Study
Piza (2016) conducted a quasi-experimental study using propensity score matching (PSM) to evaluate the effectiveness of police-monitored CCTV cameras in Newark, New Jersey, on deterring crime. Viewsheds were developed, using the same methods as detailed in Study 1 (above), for all CCTV cameras. However, the size of the viewsheds was reduced from 582-foot to 423-foot buffer zones.
Cameras were installed in four phases from March 2008 to April 2010. Comparison viewsheds, placed in hypothetical camera locations, were selected via PSM, using the following variables: 1) the number of crime incidents during the 1-year pre-installation period; 2) number of arrest incidents during the 1-year installation period; 3) sociodemographic variables, including concentration of social disadvantage, racial heterogeneity, residential population, and ambient population (those who frequent the area but do not live there) in the surrounding 2010 U.S. Census block; and, 4) whether the viewshed fell into one of four Newark police precincts.
After the propensity scores were calculated, a matching process was conducted that accounted for the phase in which a camera was installed. The author used a final sample size of 228 (114 treated, 114 untreated) viewsheds for automobile theft, 224 (112 treated, 112 untreated) viewsheds for theft from automobiles, and 226 (113 treated, 113 untreated) viewsheds for the violent crime analysis.
Pretest and posttest data included NPD administrative data for 1 year before (pretest) and after (posttest) installation for automobile theft, theft from automobiles, as well as a composite violent crime variable that included murder, non-fatal shootings, and robbery.
Odds ratios and average treatment effects were calculated to measure the overall change in automobile theft, theft from automobiles, and violent crime in treatment versus comparison viewsheds. Micro-level effects were also calculated to determine whether individual treatment viewsheds experienced a statistically significant treatment effect relative to their matched control units. Subgroup analyses were not conducted.
Study
Caplan and colleagues (2011) used a quasi-experimental design to evaluate the deterrent effect of police-monitored, closed-circuit television (CCTV) cameras on crime in Newark, New Jersey.
The study examined the effects of cameras installed before and after two installation time points (March and July 2008) on measures of crime. Two different placement strategies were applied. The placement of cameras installed in March was dictated by sponsors who paid for the cameras and required that they be placed in Newark’s Business District. The cameras installed in July were placed in known high-crime areas in consultation with Newark Police Department (NPD) personnel. Only dome cameras were examined in this study (n=73); they have the greatest range of motion and their aim is not easily visible to those on the ground.
For the unit of measurement, the authors calibrated the public area visible from the location of the camera, called a viewshed, to view a 582-foot radius (or buffer zone) around the camera. They used Google Earth and ArcGIS to digitize the viewshed area, in addition to tools in the NPD’s CCTV control room, to validate the aerial data with what was occurring in real time.
In addition to the 73 experimental viewsheds, 73 comparison viewsheds were created using two criteria: 1) the area had to be patrolled by the NPD, and 2) NPD administrative data had to be available for the area. Comparison viewsheds were randomly placed in hypothetical camera locations by using the same technical system as the CCTV treatment viewsheds.
NPD administrative data were examined for experimental and comparison viewsheds for the 13 months before (pretest) and 13 months after (posttest) the camera installations. Crime was measured by number of shootings, automobile thefts, and thefts from automobiles that occurred within the areas. T-tests were used to compare the effects of CCTV in the experimental viewsheds relative to the comparison viewsheds.
Two subgroup analyses were conducted. The first compared the deterrent effect of strategically placed cameras versus randomly placed cameras. The second compared the deterrent effect on crime of cameras in low-crime areas, versus cameras in high-crime areas.