Section 6: Spacing of Light PolesAnchor: #i1004657
Standard Spacing for Freeways and Complete Interchange Lighting
For freeways, poles (illumination assemblies) for conventional lighting should be spaced as shown in Figure 6-5.
Figure 6-5. Recommended spacing for freeway and complete interchange lighting.Anchor: #i1004680
Standard Spacing for Roadways Other than Freeways
To determine the required illumination levels for roadways other than freeways, use An Informational Guide for Roadway Lighting, available from AASHTO (see References in Chapter 1, Section 1, for information on obtaining the publication). 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 6-6.
Figure 6-6. 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.Anchor: #i1004737
Transition lighting is a technique intended to provide drivers with a gradual reduction in lighting levels and glare when leaving a lighting system. The use of Transition lighting is not generally recommended for TxDOT projects.
If transition lighting is used, the techniques for providing a transition are many and can be applied to all types of lighting systems with varying degrees of complexity.
For further information on transition lighting see:
- ANSI RP-8-00
- Lighting Handbook Reference and Application
- An Informational Guide on Roadway Lighting
See References in Chapter 1, Section 1, for information on obtaining these publications.