Pedestrian-focused automatic emergency braking (AEB) systems are becoming increasingly ubiquitous on new vehicles, as the presence of advanced driver assistance system technology continues to grow. However, according to a new study from the Insurance Institute for Highway Safety (IIHS), AEB still has shortcomings that need to be addressed before it can be considered truly safe in all conditions, including dark or poorly-lit driving situations.

Looking at crash data involving vehicles equipped with and without AEB systems, the IIHS study found that 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. Injury crash rates were 30% lower. However, when the 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 systems installed.

“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,” said 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.”

In 2019, AEB technology was only available on three out of five vehicles the Institute tested for its annual safety awards, and only one in five earned the highest rating of superior. Two years later, pedestrian AEB is available on nearly 90% of model year 2021 vehicles, and nearly half of the systems tested earned superior ratings from IIHS.

As a result of Cicchino’s research, IIHS says it plans to implement a nighttime AEB test and will publish results and pedestrian crash prevention ratings later this year.

“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.”

Vehicle vs. pedestrian crashes have been a problem for many years. Pedestrian crash deaths have risen 51% since 2009, and the 6205 pedestrians killed in 2019 accounted for nearly a fifth of all traffic fatalities. That same year, around 76,000 more pedestrians sustained nonfatal injuries in crashes with motor vehicles.

Pedestrian AEB systems were designed to reduce or mitigate such crashes. The technology warns drivers when they’re at risk of hitting a pedestrian and applies the brakes if necessary to avoid or reduce the damage of a crash.

To determine how big an impact the technology is having, Cicchino looked at nearly 1500 police-reported crashes involving a variety of 2017-2020 model-year vehicles from different manufacturers.

Accounting for the quality of vehicle headlights as well as driver age, gender, and other demographic factors, she compared pedestrian crash rates for identical vehicles with and without pedestrian AEB. Finally, Cicchino examined the impact of the technology by crash severity, light condition, speed limit, and whether the vehicle was turning.

Overall, pedestrian AEB helped reduce pedestrian crash rates of all severities by 27% and injury crash rates by 30%. However, among the subset of nearly 650 crashes for which detailed information about the lighting conditions, speed limit, and configuration of the crash was available, a more complex picture emerged.

The details of the results showed that pedestrian 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. However, in dark or unlighted areas, there was no difference in the odds of a nighttime pedestrian crash for vehicles equipped with and without the AEB crash avoidance technology.

Similarly, pedestrian AEB was associated with 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. No reduction was found on roads with speed limits of 50 mph or higher, or when a vehicle was turning.

IIHS is already examining this issue beyond studying past crash data. Recently, Aylor’s team conducted a series of research tests to help design the planned nighttime pedestrian AEB evaluation. Those tests provide additional evidence that today’s pedestrian AEB systems don’t work as well in the dark as they do in daylight.

“Some systems worked much better than others in the dark, but there was no single type of technology that got better results,” Aylor said.

For the research tests, eight small SUVs made by eight manufacturers were put through the IIHS standard vehicle-to-pedestrian evaluation in full darkness on the covered track at the Institute’s Vehicle Research Center. Each vehicle was tested twice—first with its high-beam headlights on and then with its low beams.

The test vehicles were a 2019 Subaru Forester, 2019 Volvo XC40, 2020 Honda CR-V, 2020 Hyundai Venue, 2021 Chevrolet Trailblazer, 2021 Ford Bronco Sport, 2021 Toyota C-HR, and 2022 Volkswagen Taos.

The sample included vehicles equipped with AEB systems using a single camera, a dual camera, a single camera and radar, and radar only. It also included vehicles that earned 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.

Except for the radar-only equipped Taos, performance generally declined enough in the dark to lower vehicle ratings from superior to advanced using their high beams, and from superior to basic using their low beams, according to the scoring system developed for the daytime ratings. But the benefits of radar varied in this small sample of vehicles.

As expected, the Taos achieved essentially the same results in the dark, since radar does not depend on light. However, it was also the worst performer in the daytime test.

The best performers in the nighttime tests—the C-HR and Bronco Sport—both use a combination of camera and radar. The Forester and Trailblazer, the only vehicles with camera-only systems and no radar, achieved similar nighttime results to three other vehicles with camera-and-radar systems, the CR-V, XC40, and Venue.

The tests also did not show a clear association between good headlights and higher nighttime scores. On average, vehicle AEB systems with good and acceptable headlights showed similar declines in performance in the dark, compared with their daytime results. The two worst performers in the low-beam test, the CR-V and XC40, both had good-rated headlights. The C-HR, which was tested with both good and poor headlights, outperformed all the others using its low beams, even when equipped with poor headlights.

“The better-performing systems are too new to be included in our study of real-world crashes,” Aylor said. “This may indicate that some manufacturers are already improving the nighttime performance of their pedestrian AEB systems.”