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

9.4 ASSESSMENT OF REVIEW AND META-ANALYSIS
Where separate scientific experiments give differing results for a particular quantity, the
mean of pooled results generally provides a more accurate estimate. A formal review and
meta-analysis can usually do even better by rejecting poorly conducted experiments and
weighting the results of those remaining. A recent review and meta-analysis of lighting and
crime studies examined was found to include an indiscriminate mix of direct and indirect
effects. The meta-analysis result derived for a typical relighting treatment is impracticably
beneficial. This follows from the several successive treatments that would be possible
in practice, thereby allowing compounded reductions in crime well beyond anything likely
on present indications. This error appears to have arisen because of inadequate photometric
quantification of lighting treatment, contrary to warnings in the 1977 and 1997 reviews
mentioned in Section 9.1 above.
Of the 13 studies included in the meta-analysis, serious procedural or analytical shortcomings
or both were found in at least five of them. Photometric aspects are inadequately
presented in all of these five studies also. A consequence is that researchers failed to recognise
when systematic and other errors led to false or overlarge beneficial effects. Removal
of suspect studies from the meta-analysis brings the weighted average result much closer to
a null effect. Forcing the upper limit for the 95% confidence interval to have a realistic value
leads to a null result if all studies are included. It appears that a counterproductive effect of
lighting on crime would emerge from discarding the five problematical studies and applying
corrections for the various forms of bias thought likely to have acted in some or all of the
remaining studies.
The best that can be concluded at this stage is that there appears to be no compelling
evidence for any appreciable net direct beneficial effect of increased outdoor lighting in
reducing actual crime at night or for net indirect beneficial effects by night or day. National
lighting standards should not state or imply that outdoor lighting has any value for crime
prevention or deterrence.
9.5 DEBUNKING THE MYTH OF LIGHTING FOR CRIME PREVENTION
To the extent that outdoor lighting is intended to prevent crime, its capital and operating
costs appear to be a waste of public and private funds. It may even be counterproductive.
In the case of industrial and commercial infrastructure, the cost burden reduces industrial
competitiveness and hinders economic growth.
News media have uncritically perpetuated the myth of increased lighting for crime prevention.
Journalists and others concerned need to check the facts more carefully. An extensive
pro-lighting campaign started in the 1990s appears to have swayed many UK authorities
to install brighter outdoor lighting as a supposed crime reduction measure. The UK Crime
and Disorder Act 1998 may have accelerated this process. In the year ending April 2002,
street crime in the UK was reported as having increased by 28 %, quite inconsistent with the
claimed crime-prevention effect of lighting.
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