Table 6-1. - Roadway Illumination and Lamp Selection Guide.
|Area Class||Roadways Classification||Min. Average. Maint. FC||Uniformity Avg./Min. FC/FC|
pedestrian volume and a continuously heavy demand for off-street parking during business hours.
Intermediate: That portion of a municipality which is outside of a downtown area but generally within the zone of influence of a business or industrial development; characterized often by a moderately heavy nighttime pedestrian traffic and a somewhat lower parking turnover than is found in a commercial area. This definition includes military installations, hospitals, and neighborhood recreational centers.
Residential: A residential development, or a mixture of residential and commercial establishments, characterized by few pedestrians and a lower parking demand or turnover at night. This definition includes areas with single-family homes and apartments.
SELECTION OF LUMINAIRES
Luminaries are designed to provide lighting to fit many conditions. For street and area lighting, five basic patterns are available, as shown in figure 6-11. While many luminaries can be adjusted to produce more than one pattern, no luminaire is suitable for all patterns. Care must be used, especially in repair and replacement, to install the proper luminaire for the desired pattern, as specified in the manufacturer's literature. Even when the proper luminaire is installed, care must be used to ensure that all adjustments have been properly made to produce the desired results.
Type I (fig. 6-11a) is intended for narrow roadways with a width about equal to lamp-mounting height. The lamp should be near the center of the street. A variation of this positioning (fig. 6-11b) is suitable for intersections of two such roadways with the lamp at the approximate center.
Type II (fig. 6-11c) produces more spread than does Type I. It is intended for roadways with a width of about 1.6 times the lamp-mounting height with the lamp located near one side. A variation (fig. 6-11d) is suitable for intersections of two such roadways with the lamp not near the center of the intersection.
Type III (fig. 6-11e) is intended for luminaries located near the side of the roadway with a width of not over 2.7 times the mounting height. Type IV (fig. 6-11f) is intended for side-of-road mounting on a roadway with a width of up to 3.7 times the mounting height.
Type V (fig. 6-11g) has circular distribution and is suitable for area lighting and wide roadway intersections. Types III and IV can be staggered on opposite sides of the roadway for better uniformity in lighting level or for use on wider roadways.
MOUNTING HEIGHT AND SPACING
There are two standards for determining a preferred luminaire mounting height: the desirability of minimizing direct glare from the luminaire and the need for a reasonably uniform distribution of illumination on the street surface. The higher the luminaire is mounted, the farther it is above the normalContinue Reading