Relationship between the reflected brightness of artificial lighting and land-use types: a case study of the University of Arizona campus

Nighttime light pollution mars the view of the night sky, wastes energy, and adversely affects ecosystems and human health. In environmental design, efforts to reduce light pollution have often focused on the use of cutoff light fixtures to direct light toward the ground rather than skyward. The results of this study, however, indicate that light-fixture-oriented solutions are not a sufficient response to the problem. The study examined the relationship between nighttime light pollution and land-use types and found that some land-use types and their associated ground materials produce reflected light that contributes to light-pollution levels. As a first step to studying the relationship of land-use types to light pollution, a new method of acquiring high-resolution (sub-30-cm resolution) nighttime aerial images was developed to depict the reflected brightness of artificial lighting with a high degree of accuracy. Once the high-resolution imagery was acquired, 11 land-use types were delineated in the study area based on inspection of daytime aerial images and site visits. Finally, land uses and the nighttime image were compared, and an association between land-use types and nighttime light pollution levels was established. The general finding is that land-use types associated with highly reflective materials, such as concrete parking structures, reflect large amounts of light, producing light pollution even when full cutoff lights are used.