|In December 1993 The Scottish Office commissioned research to evaluate the effectiveness of Closed Circuit Television (CCTV) in combating crime and the fear of crime in city and town centres in Scotland. Two sites were chosen for the study: Airdrie, where twelve open street CCTV cameras had begun operating in November 1992; and Glasgow city centre where a CCTV scheme was due to start in May 1994. Hitherto there had been little independent comprehensive research in Britain (and none in Scotland) on the effectiveness of CCTV in preventing crimes. Similarly, while the concept of crime 'displacement' has long been established, there had been no systematic attempt to measure or account for this effect in previous evaluations of CCTV. This Paper reports the main findings from the Airdrie evaluation. The full evaluation report from the Airdrie study will be published in January 1996. A further and more detailed report evaluating the Glasgow city centre CCTV scheme will be available by Autumn 1997.|
- 21% fewer crimes and offences were recorded in the 24 months after installation of CCTV in Airdrie town centre compared to the 24 months prior to the introduction of CCTV. (This figure, and those given below, have been adjusted to remove the effects of seasonality and underlying trends).
- Crimes of dishonesty, which include housebreaking, shoplifting and theft of and from motor vehicles, saw the largest percentage reduction of 48% in the 24 months after CCTV.
- Crimes of fireraising and vandalism fell by 19% following the installation of CCTV.
- The police cleared up 16% more crimes and offences in the 24 months after CCTV.
- There was no evidence that crimes were 'displaced' from the town centre to areas without CCTV - either the immediately surrounding area or the rest of the Police Sub-division.
|Closed Circuit Television (CCTV) cameras are being used increasingly as a crime prevention measure in public sites throughout the U.K. There is, however, little reliable evidence that they are effective in reducing crime. While evaluations have been carried out on the use of CCTV in open street surveillance, the results have been inconclusive and often contradictory.|
|In December 1993 The Scottish Office commissioned research to evaluate the effectiveness of CCTV in town and city centres in Scotland. Two CCTV schemes were chosen for evaluation; the first of these was located in Airdrie town centre and the second was planned for Glasgow city centre. The Airdrie CCTV scheme - the first open street CCTV project in Scotland - had been in operation since November 1992. a The Glasgow city centre scheme began operating in November 1994.|
- The objectives of the Airdrie evaluation were to assess:-
- the impact of CCTV on crime rates in the areas covered by the cameras;
- the impact of CCTV on the detection of offenders and;
- the extent to which crime might be displaced from the CCTV area, and the nature of that displacement.
|In addition to these objectives, the Glasgow study will assess:- |
- public awareness of, and views on, CCTV;
- the impact of CCTV on the fear of crime;
- the impact of CCTV on the turnover of local retail businesses;
- the installation and running costs of CCTV;
- the impact of CCTV on police operations and manpower.
|Evaluation of CCTV|
|Typically, evaluations of CCTV schemes are based on a comparison of recorded crime figures over a period before and after the installation of the CCTV cameras. However, it is accepted that levels of recorded crime can vary over time for many reasons and it is thus difficult to be certain that apparent reductions in crime are the result of the initiative under investigation.|
|Seasonal effects and underlying trends|
|Often the periods monitored are of insufficient length to allow long term effects, underlying trends or seasonal variation to be accounted for. It is impossible, therefore, to be confident that raw crime figures give an accurate measurement of the effectiveness of the initiative in reducing the level of crime.|
|A common criticism of crime prevention measures, including CCTV, surrounds the potential 'displacement' effect. Crimes apparently 'prevented' may in fact have simply shifted to another place (geographical displacement) or time (temporal displacement). Alternatively, the criminal may choose different methods of committing the same crime (tactical displacement), select a different target (target displacement), or commit a different type of crime (functional displacement). The most commonly identified type of displacement is, however, geographical displacement, where the 'prevented' crime , is committed elsewhere. The main problem in measuring this form of displacement lies in identifying the area to which the 'prevented' crime might have been displaced.|
|While several studies evaluating the effectiveness of CCTV have raised the issue of geographical crime displacement, none to date have been able to show conclusively what, if any, effect displacement has had on the initiative under evaluation.|
|Conversely, it is also possible that the presence of CCTV in one area could have a positive effect in adjacent or nearby areas. This effect has been termed 'diffusion' and exists where the benefits of a crime prevention initiative appear to transcend the area in which the initiative is targeted.|
|CCTV in Airdrie|
|Both the Airdrie and Glasgow studies have been designed from the outset to address the problems of extraneous influences on crime and offence figures and to consider the issue of crime displacement. A total of four years of recorded crime figures (2 years before and 2 years after installation of CCTV) have been analysed for the area covered by CCTV and for 5 areas of increasing geographic size. These were: |
- remainder of the police beats with, but not covered by, CCTV i.e not in camera vision;
- remainder of the police Sub-division;
- remainder of Strathclyde Police N Division;
- remainder of Strathclyde Police area;
- rest of Scotland; that is, excluding the above areas.
