How Well Do Automatic Emergency Braking Systems Work?

Nearly 2,000 people die each year in rear-end collisions, according to the National Highway Traffic Safety Administration, and automakers have turned to advanced technology to keep drivers safe.

Automatic emergency braking (AEB) is one advanced technology that is available on an increasing number of new vehicles. AEB systems can apply the brakes to avoid an imminent collision if the driver does not take action, relying on sensors and cameras to “see” traffic, pedestrians and other hazards.

Currently, AEB systems are offered as standard equipment on 10 percent of new vehicles and as an optional package on 53 percent. These numbers will grow steadily in the coming years, as automakers have committed to making automatic emergency braking systems standard on all new vehicles by 2022.

AAA conducted a test on the safety technology and found that AEB systems vary widely in how they are designed and in how they perform when a driver fails to engage the brakes.

How AAA tested the AEB systems

AAA tested five 2016 model-year vehicles equipped with AEB systems in real-world driving scenarios designed to push the technology’s limits. There are differences between each manufacturer’s AEB systems, so vehicles were grouped into two categories for the tests:

• AEB systems designed to prevent crashes

• AEB systems designed to lessen crash severity

Tests performed by other organizations have focused on vehicles traveling at speeds under 25 mph when they encounter a vehicle stopped in their path. AAA performed that same test, then extended it to higher speeds and in dynamic scenarios where vehicles were moving at different speeds. AAA also created a test scenario designed to mirror “real world” driving behavior, in which the test vehicle was cut off by a second vehicle that suddenly applied its brakes.

Four things the testing showed

After more than 70 trials, conducted with five vehicles from five manufacturers, AAA’s tests revealed:

Slow speed collisions are mostly avoidable

With speed differentials below 30 mph, systems designed to prevent crashes successfully averted collisions in 60 percent of test scenarios.

Systems designed to lessen crash severity can sometimes avoid collisions entirely

In nearly one-third of test scenarios, the systems designed to only lessen crash severity were able to completely avoid collisions.

AEB systems work at high speeds, but not well

When traveling at 45 mph and approaching a static vehicle, a scenario designed to push systems beyond their stated limitations, systems designed to prevent crashes reduced speeds by 74 percent overall, avoiding crashes 40 percent of the time. In contrast, systems designed to lessen crash severity reduced vehicle speed by only 9 percent overall.

Crash-prevention AEB systems are better at reducing speed

In terms of overall speed reduction, AEB systems designed to prevent crashes reduced vehicle speeds by 79 percent, nearly twice that of systems designed to only lessen crash severity (40 percent).

The bottom line on automatic emergency braking

AAA’s tests showed that an AEB system can be effective in limiting the severity of a crash—or avoiding a crash altogether—but not all AEB systems are created equal. AAA recommends you consider this technology when making a new vehicle purchase, but make sure you know the vehicle’s automatic emergency braking capabilities–and its limitations–before getting behind the wheel.