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3 CHAPTER ONE INTRODUCTION BACKGROUND of replacement, may lead to LED signal modules remaining in service after falling below desirable performance levels Light-emitting diode (LED) traffic signal modules were first unless the owning agency has an appropriate replacement widely used in the 1990s. An LED signal module provides strategy. significant energy savings relative to an incandescent lamp, and the light source has a much longer service life. LEDs are now being implemented on a widespread basis and will see SYNTHESIS OBJECTIVE increased use as a result of the Energy Policy Act of 2005 (EPACT 2005). There are, nevertheless, concerns regarding This synthesis reports on current practices for operating, mon- monitoring, maintenance, and replacement of LED signal itoring, maintenance, and replacement of LED traffic signal modules. These concerns are centered on several factors. modules. It reviews research and documents national and It should be noted that many of the problems associated with international standards and practices pertaining to operating, LED traffic signal modules were the result of early implemen- monitoring, maintenance, and replacement of LED traffic tations. As will be discussed in more detail, the ITE standards signal modules. The synthesis includes the results of a 2006 have gone through a major revision based on early experience Institute of Transportation Engineers (ITE) survey consisting and the improvements in LED technology. The traffic signal of 75 responses from users and manufacturers of LED mod- head application of LED technology is still in a process of ules. The specific objectives of the report are continual improvements as a result of the increasing population of installed LED traffic signal modules, longer experience, · Familiarize the reader with the history of LEDs, and competition for business. · Facilitate an understanding of the issues associated with LEDs, Whereas incandescent lamps fail in a catastrophic manner, · Document lessons learned from the experiences of others, LED signal modules generally lose luminous intensity on a and gradual basis, creating uncertainty over when they should be · Present successful practices to minimize future problems. replaced. LEDs are driven by electronics, which make detect- ing failures more complex. ORGANIZATION OF REPORT Many LED signal modules were initially financed outside of The report is organized into three additional chapters plus two the transportation agency as an energy conservation incentive. appendixes. Chapter two provides an overview of current This has led to some challenges regarding replacement. Once practices. Chapter three provides examples of successful prac- installed, the cost burden for replacing LED signal modules tices. Chapter four provides conclusions and suggestions for typically lies with the transportation agency. The gradual further research. The appendixes contain the results of the two reduction of LED light output, combined with the higher costs 2006 ITE surveys, one of users and the other of vendors.