NIGHT SKY AND DARK ENVIRONMENTS: BEST MANAGEMENT PRACTICES FOR ARTIFICIAL LIGHT AT NIGHT ON BLM-MANAGED LANDS TECHNICAL NOTE 457 66 5.6.7 Where ADLS Technology Is Not Used, Use the Minimum Amount of Hazard Navigation Lighting Specified by the FAA For structures more than 200 ft tall that do not have ADLS technology, the minimum amount of aviation obstruction lighting specified by the FAA should be used (USFWS 2021). This practice reduces ecological effects, reduces aesthetic effects, and saves money and energy. See FAA Advisory Circular 70/7460-1L, “Obstruction Marking and Lighting,” for requirements (FAA 2015). Notes: Failure to use an ADLS where approved by the FAA can result in greater ecological and aesthetic effects. 5.6.8 Use Reduced Intensity Lights with Short Flash Durations for Hazard Navigation Lighting For aviation obstruction lighting (such as on wind turbines and communication towers), use reduced intensity lighting and lights with short flash durations that emit no light during the “off phase,” where approved by the FAA. Research shows that lower intensity flashing lighting is less disorienting to wildlife (Gehring et al. 2009), and it also prolongs the light source’s operating life while reducing energy consumption. See FAA Advisory Circular 70/7460-1L, “Obstruction Marking and Lighting,” for requirements (FAA 2015). Notes: Flashing lights may increase aesthetic and nuisance effects. Taken fractions of a second apart, these photos show a wind turbine that has a flashing red light. It is recommended that the minimum amount of aviation obstruction lighting specified by the FAA be used.
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