Posted by: Karim Vellani | August 4, 2008

Crime reduction effects of public CCTV cameras

Between July 2006 and November 2006 the City of Philadelphia installed 18 CCTV cameras at various locations in the city. Two types of cameras were installed. Phases I and II saw the installation of 10 police monitored cameras at four locations. These cameras are monitored by Philadelphia Police Department (PPD) officers, and have the capacity to pan, tilt and zoom (PTZ). Phase III took place during November 2006 and saw the installation of a total of 8 PODSS cameras at 8 locations in the city. These cameras are not monitored at police headquarters, but officers can monitor video feeds wirelessly from within patrol cars in the vicinity of a camera. Furthermore the PODSS cameras record the street scene continuously on a digital hard drive. If a crime is known or suspected to have been committed within the view of a camera, police officers retrieve the hard drive manually from the camera and review the recording.

The evaluation suggests that while there appears to be a general benefit to the cameras, there were as many sites that showed no benefit of camera presence as there were locations with a noticeable impact on crime. Discussions with police commanders and camera operators may explain the disparity between the various sites. An in depth study of the dynamics of individual camera locations and the arrest patterns at these sites may also explain the findings. These conversations and research will inform a greater understanding of the best locations to place cameras, and potentially help the city get a better cost benefit return on the city’s future investment by deploying forthcoming cameras in locations that provide the best potential crime prevention benefit.

Read the Philadelphia CCTV Study



  1. The Philadelphia study is certainly one of the better and more recent examinations of the effectiveness of CCTV systems. You may be interested in reading my report on over a dozen CCTV studies at



  2. Academic assessment of video surveillance efficiency is generally based on the “bottom line”, in other words, how many crimes have been deterred or displaced as a result of CCTV being present.

    What it normally fails to do, is address the results in relation to the actual deployment of specific technology and techniques, which can make all the difference between a system that is useful, and a system that is efficient.

    Producing an evaluation of what has been done is of course very useful, but then producing a re-modelled conclusion based on predicted results given an alternative and more objective system design, is in my experience never undertaken, and that IMHO is an opportunity missed.

    Longterm, deterrence as a function of CCTV, is only ever going to be sustainable if the effect is based on the concept of “Deterrence through Detection” or DtD. If the systems are seen to work well, then in essence they will prove to work better.

    Until the mechanics and objectives of video surveillance are more widely accepted and understood, the potential for the technologies deployment in tackling a breadth of criminality, will sadly only ever be realised at something barely above a superficial level.


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