Section 6: Spacing of Light PolesAnchor: #i1004657
Standard Spacing for Freeways and Complete Interchange Lighting
For freeway lighting, TxDOT has standard spacings for conventional light poles to provide the minimum AASHTO-recommended illuminance levels. If higher light levels are needed, the spacing should be calculated with lighting design software.
50 ft. poles with 400W EQ LED luminaires may be spaced 270 ft. apart to provide the minimum recommended freeway illuminance levels. This will extend up to 60 ft. across the roadway from the luminaire. If wider roadways need to be lit, the spacing should be calculated with lighting design software.
40 ft. poles with 250W EQ LED luminaires may be spaced 220 ft. apart to provide the minimum recommended freeway illuminance levels. This will extend up to 50 ft. across the roadway from the luminaire. If wider roadways need to be lit, the spacing should be calculated with lighting design software.Anchor: #i1004680
Standard Spacing for Roadways Other than Freeways
To determine the required illumination levels for roadways other than freeways, use the tables in Section 2 of this chapter, the AASHTO Roadway Lighting Design Guide, or ANSI/IES RP-8-14, Roadway Lighting. An illumination program capable of calculating luminance or illuminance levels is required to determine if adequate illumination levels have been achieved.Anchor: #i1004695
Merge and Diverge Lanes
For partial interchange lighting, the first light pole for merge and diverge lanes should begin at the end of the weave area and continue to within 50 feet of the painted gore, as shown in Figure 6-2.
Figure 6-2. Typical placement for partial interchange lighting, 40 foot luminaire poles at merge and diverge lanes.Anchor: #i1004717
Lighting Near Overpasses
Poles supporting lighting for roadways beneath overpasses should be placed at least 20 feet from the overpass to reduce glare on the overpass.Anchor: #i1004727
Determining Mounting Height
Mounting height depends on the number of lanes to be lighted. The designer must use the mounting height that allows for adequate illumination levels. If proper lighting cannot be achieved with one pole, the designer should consider using additional poles to provide proper coverage.