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, according to a new study.
The Insurance Institute for Highway Safety (IIHS) research found that from 2015 to 2023, headlight glare was cited as a factor in only one or two out of every thousand nighttime crashes across 11 US states, despite the amount of light given off by headlights increasing over this time period.
IHS 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, 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 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.
“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.”
