You have probably seen more and more traffic signals being converted from conventional incandescent light bulbs to LED's. You may also realize that the main benefit is the cost savings from not needing crews to replace the burned out bulbs on a yearly basis. An LED signal will last seven years or more.

You may not have realized several other really neat benefits.

I think the coolest one is this: Obviously the signals use much less power than the traditional ones. I think it is something like only 10% of a traditional signal. Because of this it becomes feasible during black outs to run an entire intersection's signals on a few deep cycle marine batteries for a few hours! So not only does converting an intersection to LED save a city ton of money each year in electricity, it increases safety.