Are Dark Alleys Really More Dangerous?

A new study says we can dim our streetlights and save energy without increasing crime.

July 30, 2015

Photo: Giuseppe Milo/Flickr

What if we turned off the streetlights? Would our cities turn into Hobbesian nightmares, lawless urban jungles where honest people are little more than fodder for the shiv-wielding predators crouched behind every trash can? Or would everything be the same—just a little darker?

A new study, released Tuesday in The Journal of Epidemiology and Community Health, asks this important question, because streetlights have big financial and environmental costs. There’s no official national data, but the city- and state-level numbers are staggering. New York State, for example, has 1.4 million municipal streetlights that consume 990 gigawatt-hours of electricity each year. That accounts for 752,000 tons of carbon dioxide equivalents, or the yearly greenhouse gas output of 144,000 passenger cars. The annual electricity bill is well in excess of $60 million. Remember, this is just for one state. I believe we have 50 of them.

Streetlights are also major contributors to light pollution. Illuminating the night sky interrupts the natural behaviors of migratory birds, insects, and bats. It inhibits foraging by rodents, who are naturally inclined to stay hidden on brightly lit nights. City lights also discourage the nesting and disorient the hatchlings of sea turtles, most of which are already endangered.

Environmentalists have long pushed for lighting reductions, but usually in the form of efficiency measures. The City of Los Angeles is spending $57 million to convert 215,000 streetlights to efficient light-emitting diodes, or LEDs. The effort has already cut energy consumption from 190 million kilowatt-hours to 110 kilowatt-hours annually, with bigger savings still to come. Between energy savings and reduced maintenance, the city will save more than $11 million annually.

Concerns about safety and crime have prevented the more drastic step of turning off the lights, but this week’s study says it’s at least worth trying. The authors surveyed dozens of cities and towns in England and Wales with reduced lighting on their streets. The approaches varied. Some areas simply switched to LEDs. Many randomly turned off a portion of their lights at different times of the night. Others used the same number of streetlamps but dimmed them significantly. The most aggressive places removed many of their streetlights.

The results are intriguing. Over a three-year period, there was no evidence that crimes likely to be committed in darkness—like burglary, auto theft, robbery, and sexual assault—increased in the areas with reduced lighting.

The authors caution that the results represent a snapshot of just one part of the world. “This is very encouraging,” notes study coauthor Shane Johnson of University College London, “but it is important to note that it does not mean this will be the case under all conditions, and so changes to lighting should be managed carefully."

There are two other big caveats. First, there have been dozens of similar studies on the effects of reduced lighting on urban crime, and the results are wildly inconsistent. Cambridge criminologist Kate Painter conducted a series of experiments in the 1990s that suggested improved lighting significantly reduced crime in urban settings. But a 2006 study, also conducted in the United Kingdom concluded that streetlights have at best a marginal effect on crime rates. A 2008 systematic review—a study that synthesizes existing research—was basically inconclusive. It’s unlikely that this new study will put an end to the argument, either. This is just one more contribution to the literature.

The other issue is perception. Even if streetlights have no effect on crime, they make people feel safe. In a 2013 survey of more than 15,000 people, 93 percent of respondents said they feel safe or fairly safe in well-lit areas, while only 22 percent experienced that warm feeling of security in poorly lit neighborhoods. The authors of this week’s study published some letters to the editor from frightened citizens in the dimmed cities. One writer complained, “Never have I felt so frightened to walk back to my house from the road after a night out.”

Even this point, though, is up for debate. Some researchers claim that the idea of streetlights is what makes people feel safe. In towns that have undertaken lighting-reduction programs, polling data often suggests that the public doesn’t really notice the difference. If this is all about perception, then we would have to think carefully about how to balance the abstract feeling of safety with the real negative effects that streetlights have on the environment and government budgets. Preventing the emission of millions of tons of carbon into the atmosphere may justify some jangled nerves.

This debate will, and should, continue, as research sheds more light on the issue. (Couldn’t help myself.)


onEarth provides reporting and analysis about environmental science, policy, and culture. All opinions expressed are those of the authors and do not necessarily reflect the policies or positions of NRDC. Learn more or follow us on Facebook and Twitter.

Join Us

When you sign up you'll become a member of NRDC's Activist Network. We will keep you informed with the latest alerts and progress reports.