Automatic Emergency Braking: How It Works

Car Owl

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Summary

• AEB can prevent crashes: The system brakes automatically when it detects an obstacle.
• Standard on most new cars: Required on all new EU cars since 2024.
• Works best at low speeds: Most effective in city driving and traffic.

Automatic Emergency Braking (AEB) is one of the most important safety features on modern cars. It can apply the brakes before you even realise there's danger. Here's how it works.

What Is Automatic Emergency Braking?

AEB is a safety system that automatically applies the brakes when it detects an imminent collision. It works without any input from the driver.

The system uses sensors to constantly monitor the road ahead. If it detects a vehicle, pedestrian, or obstacle and calculates a crash is likely, it takes action.

How AEB Works

Detection

AEB systems use various sensors to detect obstacles:

• Radar: Measures distance and speed of objects ahead
• Cameras: Identify vehicles, pedestrians, and cyclists
• Lidar: Uses laser light for precise distance measurement
• Ultrasonic sensors: For close-range detection at low speeds

Most systems combine multiple sensor types for better accuracy.

Warning

When the system detects potential danger, it typically warns you first:

• Visual warning on the dashboard
• Audible alert or beep
• Vibration through the steering wheel or seat

Braking

If you don't respond to the warning, the system brakes automatically:

• Pre-charging: Gets brakes ready for maximum effectiveness
• Partial braking: Applies some brake pressure
• Full emergency braking: Maximum braking force to avoid collision

Types of AEB Systems

Limitations of AEB

AEB is a driver aid, not a replacement for attention. It has limitations:

• High speeds: Less effective above 50 mph
• Weather: Rain, fog, and snow can affect sensors
• Dirty sensors: Must be kept clean to work properly
• Unexpected situations: May not detect every hazard
• Pedestrians at night: Harder to detect in darkness

Important: Never rely solely on AEB. Always pay attention and be ready to brake yourself.

How Effective Is AEB?

Research shows AEB significantly reduces accidents:

• Euro NCAP: Cars with AEB have 38% fewer real-world rear-end crashes
• Pedestrian crashes: Reduced by up to 40%
• Insurance claims: Lower injury claims for AEB-equipped vehicles

Is AEB Mandatory?

AEB is now required on new cars:

• July 2024: All new cars sold in the EU must have AEB
• UK: Following similar requirements post-Brexit
• Euro NCAP: Cars can't get 5 stars without AEB

Most new cars since 2018 have AEB as standard or an option.

AEB and Insurance

Having AEB can affect your insurance:

• Some insurers offer discounts for safety features
• Lower accident rates mean lower risk
• But repair costs are higher if sensors are damaged

Does Your Car Have AEB?

To check if your car has AEB:

• Check the owner's manual
• Look in the safety settings menu
• Check the spec sheet or window sticker
• Contact the manufacturer

Common names for AEB include:

• Pre-Collision System (Toyota)
• City Safety (Volvo)
• Forward Collision Warning with Auto Brake (various)
• Collision Mitigation Braking (Honda)

AEB is just one of many modern safety features. Learn more about other systems in our guide to advanced driver assistance systems (ADAS).

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