Virtually all drivers and passengers have felt the discomfort of traveling towards oncoming traffic with blinding headlights, and many will have wondered, what does United States law say about how bright a vehicle’s headlights are allowed to be? This issue is more prevalent now that LED lights are becoming increasingly popular. Thanks to a letter from the Soft Lights Foundation that was answered by the NHTSA, we now have the answer.
Can a vehicle’s headlights be too bright, according to the law?
The answer to the question about how bright a vehicle’s headlights are allowed to be is a super long one, and it’s detailed in a 122-page section of the Code of Federal Regulations (Title 49 Subtitle B Chapter V Part 571 Subpart B § 571.108).
Luckily, acting Chief Counsel at the time for the NHTSA (National Highway Traffic Safety Administration), John Donaldson, summarized the information in a letter in February 2024. His reply came in response to a letter drafted by Mark Baker, the president and founder of the Soft Lights Foundation. The foundation is a non-profit organization based in Oregon that advocates for safety standards for LED (light-emitting diode) lights.
The original letter is not available, but it’s clear from Donaldson’s response that the query involved the legality of motor vehicles fitted with LED headlights and the NHTSA’s stance on whether they pose a risk in terms of “eye safety, mental safety, and visual performance.”
NHTSA says LED headlights are illegal only under one condition
Donaldson’t reply is centered on whether the headlights are the originals fitted by the manufacturer, or if the individual bulbs have been replaced. It was also noted that headlamp requirements are based on the entire system—the lens, reflector, and light source—not the light source on its own. The bulbs are allowed to be replaced, but only if they meet specific requirements. They may not be LEDs, though.
Donaldson explained:
“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.”
In summary, LED headlights are legal if they are the ones fitted by the manufacturer. The manufacturers have standards of their own to comply with before being allowed to install them. What’s not legal is replacing bulbs with any LED bulbs, so if you’ve fitted LED bulbs yourself, then you may be breaking federal law.
Why are LED headlights so popular?
LED headlights have been growing in popularity and prevalence in the automotive industry for years. In 2018, 55% of vehicles were fitted with LEDs. In 2021, the percentage of cars using LED headlights globally was above 60%, and 90% in electric vehicles (EVs).
There’s a wide variety of aftermarket LED products available to drivers who want to personalize their vehicles, such as those providing different levels of brightness, color or temperature tints, and beam patterns. It’s these options that are illegal in the United States.
What are the advantages of LED headlights?
There are several advantages of LEDs, including increased energy efficiency, which is a focus in terms of renewability. They also have longer lifespans than traditional halogen headlamp bulbs and offer better illumination.
When it comes to demonstrable safety records, statistics show a 19% drop in nighttime single-vehicle crashes and a 23% decrease in after-dark pedestrian-involved accidents. This proves that LED lights offer a superior quality of illumination.
However, the benefit of improved illumination, and therefore visibility, for drivers of the vehicles fitted with LEDs doesn’t apply to instances where the LED lights are so bright to the extent that they hamper other drivers’ ability. This risks the safety of other road users and it’s the question that the Soft Lights Foundation wanted definitively answered.