Outdoor Lighting and Crime - Amper

A Technical Report on the topic (ILE 2001a) recommends sign luminances that can be as
much as 100 times the luminances of floodlit building surfaces and 1000 times the luminance
of lit road surfaces (Pollard 1994). This is far too great in terms of environmental
degradation, glare effects on driver vision, as a major undesirable contribution to outdoor
ambient light and its non-uniformity, and as a potential cause of localised deep shadows. A
far more constrained approach is needed if outdoor illuminated advertising is to be tolerated at
all.
A possible starting point for sign lighting limits could be the luminance ratio when a sign is
seen in daylight against a coplanar dark matt background with reflectance of about 4%. This
gives a maximum luminance ratio of sign to background of about twenty times. At no time of
the night should any part of the sign appear more than twenty times greater in luminance than
the mean surround luminance, say. Maybe this could be simplified to a single luminance
value, such as 5 cd/m 2 , regardless of the location. This might sound drastic by comparison
with present practice, but so is the need to reduce artificial light at night. The value given is
also about ten thousand times brighter than a natural night sky background and up to hundreds
of times brighter than a typical city night sky background. Given the disruption that an
illuminated sign can cause to lighting uniformity and upward waste light in a carefully
designed minimal lighting scheme, there is a strong case for no artificial lighting of signs at
all.
Hollan (2002b) has devised a more elegant scheme in connection with the outdoor lighting
controls in the Czech Clean Air Act. The rounded upper limits for mean luminance and total
intensity depend on the area of the sign, as shown in Table 12.
TABLE 12. Maximum Luminance and
Intensity for Illuminated Billboards and Signs
Maximum
Area, m 2
Mean
Luminance,
cd/ m 2
Total
Intensity, cd
1 100 100
3 48 145
10 21 215
30 10 310
100 4 460
300 2 660
1000 1 1000
The problem needs serious consideration by a body such as the International Commission on
Illumination (CIE) so that controls will be appropriate and preferably also acceptable for
international use. The one certainty is that present excessive lighting of signs and displays
needs to be curtailed severely in the public interest, if not banned outright. Given that
company buildings are often floodlit as a form of advertising, there is no reason why such
floodlighting should escape inclusion in the necessary controls, again if such floodlighting is
to be permitted at all. Table 12 would therefore need to be extended by at least four rows,
with continuity in the three geometrical series.
110