The current recommended practice (ansi/iesna rp-8) calls for uniform luminance on the roadway surface. This paper summarizes the results of an investigation to determine the effects on the luminance-producing ability of luminaire distributions as various distribution factors were changed while other variables were held constant. It was concluded that (a) the luminance-producing ability of the distribution increases as the vertical angle of the beam maximum increases; (b) in a bidirectional distribution, the maximum luminance-producingability was obtained when the luminaire, the point to be lighted onthe roadway, and the driver were all in line; (c) as the lateral angle of the beam maximum decreases, the luminance-producing ability of the system decreases; and (d) the luminance-producing ability of light toward the driver is much greater than that of light away from the driver (as much as 10 times under certain circumstances), which makes a "counterbeam" system practical. This paper appears in transportation research record no. 1247, Visibility criteria for signs, signals, and roadway lighting.
Samenvatting