As in almost every city in the United States, the risk of crime victimization in New York City differs between the economically disadvantaged and the more affluent.  Addressing this disparity while maintaining New York City’s crime reductions is a key policy challenge. One promising approach is to invest in making the physical environment less conducive to criminal activity.  It has long been thought that street lighting can impact crime and yet little rigorous evidence exists to support this contention -- until now.

In partnership with the Mayor’s Office of Criminal Justice, the New York City Police Department and the New York City Housing Authority, Crime Lab designed a randomized controlled trial involving nearly 40 public housing developments, all of which had elevated levels of crime, and half of which received new lights and half did not

The lights study found that the developments that received new lights experienced crime rates that were significantly lower than would have been the case without the new lights. Among other findings, the study concluded that increased levels of lighting led to a 36% reduction in "index crimes" — a subset of serious felony crimes that includes murder, robbery and aggravated assault, as well as certain property crimes — that took place outdoors at night in developments that received new lighting, with an overall 4% percent reduction in index crimes.

These results have implications for New York City and beyond. Unlike many jurisdictions around the country, New York City has shown that it is possible to reduce crime and, at the same time, lower the local jail population. The city’s success in this area is credited in large part to innovations in policing undertaken in recent years by the NYPD. The lights study results demonstrate that not only can environmental design impact crime, but that investments in changes to the physical environment such as new street lights can augment the city’s efforts to promote public safety and help reduce citywide inequalities in crime reduction without having to resort to building new jails or incarcerating more people. And there is evidence that residents appreciated the new resources introduced into communities during the lights project: survey results suggest that fully two-thirds of NYCHA residents felt favorably about the new lights.

While there have been a small number of prior studies of impact of lights on crime, this effort marks the first use of a rigorous, randomized controlled trial (RCT)—the gold-standard in scientific research—to measure the impact of street lighting on crime.

You can read the preliminary technical report here.