In a recent Sky and Telescope.com article, they review some of the important reasons why overly-bright outdoor night-time lighting can actually contribute to increased crime rates rather than deter crime, as many believe. Developed as a way to make people think they are safer, most street-side outdoor lighting designs today tend toward glaring to create the illusion of crime deterrence. The irony is that these designs can do the opposite of what they’re created to do: make it easier for criminals to take action.
Apparently, these findings were backed up by a study done by the National Institute of Justice in 1996 which assessed crime and violence in the US. The study was called “What Works, What Doesn’t, What’s Promising,” and concluded that indeed, brighter doesn’t equal safer.
There are several reasons for this effect, but one of the most important is the effect glare has on the human eye. As the article points out, really bright lights actually produce conditions that reduce the “discerning power of the eye.” The glare makes it impossible for eyes to function properly.
Unnecessary brightness at night will force the eye to adapt to artificial levels of light. This glare can cause one of two conditions in humans: discomfort glare, which means the light is somewhat uncomfortable, but doesn’t compromise sight, and disability glare, which has a significant impact on the ability of a person to see. As is the case when you encounter high-beam headlights on an oncoming vehicle, disability glare renders your temporarily sightless, making it impossible to know what lies beyond the sphere of light. This creates ideal conditions for criminal behavior.
But disability glare isn’t the only problem with too-bright streets when it comes to crime. The extreme contrast that is created by super bright lights in dark spaces creates perfect pockets in which criminals hide, lying in wait until they feel it is the right time to strike. Whether they’re looking to mug you during your ATM visit or to break into your home after you leave, this contrast creates dangerous conditions.
Thankfully, organizations like Illuminating Engineering Society of North America are looking into the role glare plays in visual performance with the aim of setting standards and making recommendations for lighting designers and the lighting industry as a whole. There is a growing movement to make dark-sky lighting the norm nationwide.