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9 CHAPTER THREE SUCCESSFUL PRACTICES The development of successful practices has many complexi- over. In years 2012 to 2016, $250,000 will be needed in the ties owing to the differences in how agencies operate and main- RCOC budget. tain their traffic signals. Further, while experience is building, LED traffic signal modules are an evolving product. The fol- This plan will allow three things to occur: lowing contains insights developed from several agencies. 1. A mostly uniform and known budget amount will be established. ROAD COMMISSION OF OAKLAND COUNTY, 2. The budget amount will not be increased over what has MICHIGAN, CASE STUDY been established over the last few years. The Road Commission of Oakland County (RCOC), Michigan, 3. In several years, a large number of LEDs were installed. began installing LEDs in 2000. The total number of intersec- This schedule allows for a smoothing of the replace- tions maintained is 1,300, with 680 on LEDs. The LEDs are ments so no year will see a big budget increase. projected to last between 5 and 10 years (LEDs last longer in cooler climates). RCOC in 2006 received lab tests back Essentially, by looking a few years out and developing a on sample LEDs installed in 2000. These tests showed that plan that allows more consistent funding, the RCOC has 10 years is a reasonable life span for LEDs. Therefore, RCOC developed a strategy that puts them on what is essentially a expects that their LEDs will last from 8 to 10 years. 10-year replacement cycle. However, it should be noted this is not based on wishful thinking, but on evaluation of what Given the above results and the existing age of RCOC they expect will be the performance of their LEDs based on LEDs, the following schedule for LED replacing has been manufacturers' specifications and known degradation curves. undertaken. ASPECTS OF SUCCESSFUL PRACTICES Replacement of First Wave of LEDs Synthesis study efforts revealed that there are several aspects · Year 2008--Replace 36 locations installed in 2000 and to successful LED traffic signal module practices including 2001 at a cost of $150,000. purchasing, monitoring, maintaining, and replacing LED · Year 2009 to 2016--Replace about 81 per year at a cost modules. Each of these issues is interrelated and cannot be of $350,000 per year. considered in isolation. Understanding successful practices is an evolving science and users of LEDs should continue to monitor industry practices. Purchase specifications should On-Going Replacement Schedule also consider requesting degradation information from man- ufacturers under varying operating conditions. · Years 2017 and beyond--Start replacing 10% per year, estimated to be about 95 and ramp up to 200 by year There is clearly a need for an LED replacement schedule 2026 when all signal heads will use LED modules. This that routinely replaces a portion of the LED signal modules replacement schedule will provide for incremental every year so that agencies are not placed in a position of upgrades from incandescent to LEDs as well as for the infrequent, but expensive, replacement programs that tend to addition of new signal installations. postpone replacement of LEDs that have passed their useful life. This problem is likely to be most challenging in agencies Table 2 shows the estimated funding that is recom- that replaced their incandescent lamps all at one time. mended to meet this schedule. This schedule assumes that in years 2006 and 2007 the $200,000 in the budget will not be Purchasing, as a minimum, LEDs compliant with ITE used to install new LEDs, but will instead be rolled over to specifications will address a number of issues associated with provide future funding for replacement. Also, in years 2008 early LED implementations. When making large purchases, to 2010 (assuming a continued $200,000 budgeted), the it may be desirable for a sample of the product to be sent out remaining monies not used to replace LEDs will be rolled for conformance testing. It would also be desirable to test in
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10 TABLE 2 cleaning will assist in determining if lens cleaning is a cost- RCOC REPLACEMENT STRATEGY effective strategy to increase service life. This would require a program where samples of modules (cleaned and not cleaned) Year LED Repl. RCOC Local RCOC Roll-Over Cost Cost Cost Budget Monies were sent for laboratory testing. 2006 $200,000 $200,000 The replacement strategy for LEDs is the most complex 2007 $200,000 $400,000 and currently least understood aspect of LEDs. While the early 2008 $150,000 $135,000 $15,000 $200,000 $450,000 2009 $350,000 $325,000 $25,000 $200,000 $300,000 generations of LEDs are reaching their useful life, they do 2010 $350,000 $300,000 $50,000 $200,000 $150,000 not represent current technology and are at best only an indi- 2011 $350,000 $275,000 $75,000 $200,000 $0 cator of what may be experienced with newer technology and 2012 $350,000 $250,000 $100,000 $250,000 2013 $350,000 $250,000 $100,000 $250,000 designs. Agencies will have to be proactive if they are to 2014 $350,000 $250,000 $100,000 $250,000 avoid being driven to costly reactive maintenance. 2015 $350,000 $250,000 $100,000 $250,000 2016 $350,000 $250,000 $100,000 $250,000 The simplest form of replacement strategy would be to begin by not doing a systemwide replacement program. The the shop the LEDs with the specific brands of load switches most conservative and potentially most costly approach is to and MMUs and/or CMs being used by the agency. have a maintenance program based on the LED warranty period. Assuming a 5-year warranty, 20% of the traffic signal Monitoring the maintenance experience with LEDs and modules would be replaced each year. This would allow an keeping records will assist the agency in identifying trends and initial establishment of a worse-case budget. At the end of developing a proactive approach to replacement. While the life 5 years, an experience base of failures at 1 through 5 years of LEDs is long compared to incandescent lamps, LEDs are would be established. At the end of 5 years, the budgeting more susceptible to variations in the environment (heat and process would be established that would allow for the com- cold) than are incandescent lamps. This is another reason for plete replacement of 5-year-old LEDs. However, at this point, developing a maintenance history of LEDs including the color laboratory testing could be undertaken to determine the light and type (circular or arrow) of the display, make and model, output (before and after cleaning) for a representative sample date of manufacture, date of installation, and the type of opera- of LEDs in different operating environments. tion. Yellow indications have shorter duty cycles than reds and greens. Likewise, some reds and greens may have long duty Based on the results of testing, a revised maintenance sched- cycles due to the traffic patterns. A rural traffic signal may have ule could be developed. It would be speculative to suggest long green times on the arterial and long red times on the cross what adjustment should be made, but consideration should street. Failure to understand these varying conditions could lead be given to the fact that LEDs are different from incandescent to erroneous conclusions with regard to LED module life. lamps. It might be desirable to experiment with different strategies that reflect the duty cycle, operating environment, Maintenance intervals are naturally going to increase and relative importance of the indication. Reds might be because of the longer life of LEDs. This reduced maintenance replaced where duty cycles are high and yellows and greens interval is likely to lead to a lack of cleaning of the LEDs. This cleaned if testing showed the approach to be cost-effective. lack of cleaning will lead to a maintenance depreciation of Therefore, until an adequate history is developed, careful the light output in addition to the normal degradation owing experimentation may be a cost-effective strategy to not pre- to usage and age. To determine if intermediate cleaning is nec- maturely replace LEDs that have additional useful service essary, a systematic monitoring program, as previously men- life. However, just waiting until the LEDs can no longer be tioned, is essential. Testing of light output with and without seen is not a recommended strategy.