Lighting

Chicago, USA

LED traffic lights reduce energy use in Chicago by 85%

Summary

This program has delivered immediate and sustained reductions in the city’s emissions. LED traffic lights use almost 85% less energy. As a result the city is saving $2.55 million annually in energy savings and $100,000 annually in materials. It is also reducing 23,000 CO2 tonnes annually.

What is it?

A City run project (coordinated by two Departments: Streets and Sanitation and General Services) retrofitting and installing Light-Emitting Diode (LED) energy efficient lighting in all of the City’s traffic lights at 2,900 intersections. So far 1,000 have been installed; the project will take another three years to complete.

Funding

Initial funding was helped by a settlement agreement between the City and Commonwealth Edison (ComEd) - one of the nation’s largest electric utilities. The settlement money ($100 million) was paid following litigation over the Franchise Agreement between the City and ComEd. $2 million of this money was used to fund the project - $1million as a start up. When completed the project will cost $32 million US – most of this is City bond money.

How does it work?

The City started the project in 2004 as part of its aggressive energy efficiency targets for the city and agency buildings to reduce its environmental footprint by 30% by 2020. The LED program makes up 15% of this target.

The project started with funding grants and settlement money but is now funded through City bonds – these bonds will be paid back through energy savings over 6 or 7 years.

LED traffic lights are more efficient and durable - retrofitting and installation is a highly successful and easily applied program for cities. There are three principle advantages to upgrading municipal traffic lights to LEDs:

• LEDs are brighter - emitting light more evenly, making them more visible in foggy conditions.
• LED traffic lights last for 100,000 hours, compared to incandescent bulbs, which have filaments that burn out and may last only 8,000 hours before needing to be replaced.
• Replacing bulbs costs money and the replacement process inhibits traffic flow. Fewer burned-out lights also increase the safety of intersections.

Benefits of switching to LEDs include the ability to use backup power supply for traffic signals during power cuts. As a result Chicago installed PowerBack ITS Systems at 800 intersections – some retrofitted, some new.

• The PowerBack ITS System is a complete battery backup system for traffic signal intersections.
• It operates traffic signals after a power cut for up to 24 hours.
• They can be used in traditional incandescent traffic signal systems – but provide a much longer range of emergency coverage with more energy efficient LEDs.

Next steps

Looking at new LED technologies and other technologies for street lighting for streetlights. Traffic lights use 6 megawatts of power while streetlights 70 mega watts.

Application

• Typical incandescent traffic lights use 100-watt or 150-watt bulbs that are operating 24 hours a day, utilizing more than 2.4 kilowatt-hours per day.
• At 8 cents per kilowatt-hour, one intersection can cost almost $600 per year in electricity. Large cities with thousands of intersections spend millions of dollars on electricity just for the consumption of traffic lights (Chicago alone spends $3 million annually).
• LED arrays consume 12-20 watts instead of 100, reducing overall energy consumption considerably.
• Solar panels can power LED traffic lights in remote areas, reducing the costs associated with installing power lines.
• Another benefit of LED traffic signals is the fact that they do not burn out all at once - when an incandescent filament burns out, the entire light ceases to function, in LEDs, a single diode or a cluster of diodes can stop working or burn out, but all the other diodes operating independently will continue to function normally. This feature eliminates the safety risks and traffic congestion problems associated with burnt-out traffic signals.
• Traffic flow management consists of set light timing, activated traffic signals, signal synchronization and more techniques that work to improve traffic flow. With these programs commuters should experience a reduction in travel time, less gas consumption and cost savings due to the coordination of signals. Environmentally, these strategies will result in reduced air pollution and GHG emissions from idling.
• It is now possible to purchase LED in all three colors needed for traffic signals.