City of Yakima, Washington Department of Public Works Streets and Traffic Division

LED Traffic Signals: Saving Money and Energy

The City of Yakima, Washington has upgraded many of our traffic signals thorough out Yakima. As part of this improvement project, the signal heads have been upgraded to replace the existing red incandescent bulbs with high tech Light Emitting Diode (LED) bulbs. Additionally, the pedestrian displays are also being replaced with LED fixtures. Between 2001 and 2002, approximately 650 bulbs and pedestrian displays were upgraded to LED technology. Conversion from incandescent bulbs to LED fixtures use approximately 85% less electricity and have a significantly longer useful life.

In the 2012 the City received a grant to upgrade additional signal heads that are currently a mix of 8″ and 12″ indications to all 12″ indications, improving signal visablility. As part of this upgrade, all of the new 12″ indications will be LEDs. The City expects the work on this project to begin sometime in early 2013.

What are LEDs?

The new traffic signal bulbs use Light Emitting Diodes (LED), rather than incandescent halogen bulbs. The LEDs are small, individual electronic lights created using applied voltage to a semiconductor chip and reflector inside a small colored lens or outer casing. In contrast, the incandescent traffic bulb depends on a colored filter to produce the appropriate color. While the cost of the filter is cheap to produce, it is a very inefficient way to light the traffic signal. The red filter on a traditional incandescent signal bulb, for example, blocks 80 percent of the glow and wastes electricity.

Benefits: Cost and Power Savings

The energy saving for the LED signal is significant. The LED traffic signal bulb uses approximately 15 watts of power, compared to the average of 100 watts of power used by the traditional incandescent halogen bulb. Each traffic signal operates 24-hours per day, every day of the year. The cost to power a single 100-watt incandescent red bulb each day is about 15 cents (2.4 kilowatt hours), based on the current average of 5 cents per kilowatt hour which the City of Yakima pays. Each intersection has an average of 36 bulbs including pedestrian displays, arrows, green, yellow and red balls. The daily cost to power just the traffic signal heads is $5.40 per street intersection. Over the course of the year for 100 signalized intersections the power cost to the City of Yakima is nearly $200,000.

If all the traffic signal bulbs were converted to LED fixtures, the daily cost to power each bulb would be reduced from 15 cents to 2.5 cents. The daily cost to power the traffic signals would be reduced for each intersection from $5.40 to 90 cents. The annual cost to power the 100 signalized intersections drops from close to $200,000 to less than $35,000. Just as significantly, the total annual power use for the 100 city signalized intersections is reduced from 3,153,600 kilowatt-hours to approximately 657,000 kilowatt-hours.

Reduced Maintenance of LEDs

LED bulbs are brighter than incandescent bulbs and last an average of ten years compared to one year, common for incandescent bulbs. Currently, the red bulbs in each traffic signal are replaced each year, requiring the trucks and manpower to replace the bulbs which also ties up traffic. The LEDs are virtually maintenance free, eliminating annual re-lamping costs.

Initial Costs and Rebates

The LED conversion program required an initial cost to purchase the LED fixtures. The average cost of the LED red bulb is $85, compared to $3 for incandescent fixtures. However, over the 10 year life of the LED, the City of Yakima would otherwise spend $30 in replacement bulbs. Re-lamping staff/equipment costs average $50 per signal head. The LED fixture would cost $50 to install compared to $500 for annual re-lamping costs over a decade with incandescent bulbs. The $125 installed price for each LED compares very favorably to the $530 cost of annual re-lamping with incandescent bulbs.

Nationwide, power companies have been very supportive of the LED traffic signal conversions. Currently the City of Yakima is working with Pacific Power to receive a rebate for each LED installed. The existing rebate is $40 for each red ball, $50 for each LED “Don’t Walk” and $20 for each LED “Walk”. In 2001, the City of Yakima received a rebate check of $5,063 from Pacific Power. Additionally, a rebate of approximately $21,000 is expected in 2002 due to the CBD signal project. Chris Kanoff, Project Manager for Energy Services of Pacific Power and Light has worked closely with City staff to administer the rebate program and expressed strong support for the program.

A total of 650 LED fixtures were installed between 2001 – 2002, in conjunction with the CBD project. The cost to power the 650 LED bulbs for one year is approximately $6,000 compared to $35,600 to power 650 incandescent bulbs. The Streets and Traffic Division purchased additional LED fixtures with the rebate funds to continue the program.