Standards and Recommendations - Road Lighting: Fundamentals, Technology and Application - page 248

Table 17.1 Environmental lighting zones. (CIE 2013 )
Zone Lighting environment Examples

E0 Intrinsically dark Unesco starlight reserves, IDA dark-sky parks

E1 Dark Relatively-uninhabited rural areas

E2 Low district brightness Sparsely-inhabited rural areas

E3 Medium district brightness Well-inhabited rural and urban areas

E4 High district brightness Town and city centres, commercial areas

The CIE has developed a system for dividing areas into different environmental
zones according to the typical brightness of their environment. This system is used
in many international, national and local regulations, sometimes in a modified form
to suit local circumstances. In the latest CIE recommendation, five different environ-
mental zones (E0 - E4) are defined (CIE 2013 ). Table 17.1 gives the CIE definition
of these five zones together with examples of areas for each zone. The Lighting-Zone
system defined jointly by the International Dark Sky Association (IDA) and the Il-
luminating Engineering Society of North America (IESNA) also uses five different
zones, which are labelled LZ0 - LZ4. They are similar to the environmental zones
of the CIE.
Most regulations for the limitation of light pollution make use of the principle of
curfew to take into account the effect of severity in relation to time in the evening or
night. Before curfew, the regulations are more relaxed than after curfew, when they
are more stringent. This enables, for example, sports lighting installations to be used
before curfew but no longer after curfew. The same curfew principle is also often
used in regulations governing decorative outdoor lighting installations. The before-
and-after curfew lighting specifications are given in the light-pollution standards, but
the exact timing of the curfew is usually not specified here. The timing of curfew
is very much seen as a local responsibility and is usually given in municipality or
other local governmental regulations. Of course, after-curfew regulations should not
be specified for lighting that serves to promote safety or security - as, for example,
road lighting.

17.2 CIE Guide

In 2003 CIE published the “Guide on the limitation of the effects of obtrusive light
from outdoor lighting installations”. In 2015 a completely updated version of this
Guide will be published. The information given here is based on the 2013 draft
(CIE 2013 ). The guide specifies maximum values for the light-pollution parameters,
described in the previous chapter, for each of the five environmental zones (E0 - E4)
defined in Table 17.1 . For some parameters the values specified are different for pre-
curfew and after-curfew hours. As an example, the values for environmental zones
E0, E2 and E4 are given in Table 17.2 .