Standards and Recommendations - Road Lighting: Fundamentals, Technology and Application - page 101

Table 9.7 Values of the average horizontal illuminance (maintained) after applying mesopic correc-
tion factors of Table 6.3 in dependence of S/P ratio. Corrected values only permitted when Ra ≥ 60.

Basis: high-pressure sodium lamps (S/P ratio = 0.6)

E hor,av (lux)

S/P = 0.6 S/P = 1.0 S/P = 1.4 S/P = 2.2

Class P1 15 14.4 13.8 12.8

Class P3 7.5 7.1 6.6 5.9

Class P6 2.0 1.8 1.6 1.3

9.1.5 Adaptive Lighting

The traffic characteristics that determine the lighting quality required, as defined by
the weighting values of Tables 9.2 and 9.5 , may vary during the course of the evening
and night, allowing for periods with reduced lighting level. The CIE recommendation
explicitly mentions adaptive lighting that adapts itself to temporarily-changing cir-
cumstances such as traffic, weather and ambient lighting conditions as a possibility
to significantly reduce energy consumption. If the lighting installation is designed
such that the lighting level can, indeed, be adapted (dimmed), important reductions
are possible. It is important to note that under such circumstances only the lighting
level should be lowered, not the uniformity. Switching off individual luminaires is
therefore not a possibility.

9.2 European Standard

The first European Standard for road lighting published by the European Committee
for Standardization (CEN) was published in 2003. In 2014 or 2015 a completely
revised version will be published. In this Section we will consider the draft version
for public comment, prEN 2013, of this revised standard (CEN 2013a , b ). It is based
largely on the CIE system described above. Therefore only the main points of the
European standard will be described here.

9.2.1 Lighting for Motorized Traffic Routes

The European system uses the same six lighting classes (M1-M6) as used by the
CIE. The lighting values for each of these classes are specified in draft Standard EN
13201-2 “Road Lighting—Part 2: Performance requirements” (CEN b ). The required
values for the criteria L av ,U o ,U l and TI are exactly the same as those required by
CIE as already given in Table 9.1 , but with just one exception (Ul l for M6). So, the
lighting level range is from 2.0 to 0.3 cd/m 2 from class M1 to M6.