What is autonomous emergency braking (AEB)?

  • How does AEB work?
  • Do you need it?
  • Parkers explains the tech

Autonomous emergency braking (AEB) is a safety system that detects a potential crash ahead and prepares the car by either audibly warning the driver or taking evasive action itself by applying the brakes.

How does autonomous emergency braking work?

Using a combination of radar sensors and/or cameras, AEB constantly scans the road ahead for any potential hazards – mostly around town below 25mph where the majority of incidents occur.

If the car senses a crash is about to happen, an audible warning is given to the driver along with visual warnings either on the dashboard or head-up display. If this is ignored and no action is taken, the car will brake automatically to reduce the impact severity or the collision altogether.

If the car is going too fast, the brakes are applied to reduce the impact, while many city-focused systems are capable of bringing the car to a complete stop altogether.

In some cases, the AEB system works in cooperation with a car’s other safety systems (where fitted) to protect the occupants further. For example, tensioning the seatbelts and putting on the hazard warning lights for cars behind, while more advanced systems can detect pedestrians, animals and cyclists, not just vehicles.

Different systems also work at different speeds; some are just at city speeds while others work in motorway conditions, too.

Do I need it?

Yes – at least if you want your new car to have a five-star Euro NCAP safety rating. A full five-star rating will only be given to cars fitted with AEB.

It’s a valuable piece of safety equipment that’s becoming standard-fit on more and more models, so it’s likely your next car will come with it anyway. Still, it could prove life-saving in split-second situations where the car is able to react quicker than the driver.

In some cases, cars fitted with AEB fall into slightly lower insurance groups than those without it fitted, too.

Found on

Volvo debuted the technology back in 2010, but now you can get it on anything from the Volkswagen Up through to the BMW 7 Series.

Also known as

Manufacturers have their own names for automatic emergency braking, for example City Braking (Volvo), Front Assist or City Emergency Braking (Volkswagen), Pre Sense Front (Audi), Collision Mitigation (Honda) and Pre-Safe (Mercedes) to name just a few.

This is similar to forward collision warning, which detects the same potential impacts and warns the driver to take action, but won’t automatically brake the car. 

Looking for more jargon-busting motoring meanings? Head over to our Parkers Car Glossary page and take a look at our other definitions.