Closed circuit television (CCTV) surveillance cameras serve many functions and are used in both public and private settings. CCTV is viewed as a technique of “formal surveillance” and as such it might enhance or take the place of security personnel. Cameras can be used to aid crime prevention, the detection of offenders, and crowd control or public order scenarios. The focus of this overview is on the prevention of personal and property crime.
This narrative is primarily based on one systematic review covering 41 studies. A second review provided additional evidence in relation to the mechanisms and moderator sections below.
Overall, the evidence suggests that CCTV can reduce crime. There are however, some important considerations as discussed below.
In looking at crime type specifically, the most significant reductions were in vehicle crime and property crime and there was no evidence of an effect on violent crime.
Review 1 estimated that overall, for every 100 crimes, an average of 16 crimes were prevented with CCTV (based on 41 studies) and specifically for vehicle crime, for every 100 crimes, an average of 26 crimes were prevented (based on 22 studies). There was no evidence of a backfire effect (where crime increases) across the evaluations reviewed.
This evidence is taken from a systematic review covering 41 studies, which demonstrated a high quality design in terms of having a transparent and well-designed search strategy, featuring a valid statistical analysis, sufficiently assessing the risk of bias in the analysis and considering the validity of the way outcomes are measured and/or combined. The review did not quantify an overall effect for unanticipated outcomes such as displacement caused by the intervention or conduct a separate analysis for distinct evaluation research designs.
In both reviews 1 and 2 the authors note that CCTV might reduce crime by: a) deterring criminals by increasing their perception of the risk of getting caught; b) increasing the actual risk of getting caught; c) encouraging the public use of an area thus affecting the criminals’ perceptions of risk (by increasing informal surveillance by the public); d) encouraging potential victims to take additional precautions; e) signalling improvements in the area to the public which encourages community pride; f) supporting the effective deployment of security staff to incidents more effectively.
Review 2 notes that possible increases in crime could occur if; a) the police became overly reliant on the cameras and reduced their own vigilance, or b) due to the presence of cameras fewer people used the area, which reduced levels of natural surveillance.
However, none of these potential mechanisms are empirically tested and the authors note that this should be done. Review 2 reported that CCTV did not encourage or discourage use of the area, which suggested no change in natural surveillance.
There is good evidence that CCTV effectiveness varies considerably by context.
In the reviewed studies (review 1), for every 100 crimes:
An average of 51 crimes were prevented within a car park context (based on 6 studies).
An average of 19 crimes were prevented within a UK-based context (based on 34 studies).
An average of 19 crimes were prevented within a UK-based context (based on 34 studies).
The effect of the following were non-significant; city and town centres (20 studies); public housing (8 studies); public transport (4 studies); non-UK studies (7 studies). CCTV, therefore, appears most effective in a car park setting, and appears to be more effective in the UK than the other locations tested (largely the USA). Further evidence (review 2) suggests that CCTV can also be effective in the outskirts (suburbs) of a city (preventing 31 crimes for every 100).
The reviews (1 and 2) note that the types of camera tested in the studies varied (e.g. pan, tilt, zoom cameras). The technical specification of cameras (e.g. their positioning or ability record at night) should be considered during implementation. Most of the successful CCTV systems involved active monitoring of live footage from the cameras, typically by security personnel (i.e. not the police). The effective operation of the control room is therefore an important factor. Success also appears to be related to stronger public support, less political resistance and better funding. Public support can vary by context - for example, cameras attract more support in car parks. Implementation should be based on a careful analysis of the local crime problem - projects should have clear objectives and project managers with relevant knowledge should communicate with police.
Review 2 reported on the degree of coverage of the cameras. Overall, the effectiveness of a scheme was correlated (r= 0.63, p=0.021) with how much of an area the cameras covered. This suggests that having a high degree of coverage of the cameras is an important factor in gaining successful outcomes.
CCTV also appeared more successful when combined with other interventions (improved lighting, fencing, better parking payment schemes, security personnel, youth inclusion). For example, in review 2, the authors looked at the impact of the implementation of CCTV where other schemes were operating. The schemes that showed the largest desirable effects of CCTV on crime also included improvements in lighting.
There is no information on costs of CCTV in either review but the authors of review 1 highlight some sources of data regarding the costs of implementation: a) One study estimated that more than £250 million (approximately $500 million) of public money was spent on CCTV over the 10-year period of 1992 to 2002 in the UK; b) according to another report, between 1999 and 2001 alone the British government made available £170 million (approximately $340 million) for “CCTV schemes in town and city centres, car parks, crime hot-spots and residential areas”; c) Estimates from the USA, suggest that figures range from $25 million spent on cameras in buses and subway stations in New York City, to $5 million spent in Chicago on a 2,000- camera system throughout the city centre, to more than $10 million spent in Baltimore.
The reviews also note that re-deployable CCTV cameras - that can be moved easily between different locations – might be a less costly option. Information on the monetary costs or benefits of intervention are not discussed.
The authors note that the evaluations included in their reviews varied in important ways including the duration of the follow-up periods (e.g. those in the UK tended to have longer follow-up).
Not all crime is reported to the police. Thus, CCTV cameras may identify crimes that would otherwise go unreported. Review 2 reported an increase in crime reporting rates in some intervention areas.
Implementers should consider possible threats to privacy and civil liberties.
Displacement of crime or diffusion of benefits to neighbouring areas are possibilities and should be considered.
Cost information for CCTV is difficult to determine – as technologies change costs can increase or decrease, and costs will vary by location and the characteristics of the cameras.
This overview does not address the effectiveness of CCTV as an aid in the detection of crime, deployment of resources or control of public order, which in certain cases can be significant.
This review has highlighted some gaps in the research base – specifically more is needed to directly test the mechanisms underlying CCTV – i.e.
how does it work.
There is evidence that CCTV modestly reduces crime overall. There is also strong evidence that it is particularly effective in reducing crime in car parks. In looking at crime type specifically, the most significant reductions were for vehicle crime and there was no evidence of an effect on violent crime. Implementing CCTV with wider coverage, and in combination with other interventions, such as street lighting, can increase effectiveness. This overview does not consider the effect of CCTV on detection, public order or other uses.
Welsh, Brandon C. and Farrington, David P. (2009) 'Public Area CCTV and Crime Prevention: An Updated Systematic Review and Meta-Analysis', Justice Quarterly, 26: 4, 716 — 745
Farrington David P, Gill Martin, Waples, Sam J and Argomaniz, Javier (2007) The effects of closed-circuit television on crime: Meta-analysis of an English national quasi multi-site evaluation. Journal of Experimental Criminology, 3, 21-38
This narrative was prepared by UCL Jill Dando Institute and was co-funded by the College of Policing and the Economic and Social Research Council (ESRC). ESRC Grant title: 'University Consortium for Evidence-Based Crime Reduction'. Grant Ref: ES/L007223/1.
Uploaded on 19/02/15