2011
Almin Ramic, EIT
ALMIN RAMIC, EIT
5/3/2011
TRAFFIC SIGNAL LED CONVERSION STUDY
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In 2003, the City of Minnetonka replaced 75% of its red and about 50% of its green
incandescent traffic signal lights with new signal lights featuring highly efficient light-emitting
diodes (LEDs). The right timing and carefully arranged financing resulted in a successful energy-
efficiency project, with energy and maintenance savings and fast net payback for the project. At
the time, yellow and green LEDs were less efficient and much more expensive then red, so the
city opted for replacing mostly red and pedestrian lights. Traffic signals that use LEDs consume
up to 90 percent less energy and generally last 7-10 years, compared to just a year for a
incandescent light signal.
In the signal survey which was completed in the April of 2011 in the City of Minnetonka
it was determined that most of the LED traffic signals that were installed in 2003 are still fully
operational. Only 10% of all LED green traffic lights, and 1% of red, pedestrian and arrow
signals are in condition for replacement. Most of these are still operational, but have a number of
diodes burned out. Moving away from incandescent to LED traffic lights will not only save
energy, but will allow moving from reactive, emergency maintenance and developing a plan for
preventative maintenance.
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Table of Contents Introduction ................................................................................................................................. 4
Typical Power Ratings ................................................................................................................ 5
Survey Results ............................................................................................................................. 6
Energy and Cost Savings ............................................................................................................. 7
Improved Safety .......................................................................................................................... 9
Preventative Maintenance vs. Reactive Maintenance Plan ...................................................... 10
Material and Installation Costs Estimate: .................................................................................. 11
Recommendations ..................................................................................................................... 12
Appendix 1: Xcel Energy Lighting Efficiency-Led traffic signal retrofit rebate Form (4)
....... 13
Bibliography .............................................................................................................................. 15
.
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Introduction
Light Emitting Diode (LED) lights are more efficient option for traffic signal lights than
traditional incandescent bulbs (STD). The key advantages of having LED signals are
Low power consumption 4 W to 12.5W,
Life span of approximately 7 to 10 years,
The elimination of catastrophic failures, and
The elimination of phantom illumination.
A typical incandescent bulb that is used for traffic signals is between 135 and 150 Watts.
In the current economy, where prices of gas and coal are rising, the cost of electricity is going
up. Energy savings resulting from the usage of LED signals can be as high as 90%. LED traffic
signals also offer significant peak demand savings since they operate 24 hours a day. In addition
to the low energy usage, the long life of LED signals means low maintenance costs, which makes
LED signals a worthwhile investment while at the same time being environmentally friendly.
Another very important benefit of LED signals is the elimination of catastrophic failures. Unlike
an incandescent bulb which has only one filament, an LED signal is made out of a matrix of
several dozen LEDs. The signal continues to function even if several of these miniature diodes
stop working. Catastrophic failures in LED’s are very rare, and mostly caused by abrupt surge of
power. On the other hand, when the filament of an incandescent bulb fails, the display goes dark
requiring immediate replacement. This characteristic of LED lights will allow for the move from
reactive maintenance to plan driven preventative maintenance. Preventive maintenance plan is a
schedule of maintenance actions aimed at the prevention of breakdowns and failures. The
primary goal of preventive maintenance is to prevent the failure of equipment before it actually
occurs.
LED signal lights are brighter than an incandescent traffic signal. This characteristic
improves intersection safety because is eliminates phantom illumination. During morning and
evening hours on signals east-west approaches, all colors seem to light up when the sunrays fall
directly on these signals. This problem is eliminated when LED signals are used because in they
do not use reflectors like in Incandescent traffic signal bulbs to increase the lights brightness.
There is only one downside to the LED lights and that is their initial cost. It can range from
$100.00 for a 12”red light, $127.00 for a pedestrian display, to $170 for 12” green light
depending on the type, quality and the manufacturer. Some lower quality LEDs can be purchased
cheaper than shown in this study. Compare this to typical incandescent traffic signal bulb costs
of about $2.75 per bulb. Still, in most of the cases this initial cost is made up by the savings in
energy cost in less than 5 years.
