Program Goals/Program Components
The city of
Of the 18 cameras, eight were pan, tile, zoom cameras. These cameras can be controlled by a remote operator so that they can tilt up and down, pan around the surrounding area, or zoom in on a particular segment of the viewing area or “viewshed.” These images are viewed in real time by a police officer. Images are recorded digitally and stored for up to 12 days. These cameras provide good-quality images that allow a license plate to be read up to a block from the camera or for street activity to be viewed up to three blocks away. In
The remaining 10 cameras were Portable Overt Digital Surveillance System cameras. They do not allow for real-time image viewing. These cameras are moveable, the recording system is located in a bullet-resistant unit, and the camera emits a flashing strobe light to attract the attention of people in the area. The images can be viewed by patrol officers with equipment designed to access a wireless link. Images can be stored digitally for up to 5 days. The retrieval of images from these cameras can be time-intensive: it requires the help of a city street engineer and can take up to two hours.
The underlying theory for the effectiveness of CCTV is deterrence theory, which predicts reductions in crime resulting from potential offenders’ perceptions of increased risk of detection and capture.
The hierarchical linear modeling (or HLM) analysis of serious crimes found that camera implementation had no significant impact upon the amount of serious crime in the target area. Serious crime decreased slightly after camera implementation (by about five percent), but this drop was not statistically significant. While the average indicated no significant reductions in serious crime, there was considerable variation in outcomes for individual sites. For instance, serious crime was reduced and there was evidence of a diffusion of positive benefits to surrounding streets at four sites. The authors also noted that the base level of serious crimes was very low and perhaps too low to show any significant effect of the cameras.
Camera implementation significantly reduced disorder crime in the target area. After camera implementation, the average expected disorder crime count for the target areas was 16 percent lower, after controlling for all other variables. While the average indicated significant reductions in disorder crime, there was considerable variation in outcomes for individual sites. For instance, four sites experienced no reduction in disorder crime after implementation.
All Crime (Serious and Disorder Combined)
The implementation of cameras significantly reduced the number of crime events within the target areas. The months following the implementation of the cameras saw a statistically significant 13.3 percent reduction in expected crime counts after controlling for the other factors. While the average indicated significant reductions in all crime, there was considerable variation in outcomes for individual sites.
There were mixed results with respect to displacement/diffusion of benefits across evaluation sites.