AAA finds automatic brakes don't stop crashes

20 makers have pledged to make automatic braking standard by 2022

Published: October 5, 2016, 9:30 PM
Updated: December 7, 2016, 5:49 PM

Volvo Automatic Emergency Braking

The American Automobile Association (AAA) has conducted a series of tests on automatic emergency braking systems and found that their performance varies widely.

Automatic braking is a technology that automatically applies a vehicle’s brakes in an emergency, if the driver does not take action to apply the brakes (perhaps because he’s been incapacitated in some way). Earlier this year, 20 automakers (Audi, BMW, FCA, Ford, GM, Honda, Hyundai, Jaguar Land Rover, Kia, Maserati, Mazda, Mercedes-Benz, Mitsubishi, Nissan, Porsche, Subaru, Tesla, Toyota, Volkswagen and Volvo) agreed to make the technology standard equipment on their US-bound cars.

Currently, the systems are available on more than half of all new cars, but standard on just 10%.

Current systems, though, don’t always stop the vehicle completely. Nor can they in some instances, depending on the speed of the vehicle and weather conditions. Rather, manufacturers tend to work toward slowing the car down dramatically in order to lessen the severity of the crash — a procedure known as crash mitigation.

“AAA found that two-thirds of Americans familiar with the technology believe that automatic emergency braking systems are designed to avoid crashes without driver intervention,” said John Nielsen, AAA’s managing director of automotive engineering and repair. “The reality is that today’s systems vary greatly in performance, and many are not designed to stop a moving car.”

AAA partnered with the Automobile Club of Southern California's Automotive Research Center to test 5 such systems, available on different 2016 cars. For comparison’s sake, the systems were compared according to whether they are designed to prevent a crash or just mitigate it.

Naturally, the systems designed to stop the vehicle completely have a speed threshold above which they can only slow the vehicle anyway. Of those vehicles that could stop the car completely, 60% of them did so from 50 km/h, although one third of vehicles with systems meant to mitigate a crash also stopped completely.

"When traveling at 30 mph, a speed reduction of just 10 mph can reduce the energy of crash impact by more than 50%," said Megan McKernan, manager of the Automobile Club of Southern California’s Automotive Research Center.

At speeds above those recommended by the manufacturer (and also above federal requirements), systems designed to stop the vehicle reduced speed by 74% and avoided crashes 40% of the time. Those systems designed to just lessen the severity of a crash reduced speed by just 9%.

Overall, the tests found that vehicles with crash prevention braking lessened a vehicle’s speed by 79% on average, whereas those with crash-mitigation scrubbed off only 40%.

The association advises drivers to know what their vehicle’s systems are meant to do, and not rely on them to prevent a crash.