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3 Background Light-emitting diodes (LEDs) are being used increasingly for many different safety-related applications including exit signs (Boyce 1994), road traffic signals (Conway and Bullough 1999), vehicle brake and turn lights (Olson 1987), street lighting (Radetsky 2010), and airfield lighting. LEDs have several characteristics that make them especially attrac- tive for visual signaling applications (also see Appendix A for a description of LEDs and comparisons between LED and incandescent sources): ⢠Durability and longevity as solid state devices ⢠Wide range of available colors (including all aviation signal light colors) ⢠Narrowband wavelength output resulting in saturated color appearance ⢠Relatively low energy requirements ⢠Immediate âswitch-onâ and âswitch-offâ time. The primary incumbent lighting technology on most airfields, incandescent filament-based lamps, tend to have shorter useful operating lives than LEDs. Typical operat- ing lives for incandescent lamps are on the order of a few hundred to a few thousand hours (Bullough 2000). In com- parison, well-designed LED lighting systems can last tens of thousands of hours. Incandescent lamps also tend to have lower luminous efficacy (lumens per watt, lm/W) than LED light sources, resulting in relatively higher energy requirements. Energy legislation such as the Energy Independence and Security Act (EISA) of 2007 is accelerating the development of alternatives to conventional incandescent lighting systems for many light- ing applications, largely because of the relatively low lumi- nous efficacy of incandescent lamps. Although the EISA does not impact airfield lighting directly, the rapid development of alternatives to incandescent lamps for general lighting has contributed to substantial interest in and use of LED signal lighting on airfields in the United States. Some differences between LEDs and incandescent tech- nologies might be perceived as possible impediments to the more widespread use of LED airfield lighting. The narrow- band spectral output of LEDs means they do not produce infrared energy (heat) that might be useful in melting snow and ice build-up during very cold weather. LED airfield fixtures must work with the existing specialized electri- cal infrastructures of airfield lighting. In addition, because LED fixtures are, at present, relatively expensive in terms of initial cost compared with incandescent systems, there can be concerns about whether the technological advantages of increased operating life and reduced energy use will enable airports to recover initial investments when using LED light fixtures. The present synthesis study was conducted through ACRP of TRB to gather information from the literature and from airports and other organizations with experience using LED airfield lighting, and to help airport operations and maintenance personnel consolidate and sift through the issues related to this emerging technology. The lessons learned by airports that have used this technology in air- field lighting will be useful to other organizations facing the question of whether, or when, to install LED airfield light- ing, what questions to ask, and what benefits or problems might be anticipated. Methodology To gather the information synthesized in the present report, two primary methods were used, a literature search and a survey of organizations having experience with LED airfield lighting. literature Search A literature review was conducted to identify examples of air- ports and other organizations that had used or were planning to use LED airfield lighting. Sources that were reviewed for this information included suggestions from ACRP Synthesis Topic Panel members for this study, the Transport Research International Documentation (TRID) database maintained by TRB (http://trid.trb.org), and databases of trade publica- tions, newswires, and press releases (e.g., ProQuest ABI/ INFORM, Gale Business and Company Resource Center, Reed Elsevier Lexis-Nexis). Information was reviewed and organized by different top- ics such as installation issues, operation and maintenance, and economics, and is presented in subsequent chapters of this synthesis report. chapter one IntroductIon
4 Survey Questionnaire With assistance from the members of the Topic Panel, U.S. airports with experience using LED airfield lighting were identified for possible participation in a survey (Appendix B contains the survey questionnaire and results). Individuals from these organizations were contacted to confirm their will- ingness to participate; 22 agreed to participate and all 22 com- pleted the survey, for a 100% participation rate (Appendix C lists participating organizations, as well as other airports that are known to have installed LEDs). Figure 1 summarizes the types of airports represented among survey participants. The survey was distributed individually as a text docu- ment (Microsoft Word); participants could enter their responses directly into the document and return by means of e-mail, or print the document and complete the survey by hand (and fax or scan and e-mail the completed form). Participants were also given the opportunity to complete the survey by telephone. The survey was administered during the summer and autumn of 2011. In addition to the 22 survey participants from the United States, two additional surveys were completed by European airports. Their responses are not included in the survey results in Appendix B, but were consistent with those of the U.S. respondents. report content Following a short chapter summarizing current practices and challenges with LED airfield lighting, this report is struc- tured according to the primary issues identified in the litera- ture search and survey questionnaire: ⢠Installation issues, ⢠Operation and maintenance issues, and ⢠Economics. These topical chapters are followed by a chapter contain- ing the primary findings, conclusions, and outlook for LED airfield lighting, including practical guidance airports can use in decision making. FIGURE 1 Distribution of airport types among survey participants.