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Typical Power Ratings
LED signals require very low power to operate. The typical power consumption ranges
anywhere from 4 to 22 watts, depending on type of LED light, number and color of diodes. The
Table1 and Chart 1 illustrate the power usages for incandescent bulbs and LED signals obtained
from Act One Communications Inc.
Display Type Typical Power (Watts)
Incandescent Bulb (Standard-STD) 135
Pedestrian Incandescent 60
12" Red LED 7.5
8" Red LED 4
12" Red Arrow LED 7
12 " Yellow LED 10
8 " Yellow LED 8
12 " Yellow Arrow LED 8
12 " Green LED 12.5
8" Green LED 5
12" Green Arrow LED 9
Pedestrian LED 6
Table 1: Typical Power Usage of LED and Incandescent Bulbs in Traffic Signals
Chart1: Typical Power Usage of LED and Incandescent Bulbs in Traffic Signals
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Survey Results
The survey of traffic signals done in April of 2011 in the City of Minnetonka produced
these findings. In Table 2 are presented surveyed totals of the types of the light bulbs used for
specific type and size of traffic lights.
9" WALK 9" DON'T
WALK
12" WALK 12" DON'T
WALK
12" WALK/DON'T
COMBINED LED STD LED STD LED STD LED STD LED STD
48 24 48 24 103 49 101 51 123 18
Table 2: Current number and types of traffic lights in the City of Minnetonka
The current situation in the City of Minnetonka traffic signals is shown in Table 3, where
at the signalized intersections 44% of signals for vehicular traffic, and 72% for pedestrian traffic
was replaced to LED lights.
Number of Lights Percentages
TOTAL LED SIGNAL LIGHTS 1185 44%
TOTAL STD SIGNAL LIGHTS 1506 56%
TOTAL LED PED SIGNAL LIGHTS 423 72%
TOTAL STD PED SIGNAL LIGHTS 166 28%
Table 3: Current totals of LED and STD lights in the City of Minnetonka
Type Of Signal Light Signal Lights City is
responsible for re-lamping
Signal Lights City is
responsible for energy cost
% of Total % By
Type
% of
Total
% By
Type
LED R,Y,G and Arrow 761 40.31% 48% 1185 36.13% 44%
LED PED Walk/DW 253 13.40% 84% 423 12.90% 72%
INCONDESCENT R,Y,G and Arrow 826 43.75% 52% 1506 45.91% 56%
INCONDESCENT PED Walk/DW 48 2.54% 16% 166 5.06% 28%
TOTAL R,Y,G and Arrow 1587 2691
TOTAL PED Walk/DW 301 589
Table 3a: Current totals of LED and STD lights in the City of Minnetonka by city duty
12" SOLID 8" SOLID 12" ARROW
RED YELLOW GREEN RED YELLOW GREEN RED YELLOW GREEN LED STD LED STD LED STD LED STD LED STD LED STD LED STD LED STD LED STD
513 169 129 504 311 313 5 0 0 22 0 22 124 25 45 214 58 237
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Energy and Cost Savings
As a part of the study, two intersections were looked at. One mostly retrofitted with LED
signals and other with all of the lights incandescent. The intersections studied were Co Rd No.
101 and Co Rd No. 5 and Co Rd No. 62 and Woodland Road. The types of light bulbs that each
intersection has are show in the Tables 4 and 5. Their energy usage was monitored and
compared.
INTERSECTION 1 12" SOLID 12" ARROW 12"
WALK/DON'T
COMBINED
Signal LOCATION RED YELLOW GREEN YELLOW GREEN
LED LED LED INC INC LED
Co Rd No. 101 and Co Rd No.
5 (Minnetonka Boulevard)
4 4 4 2 2 2
Co Rd No. 101 and Co Rd No.
