http://www.suntimes.com/6899981-417/...hite-glow.html
City switching to street lamps that cast a white glow
BY DARRYL HOLLIDAY Staff Reporter
August 5, 2011
The yellow-orange street lamp glow Chicagoans have become accustomed to over the years is going the way of the "pretty blue lights" of Lake Shore Drive once commemorated in song.
The blue lights along Lake Shore Drive - mercury-vapor streetlamps used into the '70s - gave way to the yellow-orange lights currently used in most of the city, sodium-vapor street lamps. This week, however, the Chicago Department of Transportation announced it is installing new, energy efficient lighting on street lamps and traffic signals, which casts a white glow on city streets.
The new, metal-halide lights will use less energy than the current streetlamps. Chicago, according to CDOT officials,
is the first large U.S. city to install the relatively new technology en masse. City officials estimate an
annual $1.8 million in electrical cost savings ...