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