Frequently Asked Questions About Light Pollution

What's the single greatest source of light pollution?

You might think that the biggest causes of light pollution are large commercial facilities like shopping malls and car dealerships. While these can certainly be egregious individual sources that have a serious impact in the neighborhoods surrounding them, overall the greatest contribution to light pollution comes from streetlights. Lighting experts estimate that about a third of all the light beamed uselessly into the sky comes from streetlight fixtures. Even fully shielded streetlights create some skyglow, due to the reflection of their light upward from the ground beneath them. However, most streetlights in use today are not well shielded and beam some of their light directly into the sky. And, of course, they're on all night, every night.

Doesn't having more light make my nighttime surroundings safer?

As society became more nocturnal, our need for nighttime illumination increased. Without question, some of this lighting is needed. However, along the way officials and business owners began to to equate “more light” with “better safety and security” — even though objective proof of such a relationship did not (and does not) exist.

In 1996, at the request of Congress, the National Institute of Justice conducted a landmark assessment of crime and violence in the United States. The study found that little research to support “brighter-is-safer” approaches and even suggested that in some circumstances (such as ATM kiosks) poorly designed lighting can actually increase your vulnerability.

More recently, officials in Chicago experimented with increased nighttime lighting as a deterrent to crime. The result? In the area where lighting was added, crime actually increased significantly — by as much as 20% for certain types.

The bottom line? Night lighting might make you feel safer, but there’s no guarantee — and no proof — that it will actually improve your safety and security.

(other FAQs to come — check back soon!)