NIGHT SKY AND DARK ENVIRONMENTS: BEST MANAGEMENT PRACTICES FOR ARTIFICIAL LIGHT AT NIGHT ON BLM-MANAGED LANDS TECHNICAL NOTE 457 55 5.3.4 Use Aircraft Detection Lighting System (ADLS) Technology for Hazard Navigation Lighting Where approved by the FAA, aircraft detection lighting system (ADLS) technology is an option for aviation obstruction lighting on structures taller than 200 ft (USFWS 2021). An ADLS is a radarbased obstacle avoidance system that activates aviation obstruction lighting only when an aircraft is proximate to an obstruction on which this technology is mounted, such as a wind turbine. The obstruction lights are inactive when aircraft are not in proximity to the obstruction. The use of ADLS technology greatly reduces the negative aesthetic effects of lighting from tall structures and should also reduce avian mortality. It also reduces wasted energy and prolongs the life of obstruction lighting. Notes: ADLS technology costs substantially more to purchase and install than conventional “always-on” lighting. Consider laws and regulations from the FAA and other agencies that govern lighting practices when designing facility lighting. Only ADLS technology that meets the requirements of Chapter 14 of FAA Advisory Circular 70/7460-1L, “Obstruction Marking and Lighting” (FAA 2015) should be used. FAA consultation may be required or desirable in the early stages of facility lighting design. An ADLS may be inappropriate in some situations (e.g., when the facility is located close to an airport). 5.4 BMPs for Lighting Only Where Needed The following BMPs address directing lighting only where needed for safety and task completion. 5.4.1 Direct Light Only Where It Is Needed Luminaires should be selected, sited, and the light they produce directed so that they illuminate only the area needed to support a particular task (e.g., parking, driving, walking, working). All light directed where unneeded is wasted light that may cause various types of light pollution. Use luminaires that meet the IES TM-15-20 BUG ratings (IES 2020) for the applicable lighting zone performance standard (see Sections 5.1.2 and 5.4.5). Directing light only where it is needed reduces offsite light trespass and glare and may also decrease skyglow and light clutter. It may also improve safety and security in over-lighted/glare situations and save energy that would otherwise be wasted. Notes: Some lights cannot be pointed in a particular desired direction because of the luminaire design. These lights should be avoided, where possible. Modern LED luminaires can often be aimed with great precision. An ADLS radar unit mounted on a meteorological tower at a wind energy facility. Federal Aviation Administration This plaza at the Lowell Observatory is properly lit to provide enough light where it is needed for safe enjoyment of the outdoor area and to navigate to adjacent buildings and parking areas.
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