5 (Minnetonka Boulevard)
4 4 4 2 2 2
Co Rd No. 101 and Co Rd No.
5 (Minnetonka Boulevard)
4 4 4 2 2 2
Co Rd No. 101 and Co Rd No.
5 (Minnetonka Boulevard)
4 4 4 2 2 2
Table 4: Number and Types of lights at Intersection of Co Rd No. 101 and Co Rd No. 5
INTERSECTION
2
12" SOLID 12" ARROW 12"
WALK
12"
DON'T
WALK
Signal
LOCATION
RED YELLOW GREEN RED YELLOW GREEN
INC INC INC INC INC INC INC INC
Co Rd No. 62 and
Woodland Road
2 2 2 1 1 1 2 2
Co Rd No. 62 and
Woodland Road
2 2 2 1 1 1 2 2
Co Rd No. 62 and
Woodland Road
4 4 4 1 1 1 2 2
Co Rd No. 62 and
Woodland Road
4 4 4 1 1 1 2 2
Table 5: Number and Types of lights at Intersection Co Rd No. 62 and Woodland Road
Based on actual meter readings over a period of one month, the power consumption of
the two intersections was compared. Intersection 1 retrofitted with LEDs and Intersection 2 with
standard incandescent lights. The total power consumption was 252 kWh for CR-101 and CR-5,
and 1790kWh for CR-62 and Woodland Rd. As can be seen in the Table 4 at Intersection 1,
there are 16 incandescent bulbs used for yellow and green arrows, the total number of 12” solid
lights is larger by 16, and the number of 12” arrow lights is greater by 4 than at Intersection 2.
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Based on the gathered data, number and types of lights, Table 6 shows the estimates for
current and predicted hourly power consumption for all of the signalized intersections in the
City.
Table 6: Estimate for current and predicted power consumption in the City of Minnetonka
Based on the above estimate for hourly consumption, the LED signals consume about
90% less energy than conventional signals with incandescent bulbs. For the 64 intersections that
the city is paying for power consumption we can calculate current annual power consumption for
the two different types of signal lights and predicted consumption after all of the signals were
retrofitted to LED lights.
Table 7: Estimate for Annual Energy Consumption and Energy Cost
Based on the above averages, the LED signals consume about 90% less energy than
conventional signals with incandescent bulbs (1)
. For the 64 intersections in the city, the annual
power consumption for the two different types of signals is shown in the Table7.
If all of the 64 intersections in the city were fully converted to have LED signal lights, the
average energy savings would be about 855,000 kWh per year, or almost $70,000 with current
price of electricity.
Display Type Minnetonka Power Usage
(kWh)
Predicted Power Usage If
Switched to LED (kWh)
Incandescent Bulb 203.31 0.00
Pedestrian Incandescent 9.96 0.00
12" Red LED 3.85 5.12
8" Red LED 0.02 0.02
12" Red Arrow LED 0.87 1.04
12 " Yellow LED 1.29 6.33
8 " Yellow LED 0.00 0.18
12 " Yellow Arrow LED 0.36 2.07
12 " Green LED 3.89 7.80
8" Green LED 0.00 0.11
12" Green Arrow LED 0.52 2.66
Pedestrian LED 2.54 3.53
TOTAL 226.60 kWh 28.86 kWh
Current
Annual
Consumption
kWh
Current
Energy Costs
Predicted
Annual
Consumption
kWh
Predicted Energy
Cost
Incandescent Power
Consumption
921,326 $73,838 0
0
LED Power Consumption 57,599 $4,616 124,654 $9,990
TOTALS 978,925 $78,454 124,654 $9,990
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Improved Safety
LED signals eliminate catastrophic failures of signals. LED signal is a matrix of large
number of individual diodes and a chance of all of them failing at exactly the same point in time
is very rare. The signal continues to function even if multiple miniature diodes have stopped
working (see Pictures 1,2,3). This is not a case with incandescent bulbs. When incandescent Bulb
filament fails, it requires immediate replacement.
