John Bullough (Lighting Scientist)

I'm not sure anybody has a dream of becoming a lighting scientist when they're a kid. It actually started out as a summer job at the university where I went to school. And I actually thought it was the Lightning Research Center, which seemed a lot more exciting. I was a little disappointed when I learned it was lighting.

But as I learned more about it, it really became something that was interesting to me about light that's all around us. And it affects not only the way we see, but the way we sleep and a lot about our health and well-being. And it hasn't gotten boring after 30 years.

Well, there's two ways to answer that question. But fortunately for your listeners' sanity, the answer is yes to both of those. The first way has to do with the color of LED 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.

There are LED lights that are a warm white color that would look very similar to halogen lights, and they would be much more comfortable to look at at night. So that's one possibility. Another possibility, and something we probably should pay more attention to, is the aim of our headlights.

Headlight aim is something that some states, but not most, actually require as part of their safety inspections. So drivers could ask their mechanic once a year to have their headlight aim checked and to adjust it if needed.

Yes, the Federal Department of Transportation is very interested in the glare question. They've been getting a lot of complaints from the public

in the last 20 to 30 years about glare specifically and so they have been looking into what might be done certainly what could be done is some upper limits on the overall intensity from low beam headlights that's one possibility maybe some restrictions on the height of headlight heights on vehicles is another possibility so there are some things that could be integrated into regulations to help reduce the glare issue

And the way that we define light, the definition of light, when we measure it, is actually over 100 years old. And it actually discounts a lot of the blue wavelengths, the blue part of the color spectrum. So in that sense, even though the light meter may say two headlights are equal, our eyes will see the LED bluish one as brighter.

The second way to answer that question is to actually use the light meter and measure Intensity of headlights have actually increased over the last 10 or 20 years.

It's actually both kinds of headlights. Both the halogen headlights and the LED headlights have increased in their luminous intensity.

Headlights are getting brighter, they're getting smaller, and they're getting bluer. And all three of those things increase discomfort glare.

If we think about the reason we have headlights, they're not to create glare to other drivers. They're to help us see things along the road so that we can avoid colliding with those. As we've paid more attention to headlights and their ability to provide visibility, It's become clear that they don't always do the best job.

And so headlight intensities have actually been increasing in intensity, in part because of things like the Insurance Institute for Highway Safety's safety ratings that when they first started coming out about 10 years ago, were giving headlights pretty poor grades in terms of their ability to help us see things at night.

Their intensity, the maximum intensity that they produce actually has increased.

That's right. More than 90% of all new cars have LED headlights only. So halogen headlights are going to be going away pretty quickly. And LEDs are much more efficient than halogen headlights. So they use less energy and that corresponds to fewer vehicle emissions and things like that. That's a good thing. But because they're more efficient, LED headlights can actually end up having more light.

And some of that light actually ends up in other drivers eyes or in their rear view mirrors.

We're driving more pickup trucks and SUVs than we were in earlier years. And so headlights have gotten higher off the ground than they used to be.

And all the requirements for headlights are relative to the headlight itself. So that means headlights are pushing more light into the eyes of drivers, especially drivers who are driving passenger cars and sedans. Their eyes are lower to the ground and now they're looking at headlights that are higher mounted off the ground.

Another factor is the fact that low beam headlights are very sensitive to the way that they're aimed. And when you shine your lights on a garage door for example, you see a broad horizontal band of light with a pretty dark area above and a bright area below. That bright area is supposed to be aimed slightly downward so that you're lighting up the road, which is what we want to see.

If those headlights are even mis-aimed just a little bit upward, that bright band of light is now going to be shining into other drivers' eyes. And we found that headlight aim, especially when they're pointed slightly upward, can really increase the amount of glare by a lot.