Guide to Automatic Emergency Braking

How AEB can put the brakes on car collisions

By Keith Barry

Automatic emergency braking (AEB) is a popular technology among Consumer Reports members, and it’s easy to see why: the saving of bacon.

“I try to not follow the next car closely. But [AEB] has saved my bacon on the freeway and around the town a few times,” the owner of a 2018 Toyota Camry Hybrid told CR in response to a recent car-safety survey.

“Within [the] first week of ownership, [I] had an incident where the braking system brought me to a full stop prior to [a] collision. In heavy traffic, another car crossed three lanes and came to a stop in front of me,” wrote the owner of a 2019 Subaru Outback. “The system took over and brought the car to a screeching halt. Saved our bacon.”

If a car equipped with AEB senses an imminent collision and the driver doesn’t react in time, the car starts braking on its own. Some systems apply only a portion of the braking power, so drivers will want to apply the full brakes as well. Data from the Insurance Institute for Highway Safety (IIHS) shows that rear-end collisions are cut by 50 percent for vehicles equipped with AEB and forward collision warning (FCW). Due to a voluntary commitment in which automakers have agreed to equip FCW and AEB as standard equipment on nearly all new passenger vehicles by Sept. 1, 2022, a vast majority of new cars on sale today have AEB as standard equipment.

Common variations:

Automatic Emergency Braking (AEB): Detects potential collisions with a vehicle ahead, provides forward collision warning, and automatically brakes to avoid the collision or lessen the severity of impact.

Automatic Emergency Braking With Pedestrian Detection (AEB-ped): Detects potential collisions with pedestrians or bicyclists while the car is traveling forward and automatically brakes to avoid the collision or lessen the severity of impact.

Some AEB systems operate only at city speeds, which are typically at 55 mph and below. Other AEB systems can work at highway speeds, which are typically above 55 mph.

Rear Automatic Emergency Braking (AEB-rear): Brakes are automatically applied to prevent a collision or reduce impact force while the car is traveling in Reverse.

In our most recent survey, we asked CR members to rate their experiences with the advanced safety and driver-assistance systems on their 2017-2022 cars. Respondents answered questions about their satisfaction with the systems. The survey covered about 47,000 vehicles.

What Makes a Good Automatic Emergency Braking System?

“The best AEB systems are the ones you never notice until you need them most,” says Kelly Funkhouser, manager for vehicle technology at CR. “They are designed to only activate at the last possible second, so it’s common to have never experienced an AEB event." Our survey respondents tended to agree, with a majority of owners telling us they were “very satisfied” with their AEB systems.

But it’s important to remember that AEB isn’t foolproof and that today’s AEB systems can’t prevent all collisions. Even high-speed AEB systems can only slow a car down in some cases, mitigating a crash rather than preventing it. And studies show that AEB with pedestrian detection can’t always see pedestrians and cyclists at night or in turns. “It’s important to remember these systems are using cameras and sensors that can get dirty, blinded by sunlight, or obscured in the rain,” Funkhouser says. “Never rely on these systems to work perfectly, and always stay vigilant.”

Some systems have been a little overzealous in deciding when to hit the brakes. The National Highway Traffic Safety Administration (NHTSA) is investigating complaints of unexpected braking in some 2017-2019 Honda vehicles. Nissan updated the software in some of its 2017-2018 Rogue SUVs to address false braking, And both Tesla and Mazda have recalled cars to fix unexpected AEB application.

CR’s take: FCW and AEB are available in most new cars, but the two safety features are still not yet standard equipment across the industry. CR believes these systems should come with all trim levels, given their ability to save lives. Extra credit is awarded in our Overall Score for models that have systems that can operate at highway speeds and detect pedestrians as standard equipment. Drivers should be aware that AEB is a last resort—not a system that they should rely on.

Brand Names for AEB

CR, AAA, J.D. Power, and the National Safety Council have agreed on specific standardized names for individual safety systems in order to reduce confusion and improve consumer understanding of what they do. Still, manufacturers often use their own names. These are some that automakers use or have used for AEB and packages that have AEB:

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