A look at causes of glaring headlights

ALBANY — It’s a common theme in the Getting There inbox — why do headlights seem so blinding these days? Have they been getting brighter? Or is it a matter of perception?

There are three parts to the answer, according to John Bullough of Mount Sinai’s Light and Health Research Center; Bullough previously worked at Rensselaer Polytechnic Institute’s Lighting Research Center.

The standards for headlight brightness haven’t changed much since the 1980s, he said.

“It’s partly a change in the technology, it’s partly, I believe, a change in our vehicles, and I think it’s partly a change in the way that we maintain headlights on our cars,” Bullough said.

First, LED headlights have become more common. LEDS are more efficient than halogens but emit a more white/ blue light, while halogens look more yellow. The difference in color makes an LED headlight seem brighter than a halogen with the same light output.

“Now that you’re starting to see some of these whiter or more bluish-white, both streetlights and headlights, they just look a lot brighter, but then someone with a light meter will come and say, ‘No this is the exact same thing,’” Bullough said.

Second, more people are driving SUVS and pickup trucks. Because those types of vehicles are taller, their headlights are more likely to shine into the eyes of drivers in cars lower to the ground. Headlight standards are the same for sedans and wagons as for SUVS and pickup trucks.

Truck SUVS (SUVS that have four-wheel drive or weigh more than 6,000 pounds) were 45 percent of the market in model year 2021, car SUVS were another 11 percent and pickups 16 percent, according to the Environmental Protection Agency’s 2022 Automotive Trends Report.

Sedans and wagons fell to just 26 percent of the market in 2021, a little more than half of their 50 percent share in 2013 and well below their 80 percent share in 1975.

But most importantly, many headlights are simply mis-aimed, pointing up into drivers’ eyes (or lower, at the ground) instead of straight out at the road, Bullough said.

In a 2010 study of vertical aim, Bullough and others at RPI’S Lighting Research Center found that, of 100 in-use vehicles, 60 percent had at least one headlight mis-aimed. The study also included a sample of 20 new cars, of which 45 percent had at least one headlight that was outside the tolerances set by the Society of Automotive Engineers.

“Less than a degree can make a huge difference in creating a lot of glare for an oncoming driver,” Bullough said.

Those findings were consistent with previous studies on mis-aimed headlights.

A few states require that headlight aim be checked as part of inspections, but New York is not one of them.

A solution to headlight glare is in the works, however. Last February, the National Highway Traffic Safety Administration authorized adaptive driving beam headlights, which shine more light on unoccupied areas of the road and less light on occupied areas, like at oncoming cars or drivers in front of you.

They use cameras to detect headlights and taillights and dim the light only in those areas of the road.

Adaptive driving beam headlights are not on U.S. roads yet — manufacturers must complete a battery of tests to prove the headlights work as intended — but have been used in Europe for around 10 years, Bullough said.