Outdoor Lighting and Crime - Amper

what might only be chance variations. Nevertheless, displacement effects in particular still
need to be watched for, and appropriate statistical tests are available to indicate whether any
observed effects are reliable or not.
So far, displacement and diffusion in lighting and crime experiments have been searched for
in the context of the supposed beneficial effect of light. Now the issue might more reasonably
relate to whether reducing the light in a particular area will result in the displacement of crime
or diffusion of benefits to nearby areas. The amount of light in nearby areas would appear to
be no less important than in the experimental and control areas. This point appears to have
been overlooked in many existing quasi-experiments. Future experiments that include
searching for displacement or diffusion effects will need thorough before and after
photometric surveys of all areas involved as a necessary but not sufficient condition for a
reliable result.
If all that results from changing the light somewhere is just redistribution of crime, spatially
or temporally or both, then it would hardly justify use of the technique for crime prevention.
There is evidence, at least at city scales, that the net amount of any displacement and diffusion
is less than the total adverse effect of light on crime. The evidence is in Figures 1 to 3, 10 and
13: the reliable positive temporal and spatial correlations of crime and lighting is the
evidence, regardless of the lighting measure. If lighting changes resulted only in a
redistribution of crime then sizeable correlations would be chance occurrences. As it is, the
possible existence of net partial displacement of crime and partial diffusion of benefits or
disbenefits, along with international differences in these as a fraction of the total crime, could
be an explanation for the differences observed between the USA and English results in
Figures 7 and 13.
5.5.3 Lighting hotspots
Areas of crime concentration are recognised as ‘hotspots’ in criminology. This work has
identified bright lighting as a frequently associated factor, although it is not the first to point
this out in some specific cases (see Part 1). There may be some value in recognising the
existence of lighting hotspots as an entity and characterising them in terms of peopleattracting
power and photometric properties. The following examples indicate the sort of
places where such entities might occur. Under existing beliefs about lighting and crime,
lighting hotspots would result primarily from adding light to deal with crime hotspots, and
any pre-existing lighting concentrations would be seen only as sensible attempts to deter
crime at places where it might be expected to develop. In short, this would be lighting caused
by crime and the fear of crime. If a lighting concentration were not associated with high
crime at any particular time, this could be wrongly interpreted as success in deterring or
reducing crime, even if the likely increase in actual crime was still in the process of
developing.
The new hypothesis provides a broader framework for investigation and understanding of
how and why lighting hotspots come into existence. Commercial lighting such as lit signs
and window displays, light chases, strobes and decorative lighting designed to attract people
may well be the major part of a particular lighting hotspot. These light sources add to the
amount of light in the area. Their purpose has never been to repel criminals, and the existence
of any such effect now seems most unlikely. There is no reason to believe that the people
attracted will not include at least the usual proportion of criminals. Put another way, there is
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