Table 6-1.Roadway Illumination and Lamp Selection Guide.
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 manufacturers
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
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 normal