The Swedish National Council for Crime Prevention commissioned the report, which contains a systematic review of 76 studies that examine the effects of video surveillance on crime in public spaces. When the results of these studies were pooled using a procedure called meta-analysis, video surveillance was found to reduce crime by on average 13%.

Different effect in different settings
The new report is an updated version of a 2009 review, which found a large deterrent effect of video surveillance in car parks, but not in other public settings. However, the updated review suggests that cameras can be effective in more settings than previously thought, according to Eric L. Piza, one of the authors of the report.

– Whereas the prior review found that effects were confined to car park environments, we found varying levels of evidence for CCTV in residential areas, city/town centres, and ‘other settings’ in addition to car parks, he said in an interview with SecurityWorldMarket.com.

Many of the 76 studies that were included in the review reported effects of video surveillance on multiple types of crime. When calculating the average of these effects, the review found that cameras reduced crime in car parks and residential areas, but no statistically significant changes in city centres or public transport settings.

Could reduce crime in city centres
Since calculating the average effect across all types of crime produces a conservative estimate, the researchers also produced an upper-bound estimate by pooling the largest effects of each study. Using this “largest meta-analysis”-procedure, cameras were estimated to reduce crime by 17% in city centres.

– Public safety agencies need to be mindful that only the largest effect meta-analysis found evidence of crime reduction in city/town centres. This suggests that CCTV will only work in city/town centres when the maximum potential effect is achievable, said Eric L. Piza.

The finding that video surveillance may reduce crime in city centres is also supported by a recent study published in the Journal of Scandinavian Studies In Criminology and Crime Prevention. That study, which synthesised evidence from high-quality studies of CCTV, found that cameras reduced crime by 24-28% in public streets and urban subway stations.

Important to actively monitor cameras
Another finding of the report was that video surveillance tended to reduce property crime, vehicle crime, and drug crime, but not violent crime or disorder.

– Overall, our review found that CCTV did not have a significant effect on violent crime. Therefore, cities suffering from violent crime problems should consider whether resources would be better allocated towards other strategies besides CCTV. For jurisdictions with existing CCTV systems, agencies may need to make changes to their existing strategies to have any chance of reducing violence, said Eric L. Piza.

According to Eric L. Piza, it is particularly important to replace passive CCTV systems with active monitoring.

– Active CCTV monitors, who can detect incidents of concern in real time, may be able to deploy police officers on-scene before a situation escalates into serious violence. Some of the studies included in this review found evidence that active CCTV monitoring provides such benefits. The more completely a city/town centre is covered by cameras, the better CCTV operators can identify and deploy resources to incidents of concern.