NHTSA Targets Blinding Headlight Glare in New Safety Push
Federal regulators are beginning a review of U.S. vehicle lighting standards to address complaints about headlight glare and evaluate newer technologies designed to improve nighttime visibility. The National Highway Traffic Safety Administration is examining Federal Motor Vehicle Safety Standard No. 108, including headlight intensity, aim, mounting height and testing requirements.
NHTSA targets outdated lighting standards
NHTSA said current lighting standards may not adequately account for modern headlamp designs or the factors that contribute to glare for other road users. The agency plans to consult with automakers, safety advocates, lighting engineers, human-vision researchers and other technical experts.
The effort is being conducted through a negotiated rulemaking process. NHTSA described it as its first negotiated rulemaking related to vehicle lighting in more than 25 years. The agency has not established a timeline for issuing a final rule.
“Today’s standards do not allow automakers to deploy the latest safety-improving lighting technologies, so we are bringing key experts and stakeholders together to modernize our standards and address potential causes of glare,” NHTSA Administrator Jonathan Morrison said.
Glare, intensity and vehicle design
NHTSA’s review will consider how modern lighting technology, vehicle height and headlamp aim affect glare. The amount of light reaching another driver’s eyes depends on the intensity and direction of the beam, rather than simply the total number of lumens produced by a headlamp.
According to NHTSA research on nighttime glare and driving performance, an oncoming headlamp intensity of 1,000 candela can reduce a driver’s visibility distance by about one-third. At 7,000 candela, visibility distance can be reduced by approximately two-thirds.
The agency’s review also includes lower-beam photometry, which measures how headlamp light is distributed. Officials have not proposed a specific brightness limit, and it remains unclear what changes could ultimately be included in a revised standard.
Adaptive beam technology under review
In February 2022, NHTSA issued a final rule allowing adaptive driving beam headlights on new vehicles. The systems are designed to adjust portions of the high-beam pattern, reducing light directed toward occupied areas of the roadway while maintaining illumination in other areas.
NHTSA’s current review could further clarify the regulatory path for adaptive lighting and other technologies intended to improve visibility without creating excessive glare. The agency is also examining whether existing testing methods adequately reflect differences in vehicle height, headlamp placement and real-world road conditions.
Research shows glare is not limited to nighttime
The Insurance Institute for Highway Safety has reported that modern vehicle headlights are generally brighter than those used in the past. IIHS research also found that vehicles receiving stronger headlight visibility ratings are involved in fewer crashes.
More than 90% of glare-involved crashes in the institute’s research occurred during daylight hours. The findings indicate that glare can result from the sun as well as vehicle lighting, depending on the direction and intensity of light reaching a driver’s eyes.
NHTSA’s announcement begins a research and recommendation process. Any changes to FMVSS 108 would require additional regulatory action before new requirements could take effect.
