Why People Have Difficulty Driving at Night

At the same time, our pupils, which regulate how much light enters our eyes, shrink with age, says John Bullough, program director at the Light and Health Research Center at Mount Sinai Hospital’s Icahn School of Medicine in New York City. “The older we are, the smaller our pupils are,” he says. “Even for the same light level, there’s less light getting inside our eyeball.” By the time we hit our 60s, he adds, the backs of our eyes are receiving only one-third the light they did when we were 20. “The world just gets darker, day by day,” he says. “The only reason we don’t notice it is because it’s so gradual.” As we age, we also become less sensitive to changes in contrast and thus less able to distinguish objects — like road signs or pedestrians — from their background.

And the darker it gets, the more challenged our sight becomes, especially when it’s a question of spotting objects along the side of the road. A study by the University of Michigan Transportation Research Institute found that pedestrian fatalities were 22 percent more likely to occur on nights when there was a new — and essentially invisible — moon than on brighter nights with a full moon. Plus, in low-contrast conditions, it’s difficult to estimate how fast objects, such as other cars, are moving, and our reaction times are slowed.

What’s more, by the time we reach our late 50s, nearly 1 in 10 of us will suffer from cataracts — a blurring caused by a buildup of protein on the disclike lenses behind our pupils. By the time we hit our 80s, more than half of us will have cataracts. “Everyone who lives long enough, whether their eyes are healthy or not, will experience cataracts,” Bullough says.​

How to lighten up

The good news is that headlights are, in some cases, getting better at lighting the road ahead of us. A testing initiative by the Insurance Institute for Highway Safety (IIHS) has found that vehicles equipped with top-rated headlights have 19 percent fewer nighttime crashes than do cars with lower-rated lights. As opposed to older headlights, which use a halogen bulb backed by a reflective surface, the best new headlights use LED bulbs with a so-called projector lens, explains Matt Brumbelow, a senior research engineer with the IIHS. “Now you can have a much better beam pattern that gets enough light onto the road,” he says.

But even pricey LED lights don’t always ensure good illumination. “You might have a really expensive headlight system that doesn’t do well,” Brumbelow says. “There are lots of LED bulbs not designed to light up the road — they may be there to make a style statement about the car brand.” If you’re considering a new car and if driving at night is a concern, check out iihs.org, which offers overall safety ratings on vehicles, including for headlights.

Still, having the best headlights is only half the battle. You also need to use them well, especially your high beams. In fact, most of us use our high beams a lot less than we could. Curiously, Bullough points out, “low-beam headlights, initially, weren’t ever really designed to be the main headlights for us to be driving with.” They were called the passing beams, he says. “And then you had the ‘driving beams,’ which were your high-beam headlights.”

Over time, owing perhaps to busier roadways and more streetlights, we’ve defaulted to using our “passing beams” for much of our driving. Even on dark, rural roads without much traffic, some three-quarters of drivers typically use their low beams, according to Bullough. As a result, many drivers are “overdriving their headlights” — driving faster than they would be able to stop based on what their headlights can reveal in front of them.

But while lighting the road ahead is one battle, there’s another issue that confounds and distracts nighttime drivers: the headlights from oncoming cars.

Caught in the Glare

Driving at night, you may find yourself occasionally getting “flashed” by oncoming drivers protesting your use of high beams — even when you’re using low beams.

“It’s relatively easy to put a lot of light on the road,” Brumbelow says. “The issue is that you have to do that without glaring other drivers.” And in the U.S., headlights tend to have a sharp “cutoff” — a sort of line where it’s bright below, dark above, Bullough notes. So when an oncoming car hits a bump, it may look to you as if the driver is flashing the headlights.

Another issue: SUVs now outsell sedans by 2-to-1. “The same headlight bulb could, in theory, be mounted 2 feet off the ground in a sports car or closer to 4 feet above the ground on a large pickup or SUV,” Bullough says, which means that the light it casts could shine 2 feet higher — and potentially right into your eyes.

These two factors are compounded by the way headlights are being made today. The newest headlights don’t generate any more light than the old ones. But they can seem to. “A lot of these LEDs have pretty high bluish content, which we seem to be more sensitive to,” Bullough says.

Glare can be annoying or even blinding, a phenomenon that increases as we age. After suddenly seeing a bright light, what’s called photo-stress recovery time takes longer when you’re older. And the presence of oversize infotainment screens and tricked-out cockpit configurations in newer cars makes the interior of the car brighter — thus confusing the eyes even more.

Fortunately, a solution for both visibility and glare may soon be at hand. “Adaptive driving beam” headlights, already common in other parts of the world, have recently been approved by regulators for use in the U.S. — though it will be some time before they begin to appear on American vehicles. Adaptive headlights feature a camera that helps direct LED bulbs away from oncoming cars, “while your side of the road would still be fully lit by the high beams,” Brumbelow says.

Adaptive lights could give drivers about 165 to 195 extra feet of visibility, which, at 65 mph, translates into a couple of seconds of additional reaction time. This could be a boon for older drivers, Bullough suggests. “It almost brings you back to what you could see with low beams in your 20s.”

Kevin Cooley

How to See Better in the Dark

Driving as little as possible after dark is safety tip number one. But sometimes, especially when the days grow shorter, that simply isn’t an option. To maximize your vision:

1. Use your brights at night in almost all cases, except when there are oncoming cars. Drivers often don’t see as well at night as they think they do, and high beams give them the best chance of reacting fast enough to an unexpected hazard.
2. Don’t economize. When buying a new or used car, look for models with top-rated headlights (go to iihs.org/ratings to find a car’s safety ratings). When given a choice, opt for the best headlights available.
3. If your car is several years old, consider getting your headlights and casings replaced. A 2018 study by AAA found that in at least two popular sedan models, degraded headlights and yellowed headlight casings meant that on low beams, the headlights were emitting just 22 percent of the light that new ones would provide, making night driving more hazardous.
4. Keep your windshield and headlights cleaned, for obvious reasons.
5. Reset the illumination levels of your dashboard lights and any in-car screens to low. Bright light inside makes it harder to see outside.
6. Don’t skip the after-dinner coffee. The National Highway Traffic Safety Administration reports that in 2017, 91,000 police-reported crashes involved drowsy drivers.