Lighting

Portland, United States of America

Portland replaces 1,000 traffic intersection signals with LED lights, saving millions of kilowatt-hours per year.

What is it?

Portland has reduced energy consumption, fuel consumption and greenhouse gas emissions by first retrofitting and then re-timing traffic signals. LED lights were introduced to all intersections in the city, saving approximately 4.75 million kilowatt hours per year, the equivalent of annual energy consumption in 350 homes and equivalent to 2,880 tCO2. Re-timing of signals at 135 intersections on 16 major streets has resulted in less idling time, saving motorists over 1,750,000 gallons of fuel each year – a further 15,460 tCO2 reduction.

How does it work?

LED modules reduce energy consumption by 83-88% compared to standard light bulbs; moreover they are brighter, more effective and last 10-15 times longer than incandescent bulbs. Replacing traffic bulbs with LEDs reduces maintenance costs and accidents. Portland took the decision in 2001 to convert to LED lighting; within four months, the contractor had installed 13,382 LED modules at a cost of $2.2 million.

The project received $715,519 in rebates from local energy utilities and the city developed an innovative financial program, making use of state tax credits, to lease the installations until they have been repaid – using the savings from the LEDs.

Traffic signal optimization is the process of changing the timing parameters relative to the length of the green light for each traffic movement and the timed relationship between signalized intersections. Optimizing traffic signal timing reduces both idling and the acceleration of vehicles, leading to less fuel consumption and less emissions.

As traffic patterns change throughout the day and the week, it is appropriate to modify the signal timing parameters to reflect the needs of these unique traffic patterns. Traffic engineers perform the optimization process, either as employees of the municipality or as employees of a consulting engineering firm, using software programs – for example, Portland uses Trafficware’s Synchro Studio program. (More information can be found at: http://www.trafficware.com/products.html)

The cost to re-time one intersection ranges from $1,000 to $3,000 per intersection. The cost of the signal optimization work was $533,000, which was provided by the Climate Trust of Oregon. Due to budget constraints, the City of Portland would not have been able to do this work without funding from The Climate Trust.

Next steps

• New LED installations will be more efficient than the existing modules, meaning the city will continue to make savings and reduce emissions. Moreover, replacements will cost less as the price of LED technology is falling.
• The city intends to re-time more signals. For every 1000 gallons of fuel avoided, 8.8 metric tons of CO2 are saved!

Application

• A city can implement an LED program via its own City agency or by hiring an electrical contractor. 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.
• Optimizing traffic signal timing is a fairly straightforward process. Agencies operating traffic signals can either having their traffic engineering staff perform the retiming process or they can hire a traffic-engineering consultant.
• A computer software program is required that models existing signal operations and recommends improved signal timings.

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