Too Bright Headlights Aren't to Blame for more Accidents

Arlington VA October 16, 2025 The IIHS reported that complaints that today’s headlights are more likely to blind oncoming drivers have gotten louder in recent years. But glare is implicated in just a tiny fraction of nighttime crashes, and that percentage has hardly changed over the past decade, a new study from the Insurance Institute for Highway Safety shows.

“Although it can certainly be uncomfortable, headlight glare contributes to far fewer crashes than insufficient visibility,” IIHS President David Harkey said. “But that doesn’t mean reducing glare isn’t an important goal — one that we’ve long focused on at IIHS in addition to improving illumination.”

From 2015 to 2023, headlight glare was cited as a factor in only one or two out of every thousand nighttime crashes across 11 U.S. states, the new study shows. And while the amount of light given off by headlights increased over this period — slashing crashes caused by poor visibility — there was essentially no change in how often glare was mentioned in crash reports.

Headlight design shift

While federal headlight standards for minimum and maximum brightness have not changed since 1997, the headlight rating program IIHS began in 2016 has helped to drive a shift in headlight design in the U.S. fleet.

The Institute’s ratings are technology-agnostic. But, in general, the program has led manufacturers to use LED headlamps on more models. The story is more complicated than that, though, because the IIHS ratings penalize headlights whose low beams produce excessive glare that can temporarily blind oncoming drivers. By factoring in both visibility and glare, IIHS ratings have led automakers to pay attention to headlight aim.

Manufacturers have adapted. When the Institute released its first headlight ratings in 2016, only one out of more than 80 headlight systems evaluated received a good rating, compared with about 51% of the headlights IIHS tested on model year 2025 vehicles. There have been similar increases in acceptable ratings. Only about 16% of the headlights tested today are rated marginal or poor, compared with 82% in 2016.

Those changes have resulted in a dramatic reduction in crashes that occur due to poor visibility. A previous IIHS study of police-reported crashes showed that vehicles with good ratings for visibility in the IIHS headlight test are involved in 19% fewer nighttime single-vehicle crashes and 23% fewer nighttime pedestrian crashes than vehicles with poor-rated headlights.

The effects of different levels of glare are harder to isolate. Most glare-related crashes are cases in which the driver affected by the glare runs off the road. The glare-producing vehicle isn’t involved in the crash and thus can’t be identified. There’s no way to know how its headlights perform in IIHS tests or whether the driver neglected to switch from the high beams to low beams.

For this reason, the new study approaches the issue differently, looking at how often glare is cited as a factor in crashes and how that has changed as headlight ratings have improved.

Tracking glare in crash reports

IIHS Principal Research Engineer Matthew Brumbelow examined data from 11 states in which police can list glare as a contributing factor in crash reports. Because only two of those states distinguish between glare caused by the sun and glare caused by the headlights of an oncoming vehicle, he looked specifically at crashes with glare that occurred at night.

Out of around 24 million total crashes, fewer than 150,000 had glare coded as a contributing factor, and a far smaller fraction were both coded for glare and occurred at night. With a few exceptions, these nighttime glare crashes accounted for only one or two out of a thousand crashes per year in all 11 states.

Moreover, while this glare rate ticked up and down a little, it remained relatively constant over the study period and certainly did not show a steady increase coinciding with the improvement in IIHS headlight ratings. In fact, the glare rate was highest in 2015 and lowest in 2020.

Relative to crashes without reported glare, crashes with glare were more often single-vehicle crashes, occurred more frequently when it was raining or the road surface was wet, and happened more often on local, undivided, two-lane roads with relatively low speed limits. In addition, drivers in crashes with reported glare tended to be older in age and driving older vehicles.

“Drivers older than 70 seem to be most affected by headlight glare, while those between 55 and 60 don’t appear to have an increased crash risk,” Brumbelow said. “It’s also possible that the better visibility that newer vehicles provide for their own drivers provides some defense against glare from oncoming headlights, in the way that other people’s headlights don’t seem as bright during the day.”

Opportunities for improvement

Along with improving the visibility provided by headlights, automakers have made progress in reducing the amount of glare their headlights produce. In IIHS testing, 21% of the headlights available on 2017 models produced excessive glare. For 2025 models, this percentage dropped to just 3%. In the Institute’s scoring system, excessive glare makes it impossible to earn a good or acceptable rating.

That doesn’t mean manufacturers and safety professionals should not be working to reduce glare further or mitigate its effects, however. Glare can be disconcerting to some drivers, even at levels that don’t exceed the IIHS tolerances. Moreover, people with age-related macular degeneration and other health conditions can be especially sensitive to bright lights.

One way to address that problem is to focus on preventing the crash types associated with glare. Reducing lane departures — with improved lane markings and in-vehicle lane departure warning and prevention features, for example — could cut the already small number of glare-related crashes by more than half.

High-beam assist, which automatically switches from high beams to low beams when there are vehicles ahead, could mitigate the problem of drivers neglecting to do so manually. The IIHS rating program awards bonus points for this feature.

Adaptive driving beam headlights are another promising development. These systems adjust the headlight beam pattern to dim only the portions directed at other vehicles while maintaining full high-beam illumination otherwise.

Unfortunately, regulatory hurdles have delayed their adoption in the U.S., and no vehicles in the U.S. market were equipped with adaptive driving beam headlights as of the end of 2024. Although the National Highway Traffic Safety Administration began allowing such systems in 2022, arcane differences between the U.S. standards and those applied in Europe — where adaptive driving beams have been common for more than a decade — continue to slow the rollout of the technology here.

“We’d like to see these obstacles to adaptive driving beams removed, but the IIHS headlight rating program is already driving advancements that are making nighttime driving safer, both by improving visibility and by reducing glare,” Harkey said.