Picture 1: Failing LED Signals at Ridgedale Drive and Hwy394 west bound ramp,
Minnetonka,MN
LED signals are brighter when compared to incandescent traffic signals. Brightness of the
light enhances intersections safety especially for signals on east‐west approaches during morning
and evening hours. If the sunrays falls directly on the non LED signal all colors seem to light up.
This event is known as the phantom illumination. The sun’s light then reflects off the surface of
the lamps, possibly giving the false impression that the lamp is on. Example of this is obvious in
the sunny morning hours going west of Minnetonka Ave, at the intersection with McGinty Rd.
The task of the driver is then to determine which of the three color lamps is actually illuminated.
The LED signals have a great advantage because its lens reflects much less of the sun’s light
back at the observer then the Incandescent traffic signals.
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Preventative Maintenance vs. Reactive Maintenance Plan
Preventative and Reactive maintenance efforts and costs can be related to the quality of
design practices, construction methods, and the use of quality parts. Effective preventative
maintenance practices can decrease the cost of operating and maintaining a traffic signal
infrastructure (3)
- resulting in safe and reliable intersections. Preventive maintenance (PM)
considers a schedule of maintenance actions aimed at the prevention of breakdowns and failures
by replacement of equipment before it actually occurs. Preventive maintenance activities include
inspections of equipment,
keeping condition of equipment data, and
partial or complete overhauls at specified periods.
In addition during inspections, maintenance workers can record equipment deterioration
in order to replace or repair worn parts before they cause system failure. Gather data will also
help continuous development of PM plan. The ideal PM program would prevent all equipment
failures before they occur with reactive maintenance only performed on a hierarchical priority
basis considering the seriousness of reported problems.
In the City of Minnetonka traffic signal maintenance plan, a large part of the maintenance
work would be inspecting traffic control equipment, but the main element is replacing parts
before they fail. This replacement program would be scheduled with consultation of LED lights
manufacturers’ specification about the lights life expectance. The reactive maintenance would be
only performed on an on call/as needed basis. As the replacement program moves forward, the
number of hours spent in a reactive maintenance should considerably decrease.
The PM includes:
Semi-annual inspections and testing of control equipment, intersection hardware,
vehicle detector loops, pedestrian pushbuttons, poles, signs, signal heads, and
mounting hardware(3)
;
Annual cleaning of all signal lenses;
Planned re-lamping cycle of 8-10 years of all LED Red, Yellow, Green, Don’t
Walk, RGY arrows, and countdown timers; and
Reactive re-lamping of failed LED and non/LED light bulbs
Long-term benefits of preventive maintenance include:
Improved system reliability;
Decreased cost of replacement;
Decreased system downtime; and
Better spare parts inventory management.
Implementation may start with initial reliability training in PM and inspection monitoring.
The goal of inspections is to achieve a condition monitoring and preventive maintenance
program that is
Documented
Executed
Tracked
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Material and Installation Costs Estimate:
Material LED Incandescent Bulb
12"(Red) $100.00 $2.75 /bulb
12"(Red Arrow) $114.00
8"(Red) $114.00
12"(Yellow) $110.00
12"(Yellow Arrow) $114.00
8"(Yellow) $115.00
12"(Green) $170.00
12"(Green Arrow) $157.00
8"(Green) $130.00
Pedestrian Separated $127.00
Pedestrian Joined $127.00
Labor (per retrofit installation) $55.00 $55.00
Table 8: Estimate for Material and Labor cost per light
(Prices were obtained from Act One Communications Inc.)(2)
COST
MATERIAL
LABOR TOTAL COST
Cost to replace ALL to LED $400,000 $180,000 $580,000
Cost to retrofit all non-LED to
LED
$210,000 $90,000 $300,000
Table 9: Total Estimate for Retrofitting
Above numbers only take into consideration savings in energy cost. The savings in change of
maintenance approach and safety improvement should also be considered. Another thing that has
to be considered is that the cities energy company Xcel energy has the Lighting Efficiency-Led
traffic signal retrofit rebate program (see Appendix 1). This rebate program could cover up to
between $10,000 and $25,000 of project cost, depending on the number of lights retrofitted. This
is something that could play a very important role with the retrofit planning schedule.
