outdoor lighting and crime, part 1 - Astronomical Society of Victoria

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-lightblocking
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.
7.3.2 Review and meta-analysis of CCTV and crime studies
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
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