Outdoor Lighting and Crime - Amper

Common experience is that cities are more brightly lit than their suburbs, which in turn are
more brightly lit than rural areas. The same applies to towns, their outskirts and rural areas.
Air travellers at night are often able to see these progressions at a glance. 41 The progressions
are consistent with the diminution of artificial skyglow as distance from cities and towns
increases. From the known experiences of urban blackouts and reduced crime, the important
part of the progression is not one of infrastructure, big buildings to detached houses to
isolated farmhouses, but from lots of artificial light at night to little or none. This widely
evident spatial relationship suggests a positive correlation between the amount of artificial
light and the crime rate. This does not imply causality, although it is additional evidence to
support causality. The two quantities could be mutually independent but both dependent on
population density, for example. Further evidence is needed.
As shown in Table 1, crime rates and notional skyglow growth are positively correlated over
time in each of five countries and similar temporal correlations are likely in 15 others
according to Figure 4. The crime data sets cover national populations and durations of
decades to a century. The skyglow growth curves are based on observations and cover a
century on the basis of reasonable assumptions. Their exponential form is consistent with
observations from other countries and satellites as an indicator of the accelerating growth of
outdoor ambient lighting in most places.
Street lighting reductions in certain US towns have not resulted in reported increases in crime
or road traffic accidents. Casual observations indicate that graffiti and probably other forms
of vandalism are deterred by darkness. Anecdotal reports of Dark Campus programs indicate
likewise, along with other crime reductions. Power disruptions in cities have likewise
resulted in dim conditions and reduced crime. Dim lighting or darkness therefore inhibits the
crime rate both as a spatial and temporal effect. None of this supports the notion that
insufficient light at night increases crime. Light and crime are positively correlated in the
circumstances described, 42 whatever people might say or think.
Several quasi-experiments that purport to show differently appear on examination to have too
many shortcomings for their results to be accepted as reliable. These and other experiments
are suspect for various reasons including uncertainty of treatment magnitude, unduly large
effects, financial and non-financial conflicts of interest, confounding, and hotspots regressing
to the mean independently of treatment. The collective total data for these experiments is
minuscule by comparison with the range and magnitude of the data used so far in this paper to
reveal spatial and temporal associations between lighting and crime, viz:
• populations of hundreds to hundreds of millions,
• crime data from small areas such as streets and campuses up to national scales,
41 NASA (2003) includes a photograph of London at night from the International Space
Station. The central concentration of light is beautifully shown. Satellite maps of emitted
artificial light at night, as on the cover of CPRE (2003), show the lighting progression from
city centres to rural areas.
42 As in Part 1, this document uses the standard convention that a positive correlation means
two variables change together in the same direction. Specifically, it is a positive correlation
when crime increases as lighting increases. Some criminologists use ‘positive’ to describe a
decrease in crime when lighting increases, eg Painter (1993, p 140). This practice is
deprecated.
45