Measuring Potential Diffusion of Benefits and Crime Displacement Near Public Surveillance Systems

• NCJ Number: 242240
• Author(s): Samantha S. Lowry, Nancy G. La Vigne
• Date Published: October 2011
• Length: 4 pages
• Agencies: NIJ

Annotation

This article describes The Urban Institute’s evaluation of the use of public surveillance cameras in three cities: Baltimore, Maryland; Chicago, Illinois; and Washington, DC.

Abstract

Results indicate that while cameras had an impact on crime in their intended spheres of influence, no evidence of displacement to nearby areas was detected. In addition, more rigorous analyses also yielded no evidence of a diffusion of benefits to areas beyond the camera viewsheds, contrary to the spatial results. This study specifically focused on how geographic information systems (GIS) and spatial analyses were used to measure potential diffusion and displacement effects in the areas adjacent to the camera locations. Overall, the spatial techniques described in this article provide a picture of the movement of crime in the vicinity of surveillance cameras. Density maps along with mean center techniques depict how the concentrations change and shift in and around the camera areas, and whether hot spots were truly dissolved or if they merely moved to a new location several blocks away. The most scientifically rigorous of methods were and offer persuasive evidence that the crime reduction impact of cameras was not countered by a displacement of crime to other areas. However, the degree to which cameras result in a diffusion of benefits remains an open question, with conflicting findings and the more rigorous test yielding no definitive signs of benefits beyond the camera viewsheds. 2 figures and 2 notes