NIGHT SKY AND DARK ENVIRONMENTS: BEST MANAGEMENT PRACTICES FOR ARTIFICIAL LIGHT AT NIGHT ON BLM-MANAGED LANDS TECHNICAL NOTE 457 61 5.4.17 Choose Roadway Luminaires to Maximize Lighting the Road and Minimize Lighting Away from the Road When choosing roadway luminaires, maximize the proportion of light emitted on the road, and minimize the proportion emitted off the road (i.e., use luminaires with a low backlight rating in the BUG rating system). These luminaires decrease light trespass and glare away from the road and concentrate light where it is needed. Notes: Many roads on BLM-managed lands neither have nor require lighting. Engage a qualified lighting designer where road lighting is needed for safety. 5.4.18 Use Lighting Transition Zones between Brightly Lit and Unlit Areas Use lighting transition zones to create smooth, gentle transitions between brightly lit and unlit areas to avoid deep shadows and minimize effects on dark adaptation. This practice can improve safety by avoiding glare and improving dark adaptation. Notes: The use of lighting transition zones requires careful design to provide enough safety illumination for public use areas and may result in an increase in the number of luminaires. 5.4.19 Leave Gaps in Long Linear Arrangements of Lights Where possible, leave gaps in long linear arrangements of lights (such as along a roadway) to avoid impeding animal movement. Research shows that bats and other species may avoid lights, and their movement may be restricted by a “barrier” of lights. Notes: This practice could have aesthetic or safety effects if not executed properly. 5.4.20 Provide Dark Corridors to Facilitate Animal Movement Design and integrate dark corridors to encourage/ guide animals away from or around illuminated areas (such as roads). Orient corridors relative to other landscape features and along likely commuting routes for animals (e.g., along hedgerows, heavily vegetated and low-volume roadways, stream courses). To be more effective, it is recommended that dark corridors: • Link to existing paths, foraging areas, and other important habitat. • Contain mature vegetation to provide shelter from predators and weather. • Contain native plant species to attract insects for foraging. • Be located away from roads. • Be consistently maintained (i.e., kept dark). Notes: This practice could conflict with safety and transportation requirements or other needs. Resolve conflicts to adequately address issues regarding safety and transportation requirements. 5.5 BMPs for Light Color Matters: Select Amber, Orange, or Red When Possible The following BMPs address lighting of the appropriate color temperature for the task at hand, while minimizing environmental impact. A long linear array of lights can impede animal movement by creating a barrier of lights.
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