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11 SUMMARY OF FINDINGS Light-emitting diodes (LEDs) are widely used and becoming more so as the result of the Energy Policy Act of 2005. The quality of the product has been steadily improving and the ITE 2005 LED specification addresses many of the early prob- lems experienced by first adopters of LEDs. Users of LEDs appear to be largely satisfied with the performance of LEDs. Nevertheless, there are some concerns that have not been totally addressed. Issues remaining to be addressed include the following: ⢠Definition of a sustainable LED replacement strategy: â Determining appropriate replacement schedule, â Determining funding for replacements. ⢠Need for improvement of technical standards: â Better failure detection, â Harmonization with related standards, â Ability to further reduce energy consumption. The life of LEDs from an economic, performance, and safety point of view is not well understood. This is natural given LEDs are a new and improving technology. However, the uncertainty associated with these issues is a major imped- iment to development of a sustainable replacement strategy. LEDs are operating in an environment developed for incan- descent lamps. This has led to LEDs being designed to âworkâ in a world defined by Thomas Edison in the 19th century. Resolving these issues is difficult because of the installed base of existing equipment and the lack of a clear path to specification of a new âsystemâ to deliver traffic signal dis- plays safely and efficiently. CONCLUSIONS LEDs are the likely de facto technology for traffic signal dis- plays for the foreseeable future. They are generally meeting the needs previously met by incandescent lamps at greatly reduced energy consumption and reduced life-cycle cost. LEDs have a number of positive benefits including increased life that reduces the exposure of maintenance personnel to working in the roadway. However, a number of technical issues have not been completely addressed. The next section contains suggestions for further research to address current limitations in understanding and legacy issues emanating from standards developed for incandescent lamps. SUGGESTIONS FOR FURTHER RESEARCH Based on the results from this synthesis work, the most press- ing LED need is to address the fundamental issue of a dark display not being sensed by the conflict monitor or malfunc- tion management unit. This is a complex issue that includes both the harmonization of related standards and the funda- mental issue that an LED display is not electrically the same as an incandescent lamp. This issue would best be addressed in a systematic manner involving the standards organizations (National Electrical Manufacturers Association and ITE) as well as the vendors. While this issue does not seriously affect current day-to-day operations, it does potentially impact future liabilities. The issue also limits the ability of LEDs to be more energy efficient in the future. The issue of LED module life and LED module degradation also warrants national attention, but would be best done at the regional level, primarily because it is impractical for most individual agencies to undertake the research necessary to determine the most cost-effective maintenance strategy and because performance is affected by the operating environment. Future research would include development of a better under- standing of LED module life by color under differing operation conditions including duty cycle and operating environment. Additional research would also include the development of suggested practices for monitoring and maintaining LED mod- ules so that understanding of performance could be refined over time as LED modules continue to evolve. CHAPTER FOUR CONCLUSIONS
