How much safer is automatic emergency braking? IIHS finds out

Does automatic emergency braking (AEB) help cars avoid crashes at higher speeds? The Insurance Institute for Highway Safety (IIHS) reports that, like your mileage, your crash results may vary.

A new study released Thursday found that increased speeds diminished the efficacy of stopping in nine out of ten popular crossover SUVs tested by the nonprofit safety agency. Only the Subaru Forester earned top “Good” ratings on the tougher tests. 

The Toyota RAV4 and Honda CR-V, two of the bestselling non-trucks in America, earned “Acceptable” ratings at stopping before rear-ending an inflatable test car at speeds of 31, 37, and 43 mph. Until now, the IIHS had only conducted emergency stopping tests at 12 mph and 25 mph. 

“This is a vital update to one of our most successful test programs,” IIHS President David Harkey said in a statement. “This new, tougher evaluation targets some of the most dangerous front-to-rear crashes that are still happening.”

2024 Subaru Forester stops during IIHS high-speed AEB test

Automatic emergency braking effectiveness at low speeds

Traffic crash data culled by the IIHS suggests that cars equipped with automatic emergency braking prevent about half of all rear-end collisions, which is the most common type of crash. The technology could prevent an estimated 42,000 rear-end crashes annually.

It’s one of the reasons why the automotive industry agreed to and delivered on equipping 95% of new passenger cars sold with the life-saving technology by 2023. The volunteer agreement was brokered by the IIHS, Consumer Reports, the NHTSA, and other consumer safety advocates. All vehicles tested by the IIHS at the slower speeds had earned “Superior” ratings in 2022, prompting the IIHS to raise the automatic emergency braking safety bar. 

The IIHS enhances its safety criteria whenever the vast majority of cars tested begin acing the tests. It’s how the insurance-industry funded organization keeps its coveted Top Safety Pick+ and Top Safety Pick awards vital to car shoppers and crucial to automotive marketers.

The 2024 Top Safety Pick recipients had to earn “Good” ratings on an updated side-impact test traveling at faster speeds and with a heavier strike vehicle. That represents the market’s shift from cars to SUVs and for vehicles moving faster than in the two decades since the last time those tests were implemented. Advanced headlight tests were also employed, since most traffic fatalities happen at night. 

Usually, the IIHS implements a new test for a year or two before it becomes part of TSP criteria to give automakers time to reach compliance. The IIHS has not disclosed when or how the new AEB tests will be part of the TSP awards. 

IIHS automatic emergency braking tests at high speed and motorcycles

IIHS automatic emergency braking tests at high speed and motorcycles

IIHS automatic emergency braking tests at high speed and motorcycles

Automatic emergency braking effectiveness with motorcycles

Not only has the IIHS implemented the three higher speed tests, it has begun to test the efficacy of AEB with rear-end collisions of motorcycles and swerving to miss a rear-end collision with semi trucks. 

“Obviously, crashes that happen at higher speeds are more dangerous,” said IIHS Senior Research Scientist David Kidd, who led the study. “Deadly underride crashes often occur when the struck vehicle is a large truck, and motorcyclists are frequently killed when they’re rear-ended by a passenger car, since their bike offers no protection from the impact.”

To come up with the new rating, the IIHS conducted multiple trials of the three tests, one for the inflatable passenger car, a second with the torso of a dummy astride an inflatable motorcycle, and the third with an actual semi trailer. There are various thresholds and factors in the assessment, and likely lead to why automakers set collision warning alerts at certain volumes in the car, and at certain speeds and distances. 

2024 Ford Escape fails to stop during IIHS high-speed AEB test

Automatic emergency braking effectiveness at high speeds

The Subaru Forester, for instance, fully braked at all three speeds without contacting the passenger car target, and avoided hitting the motorcycle target in all but the 43-mph test. It slowed by 30 mph, however. In all three tests, the audible warnings sounded at least 2.1 seconds before impact with the trailer, enabling the human driver to swerve out of its way. In “Poor” rated vehicles, the vehicles hit either the passenger car or motorcycle, or didn’t allow enough time (at least 2.1 seconds) to miss the trailer. 

Here’s how the ten vehicles rated. 

2024 Subaru Forester: “Good”

2024 Honda CR-V: “Acceptable”

2024 Toyota RAV4: “Acceptable”

2024 Ford Escape: “Marginal”

2024 Hyundai Tucson: “Marginal”

2024 Jeep Compass: “Marginal”

2024 Chevy Equinox: “Poor”

2024 Mazda CX-5: “Poor”

2024 Mitsubishi Outlander: “Poor”

2024 Volkswagen Taos: “Poor”