David Harkey President at Insurance Institute for Highway Safety | Insurance Institute for Highway Safety
Complaints about the brightness and glare of modern vehicle headlights have increased in recent years. However, a new study from the Insurance Institute for Highway Safety (IIHS) finds that glare is a factor in only a very small portion of nighttime crashes, and this percentage has remained steady over the past decade.
“Although it can certainly be uncomfortable, headlight glare contributes to far fewer crashes than insufficient visibility,” said IIHS President David Harkey. “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.”
The study analyzed crash data from 11 U.S. states between 2015 and 2023. It found that headlight glare was listed as a contributing factor in just one or two out of every thousand nighttime crashes. During this period, headlight brightness increased and contributed to fewer crashes due to poor visibility, but there was little change in how often glare was cited in crash reports.
Federal standards for headlight brightness have not changed since 1997. However, the IIHS headlight rating program launched in 2016 has influenced changes in headlight design. The program does not favor any specific technology but has led manufacturers to install LED headlamps on more vehicles. The IIHS rating system penalizes headlights with low beams that create excessive glare, prompting automakers to pay closer attention to headlight aim.
In 2016, only one out of more than 80 headlight systems tested by IIHS received a good rating. By model year 2025, about 51% earned a good rating, with similar improvements seen in acceptable ratings. Today, only about 16% of headlights tested are rated marginal or poor, compared with 82% in 2016.
These changes have led to a significant decrease in crashes caused by poor visibility. Previous research from IIHS found that vehicles with good-rated headlights are involved in 19% fewer nighttime single-vehicle crashes and 23% fewer nighttime pedestrian crashes compared to those with poor-rated headlights.
The study also noted that most glare-related crashes involve a driver affected by another vehicle’s headlights running off the road. The vehicle producing the glare is usually not involved in the crash and cannot be identified or assessed under IIHS testing protocols.
IIHS Principal Research Engineer Matthew Brumbelow reviewed crash data from states where police can list glare as a contributing factor. Out of roughly 24 million crashes analyzed, fewer than 150,000 were coded as involving glare, and even fewer occurred at night. In most states studied, these nighttime glare-related crashes represented just one or two out of every thousand crashes annually. The rate fluctuated slightly over time but did not show a steady increase as headlight ratings improved. In fact, the highest rate occurred in 2015 and the lowest in 2020.
The study found that glare-related crashes were more likely to be single-vehicle incidents, occur during rain or on wet roads, and take place on local, undivided two-lane roads with lower speed limits. Drivers involved tended to be older and were often 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.”
Automakers have also reduced excessive glare from headlights. In IIHS testing, 21% of headlights on 2017 models produced excessive glare; by model year 2025, this dropped to just 3%. Under IIHS scoring, headlights with excessive glare cannot earn a good or acceptable rating.
Despite progress, IIHS notes there is room for further improvement. Glare can still bother some drivers, especially those with certain health conditions or age-related vision issues. Efforts such as improving lane markings and using lane departure warning systems could help reduce glare-related crashes even further. High-beam assist technology, which automatically switches between high and low beams when other vehicles are present, can also mitigate issues when drivers forget to switch manually. IIHS awards bonus points for this feature.
Adaptive driving beam headlights offer another solution by adjusting light patterns to avoid blinding other drivers while maintaining high-beam illumination elsewhere. However, regulatory differences between U.S. and European standards have delayed their adoption domestically. As of late 2024, no U.S.-market vehicles had adaptive driving beam headlights installed.
“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.
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