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Boyce and Rea (1990) [13] used low-pressure sodium lamps and high-pressure sodium lamps with street lighting and floodlighting distributions along with rural moonless darkness in an experiment where alerted `guards' had to detect and recognise `intruders' walking along a path or moving so as not to be seen in a large open area. Lighting was mostly better than darkness for detection and recognition, but there was little difference between floodlighting and darkness in the open area task. There was no disadvantage for low-pressure sodium lamps in detection or in face recognition, but a (reasonable) caution not based on the results at hand was given against its use when colour recognition could be important. Recognition was better with the more diffuse light distribution (street lighting). Vertical plane illuminances of between 4 and 10 lux were recommended for security lighting installations to give a high level of detection and recognition. The desirability of limiting light spill was not mentioned.
This experiment gave the greatest possible advantage to the guards and the greatest possible disadvantage to the intruders. For instance, the guards had the lights above and behind them, while the intruders had to move towards these intense glare sources. Reversed lighting direction relative to the intruder and guard positions must also occur in practice but it was not mentioned let alone subject to investigation. Nor is this the only practical case in which lighting will tend to aid intruders more than it hampers them. Most security-lit areas are not under continuous surveillance by guards, and prospective intruders may be able to time their incursions appropriately, in which case the lighting may then be a distinct advantage.
The recommended illuminances are doubtless accepted by the security lighting industry as impeccable scientific guidance. Regardless, far brighter installations are commonplace in many developed countries. Presumably, more is considered better, with the excess dependent on how much extra the client can be induced to pay for.
The situation is changing somewhat with the increasing use of sensor-operated lighting and CCTV systems. Nevertheless, security lighting remains in widespread use, signalling the presence of valuable items and ready to assist lawbreakers when there are no police or security personnel close by.
Closed circuit television (CCTV) has been included in this document partly because it is often in competition with street and other public lighting for government crime-prevention funding. For 1996 through 1998, more than three quarters of spending by the UK Home Office on crime prevention was for CCTV systems (Welsh and Farrington 2002, p 44 [116]). Another reason is that it also has its own lighting requirements.
The last decade of the twentieth century saw a rapid rise in the deployment of video surveillance, despite concerns about civil liberty and increasing imaging capability (Honess and Charman 1992 [45]). Existing cameras need artificial light to operate properly at night. Vermeulen (1992) [114] showed that a charge-coupled-device (ccd) video camera with a typical good quality objective lens required a scene illuminance of 26 lux for excellent picture quality.24The required values depend on the type of lamp in use.
Video cameras and high-pressure sodium lights were installed at metropolitan railway stations in Melbourne about a decade ago (Carr and Spring 1993 [18]). The luminaires used are fully shielded (ie, confining the directly emitted light to the horizontal direction and below), but generally both the direct glare from the lights and the lit surfaces of the station tend to be unpleasantly bright by comparison with illumination in most of the surrounding area. Adjacent car parks for rail travellers are also overlit with semi cutoff high-pressure sodium lamps, which are much worse as sources of glare.
A photometric survey25of two of the stations and one of the adjacent car parks indicated that the horizontal illuminance in the carpark and bus shelter ranged from 25 lux to 71 lux. On station ramps and platforms, the range was 88 lux to 452 lux, with a typical value of about 300 lux, over ten times brighter than Vermeulen found to be sufficient for use with CCTV, and also over ten times brighter than is required to reduce fear of crime to near daylight values (Boyce et al. 2000 [14]).
The glare and steep illumination gradients cause visibility losses in the vicinity, particularly for elderly persons and others with increased intraocular light scatter. It would appear difficult to separate overbright lighting and presence of the cameras in any attempts to assess effects on crime and fear of crime.
For video camera installations in general, attempts at cost cutting might increase the need for bright lighting because brighter scenes allow the video camera lenses to be operated with smaller aperture stops (numerically larger f-numbers). This allows the use of cheaper lenses as prime cost items, but imposes greater prime costs for light fittings and greater operating costs for electricity. The desire for sharp images over a greater range of distance could also lead to demands for brighter lighting because smaller aperture stops give increased depth of focus at the cost of dimmer images.
Note that for a given amount of illumination from a high-pressure sodium (HPS) lamp, about 25 % more light is required from a low-pressure sodium (LPS) lamp for the same picture quality (Vermeulen 1992 [114]). HPS is more effective because it is richer in red and near-infrared radiation for which the ccd image sensors are relatively much more sensitive than the eye is.
The literature on CCTV surveillance is extensive. The technical literature on the optics, electronics and displays is fine for engineers. The literature on the use of CCTV for crime deterrence and detection sometimes gives the impression that even basic concepts of the technology are not well understood. Unfortunately this often appears to impact on the value of reports on the effectiveness of CCTV. This section is a review of papers that were readily available and appeared to have something of possible relevance to the main subject of this document.
Closed circuit television (CCTV) appeared to have an initial beneficial effect in reducing car theft in car parks but the evidence for sustained effects was equivocal (Tilley 1993 [108]). Brown (1995) [15] was more optimistic, although this judgement was qualified by evidence that crime was merely displaced to areas out of camera range. Sherman et al. (1997, Chapters 7 and 10) [102] concluded that CCTV was of limited value. In the Bexley (UK) crime study, it was not possible to demonstrate any statistically reliable deterrent effect of CCTV. The authors were only able to say that CCTV was thought to have some value for providing prosecution evidence (Pascoe and Harrington-Lynn 1998 [88]).
Painter and Tilley (1999) [87] is a collection of articles on issues including CCTV and lighting. It includes a version of the review by Pease (1999) [90].
