PNNL

Abstract

Nighttime light emissions are increasing in most countries worldwide, but which types of lighting are responsible for the increase remains unknown. Also unknown are the contributions of public light sources such as streetlamps relative to private light sources such as advertising. Here we show that it is possible to measure the contribution of street lighting using “smart city” lighting infrastructure and satellite remote sensing. The city of Tucson, USA, intentionally altered their streetlight output over 10 days, and we examined the change in emissions observed by satellite. Streetlights operated by the city are responsible for only 13% of the total light emissions of Tucson after midnight. If Tucson did not dim their streetlights after midnight, the contribution would rise to 18%. These results suggest that sources other than streetlights are responsible for the majority of urban light emissions, and that energy and lighting policy should increasingly focus on other types of lighting sources.