Welcome to brain Stuff from how Stuff works dot com where smart Happens. Hi, I'm Marshall Brain with today's question, why are they replacing all of the traffic lights with L E D s? Most cities in the United States are in the process of replacing their incandescent traffic lights with L e ED units because of three big advantages. First, L e D s are brighter. The L e ED arrays fill the entire hole and have an equal brightness
across the entire surface, making them brighter overall. Second, LED bulbs last for years, while halogen bulbs last for months. Increasing the replacement interval can save big dollars for any city. And Third, LED bulbs save a lot of energy. The energy savings can be gigantic. Assume that a traffic light uses one hundred watt bulbs today, the light is on twenty four hours a day, so it uses two and
a half kilowatt hours of electricity. It means that one traffic signal costs about twenty cents a day to operate, or about seventy three dollars a year. There are perhaps eight signals per intersections, so that's almost six hundred dollars per year. In power per intersection, and a big city has thousands of intersections, so it can cost millions of dollars just to power all the traffic lights. Led bulbs can easily save a million dollars a year or more.
These low energy bulbs also open up the possibility of using solar panels instead of running an electrical line, which saves money in remote areas. Be sure to check out our new video podcast, Stuff from the Future. Join how Stuff Work staff as we explore the most promising and perplexing possibilities of tomorrow the house Stuff Works. I Find app has arrived down at it Today on iTunes