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