Light Emitting Diode Technology...
Even Traffic Lights Can Save Energy...and Tax Dollars

Light-Emitting Diode, or LED, traffic signals can be real energy and dollar savers.
LED traffic light
Here’s the low-down on potential energy savings, technical performance, market applications, availability, cost effectiveness, their relationship/adaptability to codes.

According to ENERGY STAR's Traffic Signals website, LED traffic signals have a “significant energy savings potential,” possibly saving “...2.7 billion kilowatthours a year nationwide.”

LED traffic signals have several advantages over traditional incandescent type of traffic signals. LED signals enjoy a lifespan ten times longer, resulting in lower maintenance and replacement costs and they are low wattage — a 135 watt red incandescent traffic light is replaced by a 10 watt LED. These advantages translate into dramatically reduced energy costs. Additionally, an incandescent red traffic light burns out at all at once which can cause serious problems, but the comparable LED consists of a hundred light emitting diodes that burn out one at a time so the red LED traffic light is still very functional until the LED is replaced.

This new technology is beginning to make headway in the marketplace. Rensselaer Polytechnic Institute's Lighting Research Center Light-Emiting Diodes website is the comprehensive website on LED traffic signals. The web site has several success stories on LED traffic signal installations as well as a report on Luminous Intensity for Traffic Signals: A Scientific Basis for Performance Specifications. The web site also includes a discussion of energy and environmental issues.

LED traffic signal
While some cities are having great success, other cities with smaller budgets are waiting for prices of LED signals to decline further. The technology used in green signals is fairly new and is more expensive than red and orange signals. Considering the labor cost of change-outs or retrofits, some city officials are delaying installation until the cost of green LEDs are lower. Lower costs will allow them to do a multiple-lamp (red and green) overhaul or a group re-lamp. Yellow signals use the less expensive technology, but are rarely used because the very short duty-cycle of yellow signals compared to red signals minimizes the effect of energy savings. Intensity requirements for yellow signals are also much higher than for red and green signals, requiring more LED components and thus more expense.

Regarding technical performance of LED traffic signals and their ability to perform safely, the Institute of Transportation Engineers has developed an Interim Purchase Specification for LED Vehicle Traffic Control Signal Modules. You can contact the Institute by phone at 202-289-0222, ext. 130. Oregon and California both have specifications regarding LED traffic signal modules. The City of Portland has published their LED Traffic Signal Success Story.

The August 4, 2004 issue of EERE Network News reports on four cities which have replaced or are in the process of replacing incandescent street lighting with LEDs.

The following press releases describe the technology, its advantages, expected annual dollar savings, and, for two of the cities, the funding mechanisms which enabled the cities to make the switch:

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