energy & emissions
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Newer, energy-efficient traffic signals are made up of many small LED bulbs, each the size of a pencil eraser. They are used together in an array to create a brighter, more evenly-distributed light compared to the individual halogen bulbs used in conventional signals.
LED Traffic Lights
The City of Denver has one of the largest light-emitting diode traffic light inventories in the country.
In the late 1990s, the city's Traffic Operations Division began an ongoing retrofit program to convert its traffic signals from incandescent lamps to LED bulbs. Since then, more than 48,000 red, yellow and green traffic and pedestrian signals have been converted to LED, which saves the city more than $800,000 per year in energy, labor and material costs.
Denver has approximately 1,250 traffic intersections containing over 55,000 signal indicators, and they must be powered 24 hours a day.
A single four-way conventional traffic light with incandescent lamps consumes roughly 85 kilowatts of electricity per day and costs about $1,600 per year to operate. For a city the size of Denver, traffic lights would consume 931 million kilowatts of electricity per year at an annual cost of $2 million.
LED traffic signals, on the other hand, use 90 percent less energy and last up to five times longer. In addition to the tremendous energy savings, their low-maintenance performance means that technicians are dispatched for fewer repairs, which helps lower liability costs and simplify parts inventories. The city's LED conversion has reduced annual emissions of carbon dioxide by 2,937 tons. This is equivalent to removing 374 cars from the road.
At the launch of the program, city experts worked directly with manufacturers to develop and refine traffic light LED technology, improving aspects such as signal visibility, bulb life, energy efficiency, and reduced maintenance. The traffic light retrofit program received a national award from the U.S. EPA's Green Lights program for energy conservation.
IN-DEPTH:
- Visit the Web site for Denver's Traffic Engineering Services.
- Learn more about how LEDs work.
