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CHAPTER 6 Roundabouts, Interchanges, and Intersections Current Guide The current AASHTO Roadway Lighting Design Guide (AASHTO 2018) discusses the lighting of roundabouts, pole placement, and the extent of the lighting system. It recommends 1.3 to 2 times the lighting level of the highest illuminated approach road and extending the light levels 6 to 10 ft (1.8 to 3.0 m) outside the outer curb to the sidewalk or other roadside features. This chapter in the guide does not address intersections and interchanges, which are included in Chapter 3 of the current AASHTO guide. Complete interchange lighting is designed to the same levels as the roadway, but no light level requirements are given for partial interchange lighting. Light levels for intersections are recommended to be equal to the sum of the two intersecting roadways. The guide also includes recommendations for crosswalk lighting at intersections where vertical lighting levels along the centerline of the crosswalk at 5 ft (1.5 m) in height would be equal to the horizontal levels being provided. Additional Considerations When Using LED Sources Existing AASHTO recommendations would not change for LED sources. Meeting the AASHTO recommendation of lighting 6 to 10 ft (1.8 to 3.0 m) outside the outer curb would provide enough surround lighting, which can sometimes be limited with LED optical systems. Additional considerations for LED luminaires include ⢠Use of 4000K CCT sources to assist in the detection distance for pedestrians and hazards at these facilities, ⢠Levels for adaptive lighting at the facilities that vary with the approach roads, and ⢠Vertical lighting levels in crosswalks at roundabouts that meet the same requirements as crosswalks at intersections. Key Issues for Roundabouts, Interchanges, and Intersections ⢠Consider 4000K CCT sources for roundabouts, interchanges, and intersections. ⢠Consider vertical lighting requirements in all crosswalk locations. 36
