Lighting Quality Parameters - Road Lighting: Fundamentals, Technology and Application - page 93

Fig. 8.2 Basis for the G
classification system for the
glare restriction of luminaires
employed in residential areas

I 90

I 80

I 70

8.2.3 Lighting of the Surrounds

For lighting of the surrounds, the lighting quality parameter is the vertical illuminance
at the positions of those planes that need to be sufficiently bright. These are usually
the facades of houses near to the path of the pedestrian or cyclist. Sometimes, the
average vertical plane illuminance, E plane,av (or E facade,av ), is used as the lighting
quality parameter, and sometimes the absolute minimum plane illuminance, E plane,min
(or E facade,min ).

8.2.4 Glare Restriction

The concept of threshold increment (TI) used for the restriction of glare for motorized
traffic can also be used for the same purpose for cyclists and pedestrians in those
situations where they can be expected to have defined viewing directions along the
street and/or along the pavement. Where viewing directions are more random (e.g.
directly into bright luminaires), a different concept is needed. A limitation of the
luminous intensities of the luminaires in critical directions can limit discomfort glare
under these conditions. As a criterion, the maximum luminous intensities at angles
of elevation of 70 ⓦ ,80 ⓦ and 90 ⓦ

is therefore sometimes used (Fig. 8.2 ):

I max at 70 ⓦ and I max at 80 ⓦ and I max at 90 ⓦ

CIE defined so-called luminaire “luminous intensity classes” (G1 to G6) on the basis
of these intensities. The exact classes are given in Chap. 11, Table 11.2.
The discomfort effect of a road-lighting luminaire is in fact not only dependent
on its luminous intensities but also on the light-emitting area of the luminaire. A
lighting quality parameter that takes into account both the luminous intensity and
the bright-area effect is the luminaire glare index. This has already been defined in
Sect. 5.2.3 as:

I 85
A 0 . 5

=

luminaire glare index