Effectiveness of Street Lighting in Preventing Crime in Public Places

In pooling the effects of 17 studies that could be included in the meta-analysis, it was found that street lighting led to a significant 14% decrease in crime in experimental areas compared with comparable control areas. While not every study was effective in preventing crime, desirable effects of street lighting interventions were greater in studies that measured both night and day crimes than in studies that only measured night crimes. This translates to a significant 18% decrease in crime for night/day studies compared to a non significant 3% decrease in crime for night only studies. These findings suggest that a theory of street lighting focusing on its role in increasing community pride and informal social control may be more plausible than a theory focusing on increased surveillance or deterrence.

It was also possible to use meta-analytic techniques to investigate the effects of street lighting interventions on violent and property crimes, the two main types of crimes that were measured in the studies. Street lighting interventions were followed by a significant decrease in property crimes (12%), but not in violent crimes. Importantly, this effect on property crimes closely approximates the overall effect of street lighting interventions on total crime (14%), suggesting that the overall effect on crime may be largely a function of street lighting's impact on proprety crimes. Cost-benefit analyses of improved lighting suggested that the benefits (in terms of fewer crimes) outweighed the costs, but similar analyses of part-night lighting also suggested that this had benefits.

Many of the recommendations that we made 14 years ago (see Farrington and Walsh 2007) for research on the effects of street lighting on crime are still needed today. For example, future evaluation studies should include several experimental areas and several adjacent and comparable non-adjacent control areas. Adjacent areas are needed to investigate crime displacement and diffusion of crime prevention benefits. In addition, a long time series of crimes should be studied to investigate pre-existing crime trends, as well as the extent to which any effects of street lighting interventions persist or wear off over time. It would also be highly desirable for researchers to carry out more cost-benefit analyses of street lighting interventions. This would allow for a number of key policy questions to be addressed, such as: Do the monetary benefits to society from decreased crime rates outweigh the monetary costs of implementing and maintaining street lighting projects? To whom do the monetary benefits (or costs) accrue?

Compared to years past, it would seem that an even stronger case can be made today for street lighting interventions to be part of national and local crime prevention policy. A larger body of high quality evaluation research, implemented in a range of high-crime public places, some evidence of value for money, and the enduring impact on crime, especially property crimes, all point to the policy significance of street lighting interventions.