US Highway 101 LED Lighting Case Study
Drivers along U.S. Highway 101 west of Olympia, Washington enjoy whiter light and greater uniformity as the result of the first LED lighting system installed along an American freeway. The Washington State Department of Transportation (WSDOT) installed 88 Autobahn ATB2 luminaires from American Electric Lighting® (AEL) along a 1.3 mile stretch of roadway near Black Lake Boulevard as a pilot project.
The new LED system replaces the previous high-pressure sodium (HPS) system, which costs WSDOT an estimated $3.9 million statewide in utility costs annually. The LED lighting system incorporates the ROAM® system from Acuity Brands®, allowing WSDOT to remotely monitor luminaire performance and control light output based on traffic levels.
WSDOT’s maintenance program funded the lighting retrofit based on anticipated energy and maintenance savings. The department estimates LED technology with dimming controls will save more than $75,000 in maintenance and operating costs over the life of the system (approximately 15 years) compared to standard HPS luminaires. The new technology will also reduce energy consumption by more than 1.7 million kilowatt-hours of electricity.
Autobahn fixtures were installed on existing 40-foot metal poles that include 16-foot mast arms, with the LED fixtures replacing the HPS units one-for-one. To save energy, WSDOT remotely switches off 66 of the 88 LED luminaires between 11 p.m. and 5 a.m. The other 22 fixtures at ramp connections and intersections on Black Lake Boulevard remain illuminated overnight.
WSDOT currently targets average illuminance levels of 0.6 footcandles for the entire roadway during peak period operation. During non-peak period operation, WSDOT targets 0.6 footcandles at the ramp connections and intersection areas only.
Using ROAM, WSDOT dims the fixtures by 30 percent at initial installation and gradually increasing the input power to compensate for LED lumen depreciation over time. This provides WSDOT with additional energy savings and ensures light levels are constant throughout the fixtures’ service life.
WSDOT will clean the Autobahn LED fixtures in six years and evaluate the luminaires at that time to determine when they will require maintenance. Engineers expect the LED system to last 12 to 15 years without maintenance—beyond the 6 year cleaning—compared to four years for the high pressure sodium luminaires.
WSDOT will likely increase use of LED lighting as national standards continue to evolve and costs for LED lighting decrease.
