2011

Almin Ramic, EIT

ALMIN RAMIC, EIT

5/3/2011

TRAFFIC SIGNAL LED CONVERSION STUDY

2 | P a g e

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.

3 | P a g e

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

.

4 | P a g e

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.

5 | P a g e

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

6 | P a g e

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

7 | P a g e

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.

8 | P a g e

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

9 | P a g e

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.

10 | P a g e

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

11 | P a g e

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.

12 | P a g e

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

13 | P a g e

Appendix 1: Xcel Energy Lighting Efficiency-Led traffic signal retrofit rebate Form (4)

14 | P a g e

15 | P a g e

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.