Outdoor Lighting and Crime - Amper

5. THE HYPOTHESIS AND FURTHER EVIDENCE
5.1 LIGHTING CONSTRAINTS AND CRIME IN SAN DIEGO
San Diego, CA, has had low-pressure sodium (LPS) as a large proportion of its outdoor
lighting 54 for many years to try to minimise the adverse effect of its outdoor lighting waste 55
on the performance of the 5-metre (200-inch) Hale telescope on Palomar Mountain. Palomar
and the Mount Laguna Observatory as well are both within 100 km of San Diego. Stray light
from San Diego is the major source of artificial skyglow affecting the Hale telescope
(Garstang 1989a). San Diego has been one of only a handful of places in California where
light pollution, light trespass and glare have been addressed reasonably in the municipal code
and in the county zoning ordinance, although over sixty other places in California are thinking
about it (Skykeepers 2003).
San Diego is about 130 km from Los Angeles, which has three times the population. Using
FBI (1998) Uniform Crime Reports (UCR) data, San Diego has a crime rate that is lower than
for Los Angeles (11% lower for 4.51% against 5.07% for the respective cities, or 9% lower
for 3.95% against 4.33% for the respective Metropolitan Statistical Areas). The difference is
much larger when account is taken of the threat posed by the various crimes, as in the Morgan
Quitno crime scores mentioned in Section 3.2.6 above.
San Diego is ranked 123 for crime safety on the Morgan Quitno (2000) list of 315 US cities
with populations above 75 000. Los Angeles is ranked 222 (ie, less safe) on this same list.
Differences in the Morgan Quitno scores and rankings are also in the direction expected on
the basis of the new hypothesis, given that San Diego has had outdoor lighting constraints that
have not been applied generally in Los Angeles.
San Diego recently decided to replace most of its 50-W low-pressure sodium streetlights by
brighter, less well-shielded and more energy-consuming 150-W high-pressure sodium lights,
supposedly to make the place safer for pedestrians at night (WalkSanDiego 2002) as part of
the city’s growth strategy. This change was applied to within 50 km (30 miles) of Palomar
despite strenuous objections by environmentalists and professional and amateur astronomers
(eg Johnson 2001). More recently, the change was extended to within 25 km (15 miles) of
Palomar (Monteagudo, 2003). The change is likely to be good for business, considered in
isolation. From Part 1, the change is also likely to be futile at best for direct crime deterrence
at night and environmentally damaging. According to the new hypothesis, as San Diego’s
lighting characteristics move towards parity with those of the more conventional lighting in
54 As LPS light is mostly confined to a narrow part of the visible spectrum, a narrow-band
rejection filter at the telescope can diminish adverse effects of backscattered sodium light on
image contrast.
55 No such consideration is mentioned in the description of the fitting of 895 QL induction
light sources in the San Diego Gaslamp Quarter, the largest such installation in the USA
(Philips no date). The unshielded diffusing-globe luminaires appear to emit more than half of
the available light above the horizontal, wastage that is highly inappropriate anywhere
outdoors, let alone in a ‘showcase’ example.
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