Automatic Emergency Braking May Leave You in the Dark — Literally

More and more drivers are clamoring for improved safety technology, but one of those systems has a recently detected flaw.

IIHS pedestrian AEB night test
IIHS noticed that automatic emergency braking effectiveness declines as it gets darker.

Automatic emergency braking systems are designed to bring a vehicle to a stop if a pedestrian walks in front of your car or the SUV in front of you slams on their brakes and you don’t react. However, a new research study by the Insurance Institute for Highway Safety says the darker it is outside, the less effective the systems are.

“This is the first real-world study of pedestrian AEB to cover a broad range of manufacturers, and it proves the technology is eliminating crashes,” says Jessica Cicchino, IIHS vice president of research and the study’s author. 

“Unfortunately, it also shows these systems are much less effective in the dark, where three-quarters of fatal pedestrian crashes happen.”

Nighttime isn’t the right time

IIHS 2019 Pedestrian test CR-V
The 2019 Honda CR-V was one of the top performers in IIHS pedestrian automatic emergency brake tests.

In all light conditions, crash rates for pedestrian crashes of all severities were 27% lower for vehicles equipped with pedestrian AEB than for unequipped vehicles, a new study from the Insurance Institute for Highway Safety found. Injury crash rates were 30% lower. 

However, when the IIHS researchers looked only at pedestrian crashes that occurred at night on roads without streetlights, there was no difference in crash risk for vehicles with and without pedestrian AEB. To better study the issue, the organization developed a test which it will begin implementing in the near term.

“The daylight test has helped drive the adoption of this technology,” said David Aylor, manager of active safety testing at IIHS. “But the goal of our ratings is always to address as many real-world injuries and fatalities as possible — and that means we need to test these systems at night.”

Conditions change as the available light dissipates, and the research shows it. AEB reduced the odds of a pedestrian crash by 32% in the daylight and 33% in areas with artificial lighting during dawn, dusk and nighttime. But in unlighted areas, there was no difference in the odds of a nighttime pedestrian crash for vehicles with and without the crash avoidance technology, IIHS noted.

Pedestrian AEB systems posted very similar results: a 32% reduction in the odds of a pedestrian crash on roads with speed limits of 25 mph or less and a 34% reduction on roads with 30-35 mph limits, but no reduction at all on roads with speed limits of 50 mph or higher or when the vehicle was turning.

IIHS AEB nighttime graphic

Finding a problem

The group began running its own tests to determine if there was actually problem — and they found it. In testing the eight vehicles, there were some differences in performance, but all of them were less effective as the light disappeared, Aylor noted.

The test group — all 2019 model year small SUVs — included vehicles with AEB systems using a single camera, a dual camera, a single camera and radar, and radar only. It also included vehicles that earn superior, advanced and basic ratings in the Institute’s daylight vehicle-to-pedestrian front crash prevention evaluation, as well as vehicles equipped with good, acceptable and poor headlights.

“Some systems worked much better than others in the dark, but there was no single type of technology that got better results,” Aylor said, adding later better-performing systems were too new to be included in the testing, which is good news. It suggests that automakers are already making improvements to the technology in this area.

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