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Recommendations
LED traffic lights are steadily replacing the original traffic lights because they are more
efficient than the incandescent bulbs. When traffic signal lights fail, it causes lots of confusion
among drivers, accidents occur and lives are endangered. Due to the many operational
advantages, lower energy consumption, and safety, the benefits of LED signals outweigh the
initial investment.
The City of Minnetonka should retrofit all the traffic signals to LED signals and require
all new traffic signal installations to be LED. The net payback should be very fast. Based on the
performance of LED signals that have been installed in 2003 the life of the LED lights in these
types if conditions is more than 8 years. The benefits in energy savings, maintenance and safety
largely outweigh the initial investment. The City should develop the plan to replace all of the
traffic signal lights, including the ones installed in 2003 over the next 5 years. This would mean
retrofitting about 13 intersections per year. This approach would allow for easier transition from
emergency to preventative maintenance.
The best cost/benefit ratio is received by first replacing all of the non-LED lights that the
City is paying the electricity for. By doing this, the City could seek a partnership from the
Hennepin County, because they are responsible for re-lamping 30 out of 64 intersections. This
approach would need less funding, had faster implementation (1-2 years), but the transition from
emergency to preventative maintenance would be longer. This option would require more
frequent inspection to prevent outages of the older previously installed LEDs. Keeping the good
records on replaced traffic signals is detrimental to development of extended preventative
maintenance plan.
Another benefit that could play an important role in deciding to invest in the retrofits is
the Xcel energy rebate program (see Appendix1). This program is currently available, and could
allow for up to $25,000 rebate after retrofits are implemented. If there is a chance to retrieve
some of the total project cost for replacing non-LED to LED, the City may consider additional
retrofits of traffic lights each year.
Table 10: Summary of Cost and Savings for Retrofitting
Replace &
Retrofit
to LED
COST OF
MATERIAL
COST
OF
LABOR
TOTAL
COST
Cost/ year
based on 5-
year plan
SAVINGS
in
Energy/year
Total
XCEL
REBATE
All the lights the
City is paying
electricity for
$ 290,000
$
180,000
$ 470,00
$ 94,000
$ 70,000
$ 25,000
Only non-LED
lights the City is
paying electricity
for
$ 210,000
$ 90,000
$ 300,000
$ 60,000
$ 70,000
$ 25,000
All the lights the
City is responsible
to re-lamp
$175,000
$105,000
$280,000
$55,000
$37,000
$10,000
Only non-LED
lights the City is
responsible to re-
lamp
$107,000
$48,000
$155,000
$31,000
$37,000
$10,000
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Appendix 1: Xcel Energy Lighting Efficiency-Led traffic signal retrofit rebate Form (4)
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Bibliography
(1) United States. TED, Department of Public Works, City of Little Rock “Conventional
Vs LED Traffic Signals” http://www.cee1.org/gov/led/little_rock.pdf , July 1, 2003.
April 2011.
(2) Act One Communications Inc. http://www.actone1.com/Traffic/signals.htm
May 1st, 2002. April 2011
(3) United States. City of Richmond, CA “Traffic Signal Maintenance”
http://www.richmond.ca/services/ttp/signals/maintain.htm 2011.April2011.
(4) Xcel Energy, Minnesota. “Lighting Efficiency- Led traffic signal retrofit rebate” http://www.xcelenergy.com/staticfiles/xe/Marketing/MN-Bus-Lighting-LED-Traffic-
Signal-Retrofit-Rebate-2010.pdf 2010. April 2011.
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