Glaringly bright, blue-hued headlights filled my hatchback earlier this year as I drove 80 miles an hour on the highway between San Antonio and Austin. The headlights shone so brightly that their reflection in my rearview mirror burned my eyeballs, causing me to look away from the road and rapidly slow down. The large luxury SUV behind me began riding my tail — causing an even more intense glare to engulf my car — before aggressively whipping around to pass me.

For a moment, all was fine. My eyes adjusted. And I began to pick up speed again — only to be visually assaulted by a lifted truck with even brighter headlights and flood lights atop its roof, then an electric vehicle with the whitest lights I’d ever seen, and an onslaught of others. Fearing my car being slammed from behind every time I was forced to slow down and look away from the road, I got off the highway and took an alternative route.

The headlights felt like they’d become especially hard on my eyes in recent years. Maybe I was just getting old, I thought, or my eyes had been weakened by working on a computer for a living.

Then a listener of Vox’s Explain It to Me podcast named Reed called and asked, “Am I going crazy? Or does every new car on the road have the world’s brightest headlights? I’m wondering why this is suddenly happening? And are there any limits? Can people just put whatever they want on the front of their car and blind everyone else?”

He wasn’t alone. Our show has received multiple emails with similar inquiries from listeners and Vox readers. And there’s even a subreddit dedicated to the topic, where people complain, make jokes, and work together to find solutions. So in hopes of helping Reed, myself, and the many other upset drivers, Explain It to Me took on Reed’s question.

Are car headlights getting brighter?

There are two ways to answer that question, lighting scientist John Bullough, who leads the Light and Health Research Center at the Icahn School of Medicine at Mount Sinai, told Vox.

The first has to do with the color of LED lights, the kind now overwhelmingly used in car headlights. “You’ve probably noticed that a lot of them look a lot more of a bluish white compared to the yellowish white of halogen headlights,” Bullough said, which used to be more common in headlights.

The concepts we use to measure light intensity — lumen and candela — were created by scientists long ago, and don’t fully align with how different parts of our vision have different sensitivities to different-colored lights, Bullough said. That means that even though a light meter might say a pair of halogen headlights has the same light intensity as a pair of LED headlights, our eyes will see the bluish LED one as brighter because it’s more likely to be picked by our peripheral vision, making our brains prioritize it as important or alarming.

The second factor, Bullough said, is that the intensity of headlights really has increased over the last 10 to 20 years.

“If we think about the........

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