|From these areas the remainder of Strathclyde Police 'N' Division was chosen as the most appropriate control area. It was felt that this area, which is made up of the rest of the 6 police beats with some streets in camera vision, the rest of the 'NB' Sub-division, and the remainder of 'N' Division, had more in common with the Airdrie CCTV area than the other areas for which crime data was collected.|
|Adjusted crime and offence figures|
|Average figures were calculated for each crime and offence group and for total crimes and offences for each of the two year before and after periods. These figures were then 'smoothed' to eradicate the effects of seasonal variation and, finally, crime and offence data from the control area (rest of 'N' Division) were used to eliminate the effects of underlying crime trends.|
|Analysis using unadjusted data shows that total recorded crimes and offences in the CCTV area fell by 35% in the 24 months after CCTV cameras became operational. Fully adjusted for seasonal effects and underlying trends, this figure becomes a 21% fall in total recorded crimes and offences. The largest crime groups, in terms of numbers of crimes committed, are group 3 (crimes of dishonesty), and group 4 (fire-raising and vandalism). The post CCTV changes in these crime groups are illustrated in Figure 1.|
|This graph illustrates the 21% decline in total recorded crimes and offences in the 2 year period following CCTV. Crimes involving dishonesty declined by 48% over the same period while crimes of vandalism and fire-raising fell by 19%.|
|Figure 1 |
Percentage changes 2 years after CCTV
(Pre-CCTV = 100)
|Control area - comparisons|
|In order to compare levels of crimes and offences in the CCTV area with those in the control area, unadjusted crime and offence data were used. Figure 2 shows the changes, in percentage terms, in the CCTV area and the control area (rest of 'N' Division), together with the changes for the Strathclyde police area and Scotland as a whole in the 24 months after CCTV.|
|As noted above, total crimes and offences in the CCTV area fell, in raw data terms, by 35% to 65% of their level prior to CCTV. By comparison, total crimes and offences in the control area, which comprised the rest of 'N' Division, fell by only 12% compared to pre-CCTV levels. Crime and offence levels also declined in the remainder of the Force area (to 93%), while for Scotland as a whole, total crimes and offences increased to 102% over the same period.|
|Figure 2 |
Percentage changes 2 years after CCTV
(Pre-CCTV = 100)
|This suggests that while there was a general downward trend in crimes and offences in some areas over the 4 years for which data was collected, the fall in the CCTV area was significantly greater than that for adjacent or nearby areas.|
|Crimes and offences cleared-up|
|A crime or offence is regarded as 'cleared-up' if one or more offenders is apprehended, cited, warned or traced for it. In the 2 years following CCTV the police cleared-up 16% more crimes and offences in the CCTV area compared to the 2 years prior to installation. Improvements in clear-ups were most evident in relation to crimes involving vandalism and drugs and to offences such as petty assault, breach of the peace and drunkenness.|
|Displacement to adjacent areas|
|Attempts were made to find the 'missing' crimes and offences by analysing crime figures and crime patterns in adjacent areas, comprising the remainder of the police beats not covered by CCTV and the rest of the Police Sub-division. Both of these areas recorded slight increases in total crimes and offences in the 2 years following the installation of CCTV. This increase is almost entirely accounted for by the growth in crimes relating to the possession or supply of drugs and to offences committed whilst on bail. Displacement would be suggested if these crimes declined in the CCTV area. However this was not the case; rather, these crimes increased to a similar extent in the CCTV area.|
|Assessing the success of crime prevention measures is always problematic because, in effect, what is being attempted is to measure the extent to which certain events did not happen and to attribute causal explanations to those "non-events". Whilst it is possible to measure changes in the incidence of crime within the target area and to hypothesise a connection between these changes and the CCTV initiative , it is not possible to state with absolute certainty that the latter is entirely, or even partially, responsible for the former.|
|However, confidence in the accuracy of the research findings will be influenced by the time period over which the crime figures are examined and by the number of potentially influencing factors taken into account. Even then, the issue of displacement must be addressed before it is possible to be reasonably confident of the success of the initiative under scrutiny. Examination of crime and offence data for immediately adjacent and nearby areas, while not sufficient to eliminate entirely the possibility of displacement, can provide a strong indicator in this respect.|
|Few, if any, CCTV initiatives have been assessed as comprehensively as the Airdrie Scheme. Four years of crime figures spanning the installation of CCTV and adjusted to take account of external influences indicate a sharp fall in the level of crimes and offences in the CCTV area together with an increase in the number of crimes cleared-up. Neither the reduction in crimes and offences nor the improvement in clear-up rates are mirrored to the same extent in the other areas examined by the study. The possibility that the 'missing' crimes and offences were simply displaced to other areas or types of crime has been examined as thoroughly as possible and no evidence of displacement has been found.|
|It can be stated with some confidence, therefore, that the presence of CCTV cameras in Airdrie town centre has led to a real reduction in the level of crime and to an improvement in the detection of crime. Statistical evidence also reinforces the finding that this reduction has not been exported to immediately adjacent or nearby areas.|
|Further free copies of this Research Findings, or information about the Central Research Unit Programme, can be obtained by contacting the: |
Central Research Unit
The Scottish Office
St Andrew's House
Edinburgh EH1 3DG
The report can also be ordered online from:www.thestationeryoffice.co.uk