Until recently, roadway lighting technologies changed very slowly. Technologies like high pressure sodium (HPS) and other high intensity discharge (HID) lamps used in cobra head-style fixtures were state-of-the-art for decades. In response, the best practices for roadway lighting design had remained largely unchanged since the 1970s and 1980s. A growing concern for preventing light pollution in the 1990s and 2000s morphed the dropped lenses of cobra head fixtures to flat glass windows, but this did not fundamentally change lighting design methods and standards, and tried and true tools for roadway lighting design from a generation ago continued to be useful.
Fast forward to 2014, and the roadway lighting landscape is changing rapidly. Agencies responsible for designing and maintaining safe roadways have a bewildering array of options for roadway lighting design including not only HPS systems that still make up the majority of roadway illumination systems on roads, but also light emitting diode (LED) technologies, new forms of ceramic metal halide (CMH) lamps, fluorescent induction lamps, and plasma light sources. Controls for these lighting systems are making dimming and switching easier as well, so street lights don't need to burn continuously from dusk to dawn as they have for decades. Unfortunately, there has been a lack of objective information available regarding current options for sustainable roadway lighting.
In collaboration with the New York State Energy Research and Development Authority (NYSERDA) and the New York State Department of Transportation (NYSDOT), the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute conducted three "Sustainable Roadway Lighting" seminars across New York State for NYSDOT engineers, local municipalities, electric utilities, and lighting specifiers. Instructors John Bullough and Leora Radetsky, LRC scientists, shared the basics of roadway lighting, techniques for evaluating different lighting technologies, new ways to quantify the efficiency and effectiveness of roadway lighting, and upcoming concepts that may transform how roadway lighting is practiced.
The LRC has developed a guidebook containing the seminar content, which is a useful reference tool for seminar participants and non-participants alike. Download the free guidebook here.