In an attempt to counter an image of Glasgow as a dangerous high-crime area, 32 CCTV cameras were installed in city centre streets in 1994 (Ditton 1999 [27]). No significant reductions in crime resulted in the following year, nor was there any reliable change in the crime clear-up rate. Most incidents occurred between midnight and 4 am and the least between 6 and 10 am. Subsequent viewing of tapes did assist the police in clearing up some serious crimes. Only 41 % of persons questioned in the city were aware of the cameras 15 months after installation. The presence of the cameras had limited impact on public concern.
Twelve video cameras installed 2 years earlier in the nearby town of Airdrie produced somewhat different results. Overall, recorded crime fell and detections rose in Airdrie after camera installation, but in Glasgow recorded crime rose and detections fell. However, in both locations, some more specific types of recorded crimes fell and some others rose. Both schemes were pronounced successful, albeit in different ways (Ditton and Short 1999 [28]). Lighting, extra or not, is not mentioned, so any possible confounding by lighting differences cannot be ascertained. Flett (1999) [39] reported a more pessimistic view by Ditton, who said that the cameras were not cost effective, producing one arrest every 40 days. Nor had there been any sign of the investment, jobs or visitors the cameras were supposed to bring.
Munro (2000) [70] reported that the outdoor CCTV system installed in Melbourne's central business district was costly in terms of bringing offenders to justice in its initial years. Proponents of the system have since had additional funds allocated for its expansion in the belief that performance will thereby improve.
This is far from a full account of the CCTV and crime literature (eg there is more at SOCRU (2002) [104]). The virtually complete absence of lighting details is noticeable in the papers seen, precluding judgement on any possible confounding by additional lighting. Likewise, reference to the extensive high quality literature on the poor vigilance performance of humans monitoring TV screens for infrequent events seems far short of appropriate.
Video cameras with secure recording were installed in Melbourne taxis during 2002 as a reaction to passenger offences. Video frames are recorded when the brake pedal is depressed. The short distances between cameras and occupants give detailed images of the offences and offenders, better than for typical fixed installation CCTV.
Usually, near-infrared light sources are required inside cars where visible interior light for the video camera would unacceptably handicap driver vision at night. If visible-light-blocking filters are used in the cameras, the system can be relatively insensitive to the wide variation in externally incident light. Monochrome cameras are usually required, but they are less expensive than colour cameras and perform better in dim light.
Extending this technology to street CCTV systems could help to reduce any need for supplementary outdoor lighting. Cameras with greater capability at low light levels are already in use in some applications where their higher cost can be justified. Dim lighting, possibly supplemented by near-infrared sources, is already a practical surveillance option and no extra lighting at all will become so in due course.
Welsh and Farrington (2002) [116] is a review and meta-analysis of studies that deal with the effectiveness of CCTV systems in preventing crime (or more realistically, deterring, recording and detecting crime). It is both timely and systematic. Commendable effort appears to have gone into collecting as many relevant studies as possible. Of 46 reports assessed, 22 were considered rigorous enough for inclusion in the meta-analysis but four of these did not provide sufficient data, leaving 18.
Farrington and Welsh (2002a,b) [34,35] dealt at length with the Scientific Methods Score of the lighting studies reviewed but there is no mention of the Scientific Methods Score at all in their review of CCTV studies, and no explanation for this difference between the two reviews.
The main result of the meta-analysis was that CCTV reliably reduced crime overall by only 4 %. All nine of the 18 studies that showed evidence of a beneficial effect of CCTV on crime were from the UK. The other nine studies showed no evidence of a desirable effect on crime. This group included one from the UK and all of the five studies from North America. This almost parallels the lighting meta-analysis, where the overall odds ratio for the UK studies was much larger than that for the USA studies.
Welsh and Farrington stated that few of the studies attempted to control for the regression to the mean problem. From their Home Office quote that funds are made available in the UK for CCTV in town and city centres, car parks, crime hot-spots and residential areas, it seems likely that installation of CCTV is often done to try to control an existing high crime rate. Therefore many of the UK results, at least, could be affected by regression to the mean effects as a source of bias. If the bias amounts to several percent, this could readily account for much or all of the 4 % found by Welsh and Farrington for the crime-reduction effect of CCTV. It is not easy to accept that even this small effect is reliable.
The shortcomings of most of the studies often appear to be quite basic, such as having multiple confounding interventions, poor matching or even the absence of controls, unreported data (eg lighting and any supplemental lighting, and even the number of video cameras), and poor or no statistical analysis. The better studies tended to give results that were less beneficial. Poorly designed, badly conducted and inadequately reported experiments are largely a waste of research funds, which are scarce at the best of times. They tend to discredit science as a reliable and efficient way of solving practical problems. This issue appears to need much more attention and remedial action by funding agencies, academic/research centres and professional bodies in future.
Welsh and Farrington made it clear that future funding of CCTV systems should be based on high quality scientific evidence. Even if their meta-analysis result is accepted, a 4% reduction in crime seems a small payoff for the initial and operating costs of CCTV. Furthermore, there is some evidence to suggest that part of the 4% reduction in crime could merely have been spatial displacement beyond the range of individual cameras.
Perhaps the most rigorous examination so far reported for an individual CCTV study would be that of Farrington, Bennett and Welsh (2002) [36]. The result is the most counterproductive effect on crime of the 17 studies shown in the Welsh and Farrington (2002, Figure 3.1) [116] forest diagram. On this basis, there should be no more money spent on new installations of CCTV for crime prevention. Regardless, there is a good case for running the better existing studies in reverse by removing the cameras as the treatment. Justifying the expenditure to do this should not be difficult.