Flagstaff Highway Lights Converted to 'Dark-Sky Friendly LEDs'

The Arizona Department of Transportation (ADOT) has completed a pioneering highway lighting upgrade in the Flagstaff area, replacing more than 370 high-pressure sodium fixtures with amber LED lights designed to preserve the region’s famously dark night skies while maintaining road safety. The $1.1 million project is the first deployment of amber LEDs on U.S. interstate highways.  

The new lighting has been installed at all Interstate 17 and Interstate 40 interchanges in Flagstaff, including the junction connecting the two highways, as well as along sections of Milton Road and Historic Route 66. The amber LEDs were selected after years of testing and collaboration between ADOT, the City of Flagstaff, astronomers, and the Flagstaff Dark Skies Coalition.  

Unlike conventional white LEDs, the amber fixtures emit less blue light, significantly reducing skyglow that interferes with astronomical observations and impacts wildlife. Flagstaff, home to the Lowell Observatory and the U.S. Naval Observatory, became the world’s first International Dark Sky City and continues to lead efforts to balance public safety with environmental and scientific priorities.  

Officials say the project demonstrates that energy-efficient roadway lighting and dark-sky preservation can coexist. The initiative may serve as a model for other communities seeking to reduce light pollution without compromising nighttime visibility for motorists, cyclists, and pedestrians.