Government Technology

LEDs Save Energy, but Have Winter-Weather Drawback



December 18, 2009 By

States and cities nationwide have been retrofitting their traffic lights with light-emitting diodes (LEDs) in order to save money, add new functions to the light systems and be environmentally friendly. However, during the winter months a problem has arisen: The lights don't give off the heat that their incandescent counterparts did. Areas that experience wintry weather conditions, like Wisconsin and Minnesota, are finding that snow and ice are sometimes sticking to the lights and not melting as they had with the old bulbs.

This is causing some governments to send crews to manually remove the wintry buildup from the traffic lights so drivers can determine which color light is illuminated. This not only adds to the lights' maintenance costs, but also is dangerous for drivers. Several news outlets reported that Illinois authorities are blaming the problem on a woman's death. The woman was turning left on a green light, but a driver coming in the opposite direction didn't realize the stoplight was covered in snow and hit her vehicle, causing her death.

Although the areas that have installed LED bulbs in their traffic lights are experiencing cost savings, cities and states plagued by the winter-weather problem are looking for ways to retrofit their lights. Possible solutions include: installing weather shields, adding heat elements or coating the lights with water-repellent substances.

According to WLCO in Wisconsin, Janesville officials have received a few calls reporting that the lights were covered with snow. A police officer or Department of Public Works representative would then go to the traffic light and brush the snow off.

Earlier in the year, Government Technology covered different cities' LED installations in traffic lights.

"I think LEDs revolutionized the traffic-signal head industry," said Jim Helmer, director of San Jose, Calif's Department of Transportation, in April. "Today they burn one-tenth the energy that they did 10 years ago. So we're saving 90 percent of the power that we used to use. It is possible in streetlights to continue to reduce our power consumption and get longer lamp life, if we treat our streetlights more similar to traffic lights."

Cities also have been retrofitting their streetlights with LEDs. They can be remotely controlled from a centralized system, which allows cities to track the lights in real time and know the moment one is malfunctioning or has gone out. In August 2008, Anchorage, Alaska, purchased 4,300 LEDs for $2.2 million. Michael Barber, the city's lighting program manager, expected them to be installed by May, Government Technology reported in March. He said networking the lights is important to utilize their full capability because they are significantly more expensive -- high-pressure sodium bulbs cost about $10 each, meanwhile LEDs cost $500 to $1,000 each.

"With control systems, we can have the light tell us when there's a warranty issue or if the light goes out," Barber said. "We'll see a surge and a change in the energy consumption on that circuit."

 


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Comments

SF Hero    |    Commented December 25, 2009

Elaine - High Pressure Sodium (HPS) lamps are not used for traffic lights, incandescents are. This problem is the same as outdoor use CFL lamps, slow or no starting in cold weather AND low light output if the CFL does start. CFLs are now available that work in a wide temperature range. This is an easy problem to solve.

SF Hero    |    Commented December 25, 2009

Elaine - High Pressure Sodium (HPS) lamps are not used for traffic lights, incandescents are. This problem is the same as outdoor use CFL lamps, slow or no starting in cold weather AND low light output if the CFL does start. CFLs are now available that work in a wide temperature range. This is an easy problem to solve.

SF Hero    |    Commented December 25, 2009

Elaine - High Pressure Sodium (HPS) lamps are not used for traffic lights, incandescents are. This problem is the same as outdoor use CFL lamps, slow or no starting in cold weather AND low light output if the CFL does start. CFLs are now available that work in a wide temperature range. This is an easy problem to solve.


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