Street Lighting for Enhancing Dark Skies (SLEDS)

Street Lighting for Enhancing Dark Skies (SLEDS) - Street lights along dark street

Project Purpose Statement

To evaluate technologies and strategies to modernize the City’s aging street light system while preserving or improving upon the dark sky status quo (visual brightness and spectral width) by evaluating the impact of different street lighting applications on its dark skies resource. The project aspires to ultimately develop an innovative street lighting standard that balances the Flagstaff community’s commitment to dark skies, sustainability and safety.

Project Background

The Street Lighting for Enhancing Dark Skies (SLEDS) Project's primary objective is to find a solution to Flagstaff's current street lighting predicament while balancing dark skies, safety and maintenance/cost effectiveness objectives.

Low Pressure Sodium

The SLEDS Project is the result of several years of discussions between the City and the local observatories (United States Naval Observatory - Flagstaff Station and Lowell Observatory) that started in May 2012. At that time, the City found itself in a lighting predicament as Low Pressure Sodium (LPS), the preferred lighting source since 1989, was becoming increasingly more expensive to purchase, quality replacement parts were becoming more difficult to acquire and the City was experiencing structural failures of the pole/mast arm connection due to the size and weight of the LPS fixture, especially in wind prone areas.


In June 2015, the Flagstaff City Council approved an Inter-Governmental Agreement (IGA) with the Arizona Department of Transportation (ADOT) to secure funding for the SLEDS Project. This was in the form of $100,000 (Fiscal Year 2016) to hire a Consultant Team (ultimately Monrad Engineering), $200,000 (Fiscal Year 2016) for test fixtures to support the Consultant Team's work, and $370,000 (Fiscal Year 2018) for the first phase of lighting replacements. All of the funding coming from the Flagstaff Metropolitan Planning Organization's (FMPO) Surface Transportation Program (STP) allocations.

Light Emitting Diode (LED) Technology

The SLEDS Project is an opportunity for Flagstaff to demonstrate to other municipalities an innovative lighting solution for dark sky preservation with LED technology that achieves municipal objectives for safety and cost effectiveness and astronomical objectives for maintaining dark skies and innovation that advances the industry or best practices for technology transfer that advances the purpose of preserving dark skies.