NIGHT SKY AND DARK ENVIRONMENTS: BEST MANAGEMENT PRACTICES FOR ARTIFICIAL LIGHT AT NIGHT ON BLM-MANAGED LANDS TECHNICAL NOTE 457 60 5.4.14 Screen Lighting Where Possible Use structures (including building eaves) to minimize light emissions beyond a developed site. Low-profile facilities, below-ground installations, and other design features can also be used to minimize light emissions beyond a developed site. These practices reduce light trespass and glare. Notes: Many situations exist for which there is no natural screening, and adding screening might be prohibitively expensive or conflict with other project goals or requirements. Added screening may affect plant and animal habitat, movement, and other behavior in unintended ways (e.g., affect predator-prey relationships). Vegetative screening is not recommended for these reasons and because vegetation may be subject to leaf drop, damage, pruning, or removal that reduces or eliminates its screening capability. 5.4.15 Use Pole-Mounted Lights with Low BUG Ratings for Backlight Close to Property Boundaries Install pole-mounted lights with a low BUG system backlight rating (e.g., B0) near site boundaries (or edges of areas requiring illumination). This practice reduces light trespass and the potential for offsite glare. Notes: Some luminaires (e.g., forward throw asymmetric luminaires) are designed to minimize backlight. The use of photometric calculations is preferred to determine luminaire locations. In some situations, it is not be possible to install lights away from a site boundary. 5.4.16 Use Forward Throw Asymmetric Luminaires Where Appropriate Use forward throw asymmetric luminaires where lights cannot be located directly above the area where illumination is needed. Forward throw asymmetric luminaires are luminaires with a light distribution pattern that casts light in an oval pattern offset from the pole such that there is minimal backlighting. These luminaires decrease light trespass and glare and concentrate light where it is needed. Notes: Forward throw asymmetric luminaires should not be used where light is needed on all sides of a luminaire (e.g., in the middle of a parking lot). The vegetation at left partially screens the unshielded light source behind it, but this screening would decrease significantly due to leaf drop, tree pruning, or tree removal. Forward throw asymmetric luminaires have a light distribution pattern that minimizes backlighting.
RkJQdWJsaXNoZXIy NTkzMzk=