City of Seattle Street Lighting Evaluation

The City of Seattle partnered with the Northwest Energy Efficiency Alliance to determine if lighting equipment choices and controls could save energy without sacrificing safety. Clanton & Associates was hired to lead this research which included community preference. Key research questions were: “Are there visibility differences between HPS and LED street lighting?” and “What is the public perception of safety with different street lighting systems?” This research stretched the boundaries of understanding regarding the visual impact of white light and found that even at 25% light level under LED lighting in dry conditions, visibility or detection distances were similar to the 100% lighting levels. These findings have profound safety implications and energy impacts for communities hoping to change their lighting system from HPS to lower wattage LED.

Scope of Work Performed

Clanton & Associates developed and conducted the street lighting visibility research project with cooperation with Virginia Tech Transportation Institute. Subjective surveys were developed and collected from over 360 local residents on the comparison of different street lighting technologies. In addition, visibility tests were performed with 134 local participants to determine object detection differences between street lighting strategies.