Headlights are too bright! But US experts say they’re not bright enough | Well actually | The Guardian

Driver complaints about high beams are commonplace, though specialists say US roads need to be better lit

A few weeks ago, I was driving along a dark road at night. Suddenly, I couldn’t see. The headlights of the cars behind and ahead of me were, by my most conservative estimate, as bright as the surface of the sun. For a few seconds, I was blinded. I managed to pull over and waited for my vision to return.

Complaints about the brightness of modern headlights have become commonplace. On X, thousands of users have tweeted about headlights being too bright. The subreddit r/fuckyourheadlights has over 35,000 members who post blurry photos of offending high beams and LED headlights. Outlets like the New York Times and NBC News have written about the risks of headlight glare. Advocacy groups have called for bans on LED headlights. And the UK government launched a review into the dangers of headlight glare earlier this year, after many driver complaints.

And yet, according to many experts, the problem with headlights is not that they’re too bright – it’s that they’re not bright enough.

“We actually need more light on the road than what we have,” says Greg Brannon, director of automotive engineering at the American Automobile Association (AAA). Only a minority of US roadways have overhead street lighting, as one 2019 AAA report noted. As a result, in many areas, headlights are the sole method of illumination when driving at night.

But which is the safety bigger risk: inadequate illumination, or headlights that impair the vision of other drivers?

Driving at night is significantly more dangerous than driving during the day.

“When adjusted for distances traveled, the fatality rate [of driving] at night is two to four times higher than during the daytime,” says Dr Joanne Wood, a professor in the school of optometry and vision science at the Queensland University of Technology who specializes in vision and driving. One reason is that there tend to be more incidents of drunk and fatigued driving at night. The more common reason is it’s simply harder to see at night.

Wood says low light levels leading to poor visibility “is the leading cause of collisions with pedestrians, cyclists and other low-contrast obstacles at night-time”.

But glare from oncoming headlights can also reduce drivers’ ability to recognize road hazards like pedestrians. It can disturb a driver’s visual function and result in temporary “blindness”, she says, and also affect the visibility of other objects due to intraocular light scatter, or the scattering of light within our eyes, which reduces the contrast of objects close to the light source.

“Some objects that are visible when no glare is present become difficult to see when there is [glare],” Wood explains.

Although headlights feel significantly brighter than they used to, Brannon notes that the maximum standards for light output set by the US transportation department’s National Highway Traffic Safety Administration (NHTSA) haven’t changed in decades. Not only that, the US maximum light output for a vehicle is significantly lower than in other countries: 150,000 candela (a measure of luminous intensity) compared to 430,000 candela in Europe.

While the candela measure hasn’t changed, there are other relevant factors. “Brightness is measured in a variety of different ways,” Brannon says.

Part of the issue, he says, is that the temperature of the light in headlight bulbs has changed. Brannon drives a 1957 Volkswagen built with incandescent bulbs. These were the norm until halogen headlights took over in the 1980s, then LEDs in the 2010s.

Incandescent and halogen bulbs typically emit a light that has a light orange or red hue, which is gentler on the eye. LEDs tend to emit a harsh white light. Brannon says the headlights of his Volkswagen create a “nice amber glow about 5ft in front of the car” – warm and welcoming, but not great for fully illuminating the road ahead.

Experts point out that more drivers are buying bigger cars. Because these cars are taller, their headlights are more likely to shine in the eyes of drivers of smaller cars. One 2021 report found that in the US, SUVs and crossover vehicles made up roughly 50% of vehicle purchases, and sales of pickup trucks roughly 20%.

Additionally, many vehicles on the road have misaligned headlights. Over time, the regular wear and tear of driving can jostle headlights out of alignment, meaning the brightest part of the light ends up illuminating areas it’s not supposed to – say, right into an oncoming driver’s eyes. One NBC News report found that “only 15 states require annual or biennial passenger vehicle inspections”, and only 10 of those check headlight alignment.

The glare from LED headlights has a particularly strong effect on drivers with conditions that lead to light sensitivity. Mark Baker is president of the Soft Lights Foundation, a non-profit aimed at “protecting people and the environment from the harms” of LED headlights.

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Baker, who was diagnosed with mild autism, says the advent of LED headlights has been “devastating” to him. “They were overwhelming my nervous system,” he says. He founded Soft Lights in 2016, and since then, the group has petitioned the FDA, the Department of Energy, the Federal Highway Administration and other government agencies to regulate LED light sources.

In 2022, NHTSA announced it would allow US car manufacturers to install adaptive driving beam headlights, a technology already widely used across Europe.

Many headlights in the US are equipped to automatically switch from high to low beams when another car is ahead of them. But adaptive headlights are equipped with a complex array of sensors and LED lights, explains David Aylor, vice-president for active safety testing at the Insurance Institute for Highway Safety. When the system’s camera senses a vehicle or pedestrian approaching the front of the car, only the potentially disruptive sections of light switch off or dim.

This means a driver with adaptive headlights can use high beams all the time. The system just “shutters light for anybody or anything that shouldn’t be illuminated”, Brannon says. According to a 2019 AAA report, headlights increased roadway lighting by as much as 86% compared to US headlights without the adaptive beam technology.

And yet, no adaptive high beams have been installed in the US since the NHTSA approved the technology. The US and Europe have different lighting and testing standards, and Aylor says it’s a struggle for manufacturers to meet US standards as well as afford the more complex lighting systems.

Some are skeptical that adaptive headlights are really a panacea. Baker calls the technology a “scam” and says research has shown the lights aren’t yet effective at sensing other cars on hills or during turns. If the sensors toggle from high beam to low beam, that’s still too bright for most people’s eyes, he argues. “It’s too intense, and it’s too blue,” he says.

But Brannon says adaptive headlights are promising and that AAA has lobbied extensively for them. The group is also researching other ways to make headlights less harsh.

“Is it possible that we could provide the same level of illumination with a color that is more human friendly?” he says. “We don’t know the answer to that yet.”

I tell him about my recent scare on the road, and ask him what drivers should do when bright headlights are coming at them.

“Don’t look at the light source,” he says.

This article was amended on 2 November 2024 to correct the spelling of Greg Brannon’s surname.