Figure 6-13.Pavement brightness.
utilization for any specific situation is obtained from
this curve. The utilization curve will determine the
amount of light that actually strikes the roadway
surface. This percentage of light has an impact on the
spacing distance of the luminaries.
elevation. Thus, at any point on the diagram (or
roadway), we know the magnitude and direction of the
illumination with respect to nearby points. To make
this data more universal, you are given both the top
horizontal and left vertical axes in terms of mounting-
It is sometimes convenient for you to replot the
The isofootcandle diagram (fig. 6-14B) shows the
isofootcandle data to the same scale as that used on a
distribution of illumination on the road surface in the
drawing containing a lighting layout. By
vicinity of the luminaire.
superimposing this diagram, you can study the
distribution of light. Under the unity correction factor
The lines on this diagram connect all points having
in the mounting-height table (fig. 6-14B), one can find
equal illumination, much as the contour lines on a
the mounting height for which the data are calculated.
topographical map indicate all points having the same
The numbers beside each line represent the initial