Research indicates that improving environmental factors in an area may help to reduce crime by increasing natural surveillance, community pride and informal control and making the area less lucrative to potential offenders. However, a primary criticism is that improving the environmental design in one area will only move, or displace, the crime to an adjacent area. There is also some question regarding the possible financial impact of such significant capital investments.
The intervention evaluated in this study involved improving street lighting in two neighborhoods in the United Kingdom and then comparing a number of benchmarks in those neighborhoods to adjacent neighborhoods and control (non-adjacent) neighborhoods. The effects of the intervention on crime count, crime rate, and community fear of crime were evaluated to determine the presence of a reduction in crime and whether crime displacement occurred. Additionally, the original study aimed to provide a cost-benefit analysis. However, the costs of crime for the UK were not available at the time. The follow-up study addressed this issue after these costs were released.
- Will improved street lighting decrease crime after dark in the experimental area?
- Will improved street lighting decrease crime at all times of the day in the experimental area?
- Will crime be displaced to untreated neighborhoods adjacent to the experimental area?
The Dudley neighborhood included before and after measures of crime for an experimental neighborhood and a non-adjacent control neighborhood. The Stoke-on-Trent (Stoke) study had the addition of before and after measurements of adjacent neighborhoods to determine the extent of displacement. Control neighborhoods were chosen based on their similarity to the experimental neighborhood. The displacement neighborhoods were chosen because of similarities and the fact the physical transition between the control and displacement was indistinguishable. Victim surveys were conducted in both neighborhoods and measured the prevalence and incidence of crime for the 12 months prior to and the 12 months after the improved street lighting.
In the follow-up study, the cost-benefit analysis was completed based on crime costs for 1993. Costs did not include the more controversial and intangible “quality of life” costs.
This study was not a randomized study, but did include comparisons between a control neighborhood and the experimental neighborhood. One limitation noted by the researchers is that analysis could not be done to assess the effects of individual properties on the neighborhood as a whole. Follow-up surveys could not be conducted in following years due to additional crime prevention measures, which would have confounded results. The follow-up study notes a few limitations, including the fact that not all of the crime reduction can be attributed to the improved lighting, so the hypothetical savings may be too high.
In Dudley, decreases in both the prevalence of crime and the crime rate were statistically significant and there were no significant changes in the control area. The changes that occurred in the experimental area were significantly different that those in the control area.
In Stokes, there were decreases in both prevalence of crime and crime rate. This decrease was significant across all crimes, except burglary. Additionally, there were decreases in prevalence and crime rate in the adjacent areas, although none reached the level of statistical significance.
The capital costs of the street lighting were greatly outweighed by the benefit. Even if the reductions in crime only lasted one year, the savings from the crimes prevented exceeded the costs by 2.4 to 10 times.
The improved lighting decreased both crime itself and the fear of crime for residents. The researchers believe that the lighting increased community pride, community cohesion, and informal social control, which acted as a deterrent to potential criminals. The cost-benefit analysis of this project also indicates that, used appropriately, it is a cost efficient and practical way to address some crime problems.