|Advancing the effective use of light for society and the environment. |
| Tuesday, April 6, 2004 |
Field study proves success of fluorescent technology for streetlighting in a rural community
Prototype fluorescent streetlights installed along Clark Street in Easthampton, Massachusetts
Residents and town officials of the rural community of Easthampton, Mass., recently helped the LRC complete a field study regarding the application of fluorescent lamps in streetlights. The purpose of the project was to demonstrate how to use a newly developed photometry system for streetlighting and to combine a design for increased visibility with energy efficiency. The U.S. Environmental Protection Agency sponsored this project with cooperation from Western Massachusetts Electric Company (WMECO), the Town of Easthampton, and Magnaray International. Dr. Yukio Akashi, LRC senior research scientist and assistant professor, and Peter Morante, LRC director of energy programs, evaluated the replacement of high-pressure sodium (HPS) lamps with fluorescent streetlamps along residential Clark Street over a period of several winter months.
New photometry system sets the stage
A closer view of the prototype fluorescent fixture
Dr. Akashi’s premise for the study was a demonstration of a new photometric system, developed by Dr. Mark Rea and LRC colleagues, for mesopic conditions (low light levels), such as encountered while driving at night. Akashi explained that humans have two kinds of receptors in the retina—cones and rods. The standard photometry system accounts for only cones that function mainly at photopic light levels (daytime conditions), such as in daylit spaces. “However, the current photometry does not always work well at mesopic light levels, where rods are also involved. Since the peak wavelength sensitivity of rods is shorter than it is for cones, human color sensitivity shifts toward shorter wavelengths, making us more sensitive to bluish light,” he said.
Akashi hypothesized that streetlamps utilizing HPS technology, which contain relatively longer wavelengths, are not adequate for mesopic conditions and underestimate human color sensitivity. The fluorescent lamps utilized in this study were chosen because they emit high concentrations of short-wavelength blue light. Akashi theorized that these lamps would be more optimally tuned to mesopic conditions, thus reducing energy without impairing, or perhaps even improving, nighttime visibility of drivers and pedestrians.
The study began in October 2003 and ran through the end of January 2004. Prior to the installation of the new lamps, Easthampton’s mayor, Michael Tautznik, (or “Mayor Mike” as he is referred to by residents) and WMECO assisted Akashi and Morante with mailing questionnaires to 70 residents of Clark Street. The questionnaire asked residents about their perceptions of the general street appearance lit by HPS lamps, including visibility, brightness vs. gloominess, and color appearance, as well as how the lamps were observed by the respondents when they were driving and walking.
In early October the LRC and WMECO replaced seven of the 19 existing HPS lamps along Clark Street with prototype fluorescent fixtures developed by Magnaray International. Study participants were then asked to spend a few weeks observing the new lighting in their neighborhood before filling out a questionnaire similar to the one they had previously received. The second questionnaire was delivered during the first week of January. After the survey, the conventional HPS lighting was restored to Clark Street.
Residents give positive ratings for the new streetlights
Results from the survey supported Akashi’s hypothesis. The responses revealed that on all 18 questions, respondents rated the fluorescent streetlight technology as better than the conventional HPS lamps. Among other positive responses, Clark Street residents reported that they perceived the new lamps as increasing visibility, driver and pedestrian safety, and general attractiveness of the road, as well as the surrounding landscaping. Other positive qualities attributed to the fluorescent lamps included brightness, a “less gloomy” appearance, and an increased sense of security and safety.
In terms of energy savings, Akashi stated that the fluorescent lamps used 30 percent less energy compared with the HPS lamps.
Peter Morante noted that, “The Easthampton Streetlighting study was a real success, not only in terms of expected results, but also in the collaborative efforts among federal and local government agencies, the utility company, the manufacturer, and private citizens.”
The Lighting Research Center (LRC) is part of Rensselaer Polytechnic Institute and is the leading university-based research center devoted to lighting. Founded in 1988, the Lighting Research Center has built an international reputation as a trusted and reliable source for objective information about lighting technologies, applications, and products. Its mission is to advance the effective use of light and create a positive legacy of change for society and the environment.
© 2004 Rensselaer Polytechnic Institute, Troy, NY 12180 USA.