Can headlights be too bright?
CLARKSBURG, W.Va. (WBOY/NEXSTAR) — It's something many drivers have no doubt experienced during the wintertime. You're driving at night when you're seemingly blinded by a pair of LED headlights. You might wonder if there's a limit on how bright headlights can be, or even how headlights that bright are legal in the first place.
The answer to that question is a very long one—about 122 pages long to be exact, and it can be found in Title 49 Subtitle B Chapter V Part 571 Subpart B § 571.108 of the Code of Federal Regulations.
Luckily, the answer was summed up in a letter written by then Acting Chief Counsel for the National Highway Traffic Safety Administration (NHTSA) John Donaldson in February 2024.
The letter is a response to an inquiry made by Mark Baker, the founder and president of the Soft Lights Foundation, a registered 501(c)(3) non-profit based in Oregon that advocates for safety standards on LED lights. Although Baker's original letter to the NHTSA is not available, the response suggests Baker was asking if LEDs are legal as a light source in motor vehicle headlamps and if the NHTSA believed LED headlamps posed a risk to “eye safety, mental safety, and visual performance."
Donaldson's response shed light on the legality of LED headlights stating that they might be illegal after all.
Donaldson explained in his letter to Baker that headlamp requirements are based on the entire system, i.e. the lens, reflector, and light source, not the light source on its own. Headlamp bulbs can be replaced, but only if the bulbs meet the specific requirements.
"While LED light sources that are part of an integral beam headlamp are permitted [...], no LED light source is currently permitted to be used in a replaceable bulb headlamp," Donaldson wrote.
So, LEDs are allowed in headlamp systems designed by car manufacturers but are not approved as replacement bulbs. What that means is if you changed out your own car's headlights with replaceable LED bulbs, you might be breaking federal law.