or requires very little driver input.. Hence, it is highly efficient and effective in emergencies. Since the system is electronically controlled, the reaction time is super quick, and it can effectively avoid collisions by automatically applying brakes.

Frequently Asked Questions (FAQs)

Let's look at some of the frequently asked questions and their answers related to vehicles with autonomous emergency braking.

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Can I turn off the automatic emergency braking system in my car?

Yes, you can switch off the AEB function, provided your car has an option to do it. The process of turning off automatic braking can vary depending on the car and the braking system. But most cars do come with an option to disable autonomous emergency braking.

Why don't all cars in India have an AEB system?

Automatic emergency braking is an advanced safety feature. Incorporating such a feature is an expensive affair for car manufacturers. That's the reason why car manufacturers do not provide AEB in mass-market cars. Including such a feature would increase the vehicle's cost, and that's not a good thing in a price-sensitive Indian market. Another reason for not including AEB in all cars is that it is not a mandatory safety feature in the country.

Where is the AEB sensor located in my car?

Generally, autonomous braking system sensors are located on the front of the vehicle on the grille, windshield or bumper. 

Are there any affordable small cars with AEB as standard?

Unfortunately, there are no affordable small cars with AEB, even as an option. Since automatic emergency braking is an expensive technology, it is available only on the premium and luxury cars.

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