Headlights have gotten much better at lighting the road ahead in recent years, but glare-related crashes have not increased. That finding is in sharp contrast to complaints from motorists who say the upgraded headlights are more likely to blind oncoming drivers. Glare is implicated in a small fraction of nighttime crashes, but that percentage has not changed much over the past decade.
Those are a few of the highlights of a new study released on Wednesday by the Insurance Institute for Highway Safety (IIHS), a nonprofit financed by the insurance industry, that looked at how often glare is cited as a factor in crash reports and how that has changed as headlight ratings have improved due to design advancements.
“Although it can certainly be uncomfortable, headlight glare contributes to far fewer crashes than insufficient visibility,” David Harkey, the Insurance Institute’s president, said in a statement. “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.”
Federal headlight standards for brightness have not changed since 1997, but the Insurance Institute’s headlight ratings program, the safety group said, “helped to drive a shift in headlight design in the U.S. fleet,” since it began in 2016. The program it said, have helped make nighttime driving safer by improving visibility and reducing glare. For example, ratings penalize manufactures whose low beams produce excessive glare that can temporarily blind oncoming drivers.
Matthew Brumbelow, the study’s author and the Insurance Institute’s principal research engineer, examined data from 11 states in which police can list glare as a contributing factor in crash reports.
In the study, which examined some of six million nighttime crashes over an eight year period from 2015 to 2023, headlight glare was cited as a factor in only one or two out of every thousand crashes. And while the amount of light given off by headlights increased over this period, lowering the number of crashes caused by poor visibility, there was “essentially no change in how often glare was mentioned in crash reports,” according to the report.
Crashes with glare often occurred more frequently when it was raining or the road surface was wet; on local, undivided, two-lane roads with relatively low speed limits; in collisions involving a single vehicle; and among drivers who were older and drove older vehicles.
Along with improving the visibility provided by headlights, automakers have made progress in reducing the amount of glare their headlights produce, researchers said, but manufacturers and safety professionals should work to reduce glare further or mitigate its effects.
Several “promising developments,” they added, could reduce the number of glare-related crashes even further. These include:
- preventing crash types associated with glare by improving technology like lane departure warning and prevention systems;
- implementing high beam assist, which automatically switches from high beams to low beams when there are vehicles ahead, as drivers can neglect to do so manually; and
- installing adaptive driving beam headlights that adjust the headlight beam pattern to dim only the portions directed at other vehicles, while maintaining full high-beam illumination. Regulatory hurdles have delayed the adoption of this safety feature in the U.S., and no vehicles in the domestic market were equipped with it as of the end of 2024, researchers said. In Europe, the technology has been common for more than a decade, but differences between the U.S. and European standards continue “to slow the rollout” in the U.S., they added.
“We’d like to see these obstacles to adaptive driving beams removed,” Harkey said.
For more information about the study, click here.
