Guide to Automatic Emergency Braking
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Automatic emergency braking (AEB) is an advanced safety feature that automatically applies a car’s brakes when it detects a potential collision with an object in its path.
Research from the Insurance Institute for Highway Safety (IIHS) suggests that automatic emergency braking, in conjunction with other advanced safety features like forward collision warning, can reduce the risk of rear-end crash injuries by half.
Automatic emergency braking is available in most new cars, however, it isn’t federally mandated yet. The U.S. Department of Transportation proposed a rule in 2023 that would require all passenger cars and some trucks to have AEB systems.
How does automatic emergency braking work?
When AEB detects a potential collision with an object ahead and a driver doesn't react in time, it autonomously applies the brakes to slow the car down or bring it to a complete stop. The system does this by using cameras, radars and sensors located in or on the front of the car to detect how close a driver is to the object in front of them.
In most new cars, AEB is often paired with forward-collision warning (FCW) technology, which alerts drivers with an audible, visual and/or tactile warning when it detects an object in a vehicle’s path. This means that when equipped with FCW and AEB technology, a car will issue a warning before a potential frontal collision as well as autonomously press the brakes, if the driver doesn’t react in time.
Some vehicles also come with rear automatic emergency braking, which automatically applies the brakes while a car is in reverse, to prevent a potential collision with an object behind it. Rear AEB is typically paired with a warning system as well.
What to know about automatic emergency braking
The specifics of how automatic emergency braking functions vary between vehicle makes and models. There are some systems, for instance, that have pedestrian detection which means they can detect people, large animals and bicycles in addition to cars. This is not the case for all AEB systems, however — many can only detect other vehicles.
Moreover, some car models have low-speed emergency braking systems. This means that they only function at city speeds, typically 55 mph or below. Alternatively, high-speed emergency braking systems primarily work at highway speeds, and will brake to slow the car down as much as possible when it's traveling 55 mph or above. Most newer car models have AEB systems that function both at low and high speeds.
While AEB systems can reduce crash rates and lessen the severity of a collision, they are not infallible systems. For example, the feature often relies on sensors and cameras which can often be covered by dirt, snow or other buildup and which can prevent it from working properly. Similarly, glares from the sun can block sensors and hinder automatic emergency braking systems from functioning optimally. This is why it's important to maintain a safe distance from vehicles ahead while driving, and not to rely solely on automatic emergency braking to prevent potential collisions.
