Summary

The City of Portland has replaced all red and green traffic signal incandescent light bulbs with energy saving LED lights (Light Emitting Diode modules). 13,382 incandescent traffic light bulbs were replaced with LED modules, which save approximately 4.75 million kilowatt-hours per year. This is equivalent to enough energy savings to power over 350 Portland homes each year. The replacement to LED lights saves the city of Portland $335,000 annually in signal power costs.

What is it? 

There are three principle advantages to replacing municipal traffic lights with LED lights:

  1. LED modules represent an 83% to 88% percent reduction in energy consumption over standard light bulbs.
  2. LED modules are brighter and they emit light more evenly, making them more visible in foggy conditions.
  3. LED traffic lights last for 100,000 hours, compared to incandescent bulbs that last only 8,000 hours because their filaments burn out. Replacing traffic bulbs is not only expensive but inhibits traffic flow. Burned out lights are hazards, thus reducing traffic safety. LED lights avoid these scenarios all together.

How does it work?

Prior to the development of the LED modules, the City of Portland utilized incandescent light bulbs for their traffic signal indications. While these light bulbs were rated for heavier duty than the typical household light bulb, the City had to replace all light bulbs at once every two years. 'Group relamping' required a two-vehicle maintenance operation: one-bucket truck and one traffic-control pickup. The bucket truck consisted of a crewmember elevated inside a bucket to the height of the traffic signal, while the traffic-control pickup followed suit with a warning sign. Roads are not actually closed off but traffic does slow down. This process is expensive and time consuming.

In October of 2001, the City of Portland's Signal and Street Lighting Division hired an electrical contractor, E.C. Construction, to perform the LED conversion program. Installing the new LED lights requires minor modifications to the signal head to accommodate the LED modules. Because an incandescent light bulb sits within a base that is surrounded by a reflector, both the base and the reflector had to be removed for the installation of the LED module. The exterior of the signal head stays exactly the same, only the interior is altered to position the new bulb.
By February 2002, the contractor had installed 13,382 LED modules in only 4 months. Each 142-watt incandescent light bulb was replaced with a 17-watt LED module and each 59-watt incandescent light bulb was replaced with a 10-watt LED module.

The conversion project cost the City of Portland approximately $2.2 million US dollars. The project received $715,519 US dollars in energy incentive rebates from local power utilities.

The City of Portland came up with an innovative way to finance the program. Because the City's Signal and Street Lighting Division is a public agency and therefore cannot collect tax credits to help fund its programs, the Division partnered with Dooling Lease Management Corp. The private leasing company agreed to finance the program and was thus entitled to receive an Oregon State energy tax credit of $500,000. Essentially, the City of Portland leases the LED lights from Dooling Lease Management Corp. The City pays off the lease in monthly installments of $30,000. The lease will be paid off by August 2007.

Next steps

  • The current LED modules are reaching the end of their useful life, which is typically 7 years. The City anticipates replacing all traffic signals with new LED lights in the fall of 2007. The new LED modules will be more efficient than the existing LED modules, using about 75% as much power.
  • Future replacement projects will cost less because the cost for LED modules is approximately 50% less today than in 2001.
  • The City is not replacing the yellow incandescent indications because the energy savings does not cover the conversion cost. Also, because yellow indications are only activated briefly during each signal cycle, the overall savings potential is not very high.

Application

  • A city can implement this program via it's own City agency or by hiring an electrical contractor such as Portland did.
  • Innovative financing mechanisms can be applied, such as partnering with a private company that agrees to fund program.
  • The conversion program will save 'group relamping' costs and off-hour call-out costs for burn out lights because of the increased life of the LEDs.