Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 8
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
OCR for page 9
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.
