I don’t think that you will find such a measure of the effectiveness of CCTVs ready at hand, but I will follow this question to see what materializes.

The effectiveness of CCTV lies mainly in

(1) the deterrent effect they have,

(2) the evidence they provide for post-event investigation and prosecution, and

(3) the immediate alert they can provide during a crime for timely intervention by police.

The threat of investigation and prosecution (2), and the threat of immediate stopping intervention (3) naturally motivate deterrence (1). But post-event investigation and prosecution of course provides no stopping force other than deterrence during the moments of a crime. If the CCTVs are not supervised attentively at all times, moreover, then stopping intervention (3) becomes very unlikely. It is a matter more of chance than of design in security measures.

So the main effectiveness of CCTV for immediate, timely protective security is deterrence (1). And a measure of CCTV effectiveness has to include a measure of deterrent effect. This is obviously problematic.

There has been some work on quantitative measures of deterrence in connection with deterrence through “target shifting”, when protective measures at one site bias criminals toward other sites, demonstrating a significant “force multiplier” effect of deterrence (1) when timely intervention (3) is the foremost justification for surveillance at high-security events, but this may not apply to CCTV generally, when crimes are impulsive, opportunistic, and carried out with little prior planning, and when attentive supervision of CCTV is rare.

It appears, moreover, that you ultimately want a measure of the comfort that comes to the general public from the effectiveness they subjectively attribute to each of the three mechanisms above. This subjective appreciation by the general public may of course differ significantly from the “true” effectiveness that would be more objectively be attributed to each of the three mechanisms by an analysis of the statistics of criminal inclinations and behaviour, with and without CCTV. Thus an objective measure of CCTV effectiveness may not actually serve your purpose.

Subdividing effectiveness into its three different modes acting simultaneously, and drawing a clear distinction between subjective and objective measures of effectiveness for each mode, may help progress toward an answer.

Dear Roland,

Thanks for your valuable contribution. Three aspects of CCTV effectiveness you mentioned do really capture the concept that I am thinking to study. Thanks again.

Dear Sedat,

You might know these studies published in the Campbell Collaboration, which might help your preparation:

http://campbellcollaboration.org/lib/project/49/

http://www.campbellcollaboration.org/lib/project/199/

good luck

olivier

Thanks Olivier

Olivier's first reference was very interesting (and covers most of Ronald's comments nicely).

Coming from an experimental background, these sorts of studies bother me, since they tend to be fairly circumstantial.  I suggest it would also be valuable to try addressing some other angles:

• you mention public fear of crime - I'm sure we're all aware of the paradox that crime is generally decreasing, but public fear is if anything, heightened.  I suspect that overt signs of enforcement (such as even dummy CCTV, but also including patrols, lighting, etc) may create a sort of placebo effect.  But that CCTV provides more and "scarier" pictures to frighten people (disproportionately).
• it might be interesting to measure public perception of how much area is covered by CCTV, how often they are broken, how/whether they are monitored, how long data is retained.  Even the effective resolution of cameras, given how crime fiction on TV always seem to feature magical levels of "image enhancement".  I would be fascinating to learn how/whether the public is aware of increasing sensor resolution, progress in facial recognition software, and the feasibility of storing all recordings (forever).
• it's also true that surveillance influences individuals differently: some kinds of people may find it comforting, others quite aversive.  Certainly it will provide skewed biases on behavior for individuals who hold different attitudes.  I wonder whether the conspicuousness of cameras could be treated as a factor to get at this (invisible cameras, cameras with "active" indicators, PTZ cameras with tracking vs scanning).

Dear Mark,

Your sugesstion regarding the measurement of public perception of how often CCTV cameras are broken, the duration of data storage. and the area covered by the CCTV is really interesting point.

Thanks

Hello Sedat,

There are several ways for evaluating the performance of CCTV cameras, as deduced from the interesting previous messages. For this reason, in my own experience, it is good for you to use all the possible metrics if you want to robustly evaluate your approach. In my case, I have worked in automated video-surveillance of suspicious behaviors in shopping malls and I used metrics specially focused on tracking. You can see a more detailed description of evaluation techniques in our last publication in this topic:

http://www.sciencedirect.com/science/article/pii/S0957417415004182

In the following video, you can better understand the proposal:

https://www.youtube.com/watch?v=Rqk-vFKzAcQ

Good luck with your research!

For more information about our research, please visit my Webpage:

http://www.robesafe.com/personal/roberto.arroyo/

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