NIGHT SKY AND DARK ENVIRONMENTS: BEST MANAGEMENT PRACTICES FOR ARTIFICIAL LIGHT AT NIGHT ON BLM-MANAGED LANDS TECHNICAL NOTE 457 51 Notes: For determining minimum safe lighting levels, engaging a qualified lighting designer may be necessary, especially for public use areas. Ensure lighting essential for safety/security is maintained. Use of an energy savings performance contract (see Section 5.1.3) may help reduce costs associated with implementing this BMP. 5.2.1.1 Consider Essential Light Sources Associated with a Built Environment Consider alternatives to permanent lighting through scheduling or relocation of tasks. For example, scheduling different outdoor tasks to be concurrent instead of at different times can reduce the duration of lighting. Relocating parking to areas immediately adjacent to a structure may allow light sharing or eliminate the need for path lighting. These practices help limit light pollution. Notes: Modifying the built environment, relocating tasks, and altering work schedules requires planning, potentially additional spending on infrastructure, and may not be feasible in some situations. Where lighting is necessary to identify structures, stairs, pathway markers, etc., determine if nonillumination solutions are adequate, such as painting curbs or steps, using retroreflective or luminescent markers, or using light-colored pavement and surfaces. Signs and markers are more visible with retroreflective or photoluminescent coating. This practice is low tech by not requiring a power source, reduces ecological and human effects, and saves installation and maintenance costs. The use of nonillumination solutions in lieu of permanent lighting is only feasible where it can be done safely and consistent with safety laws and regulations. It may not be appropriate in some situations. Depending on the technology used, some maintenance may be required (e.g., replacement of reflective tape, repainting). 5.2.1.2 Consider Nonessential Light Sources Associated with a Built Environment Lighting is often used to create aesthetic appreciation or draw attention. Often, lights are used to highlight objects or architectural features. Electronic signs are appearing with more frequency in less developed and rural areas with the intent of capturing attention. Large permanent electronic message centers or electronic billboards are an example. Electronic message centers are composed of a matrix of LED lights that are used to aim an image or message outward. The horizontal and upward light emissions cannot be shielded. Based on research by the IDA, electronic billboards can be up to 10 times brighter at night than traditional billboards. These signs can cause issues with dark adaptation and glare. The IDA has developed guidelines to minimize potential light pollution. “The primary method of mitigation is through luminance control, limiting hours of operation, and avoiding locating signs adjacent to sensitive areas or residential areas” (IDA 2019b). 5.2.2 Consider Dark Adaptation Needs of People and Wildlife Measures to promote dark adaptation for people and wildlife may include lighting upgrades (retrofitting) where there is evidence of people and wildlife being affected by existing artificial light. Adaptation considerations should be applied at all stages of management, from the development of planning schemes to the design, approval, and execution of individual developments or activities, through retrofitting of light fixtures and management of existing light trespass. Roadside electronic message center in Arizona.
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