Future of Electric Lighting:

Light Emitting Diode (LED) technology is the future of lighting. An LED is a semiconductor
light source that does not have a fragile filament like traditional light bulbs.

LEDs are currently being used in traffic signals and street lighting, in part because they use
less energy, but the greater benefit is their longevity. It's expensive to send maintenance
people out to replace bulbs in traffic signals and LED lamps simply last much longer. 

Cities all over North America are investing LED street light to save money on electricity.
These cities also enjoy the aesthetic of a purer, whiter light than the yellowish light
produced by sodium vapor street lamps.