Equipment: Luminaires - Road Lighting: Fundamentals, Technology and Application - page 152

Fig. 11.4 The solid angles of
the light distribution that are
the basis for the BUG
luminaire classification
system

Upwards

UH

00°

UL

UL

00°

BVH FVH

00°

FH

BH

00°

FM

BM

FL

BL

00°

Backward

0°

Forward

its B, U, and G classes, is often referred to as the BUG classification system. The
higher the luminous flux in the relevant solid angles areas, the higher the class rating.
Table 11.3 gives, as an example, the lumen values for B, U, and G classes 0, 1 and
5. The luminous flux values that determine the BUG classes are in absolute values.
This means that a lower lumen package lamp in a luminaire results in lower BUG
classes.
Some examples will serve to illustrate the practical meaning of the system. A
luminaire with a BUG classification of, for example, 102 is strongly limited as regards
its back light, emits hardly any upward light, and restricts glare reasonably well. A
BUG classification of 254 denotes reasonable backward limitation of light, very bad
upward limitation, and bad glare restriction. It should be noted that the expression
“forward” makes no distinction between the light radiated in the lengthwise and
crosswise directions on the forward or road side. In this respect it would be interesting
to combine the BUG classification system with a former CIE classification system that
distinguishes the amount of light radiated forward into different classes of throw (light
radiated in lengthwise direction) and spread (light radiated in crosswise direction)
respectively (CIE 1976 ).