The feature only works well in one specific scenario.
Automatic emergency braking (AEB) is said to be one of the most valuable safety technologies, successfully helping to prevent many rear-end collisions. But the feature has its limitations according to the latest tests from AAA.
The first AEB systems started appearing in the mid-2000s on luxury models but have rapidly expanded to lower segments since then - even the $15,580 Nissan Versa S has AEB equipped as standard. Although AAA found that the system still works well at slower speeds, it is much less effective at higher speeds or when trying to detect moving vehicles in its path at intersections. More worryingly, AAA's findings were based on tests of some of America's most popular SUVs.
Depending on the vehicle, AEB works by using radar, cameras, LiDAR, or even a combination of these to identify an imminent collision and apply the brakes to stop a crash in the first place. If that isn't possible, AEB often reduces the severity of a rear-end crash.
However, AAA argues that two common deadly crashes - T-bones and left turns in the path of oncoming vehicles - as well as rear-end collisions at higher speeds, expose the vulnerabilities of AEB. From 2016 to 2020, T-Bones and left-turn crashes in intersections caused 39.2% of fatalities involving two vehicles.
Therefore, AAA evaluated both these intersection crashes and the performance of AEB in averting rear-end collisions at speeds of 30 and 40 mph, instead of the mandated speeds of 12 and 25 mph. The rear-end tests were conducted when approaching a stationary vehicle.
Starting with the 30-mph test, AEB prevented a rear-end collision 17 out of 20 times, or 85% of the time. When a crash did occur, the speed of impact was lowered by 86%. Clearly, the system works very well under these specific conditions. When the speeds were increased to 40 mph, however, only six of 20 test runs avoided a rear-end crash - that's a success rate of only 30%. At this speed, the impact speed was reduced by 62%.
Even more concerning is what happened with the T-bone and left-turn in front of oncoming vehicle tests. Here, AEB was unable to warn the driver, slow the car down, or avoid the crash. So even though the cameras and sensors are there, they simply can't adapt to the different scenarios posed by these tests.
AAA's findings come just a few weeks after General Motors recalled 80 self-driving taxis after it was found that they could incorrectly predict the path of an oncoming vehicle, and also when performing a left turn. A software update was promised to correct the issue, but it underlines that more can be done to protect occupants from this exact crash scenario.
"Automatic emergency braking does well at tackling the limited task it was designed to do," said Greg Brannon, director of AAA's automotive engineering and industry relations. "Unfortunately, that task was drawn up years ago, and the regulator's slow-speed crash standards haven't evolved."
Brannon called for testing requirements to be updated and for "more realistic speeds" to form part of the requirements.
For the purposes of its tests, AAA used four 2022 SUVs that sell in high numbers in the USA: Chevrolet Equinox LT, Ford Explorer XLT, Honda CR-V Touring, and Toyota RAV4 LE. The agency did not rate how the vehicles performed individually, but it appears that all of them were disappointing in all but the low-speed rear-end test. AAA said that all vehicles were serviced at dealerships to ensure that their AEB systems were functioning optimally.
Linked to AEB's limitations is a study earlier this year which found that many drivers don't understand how adaptive cruise control works, and too many are lulled into a false sense of security that these systems can protect them from more hazards than they actually can.
In 2022, despite great advances in vehicle safety, it's best to treat driver-assist aids as a last resort to avoiding a collision - the best safety feature is still an attentive driver.