I read that for a three light traffic signal to be converted to LED it costs about $250. Whereas, the traditional incandescents cost only $150. Your initial investment is almost double per light, and remember that most intersections have four of the three light fixtures. The article also stated that traditional bulbs cost about $73 per signal, per year. Adding up the four signals this is almost $300! Saw that you use a 20watt LED. That draws one fifth of the power, which means it should be about $60 each year. Now granted only 1/12 of the lights at the given intersection are yellow so you divide the $60 by the 12 lights you get $5 for LEDs as opposed to $25 for traditional bulbs. Finally take into consideration that the yellow light is the shortest light, which should give it the longest life span, thereby, saving you money by not replacing it as often. The difference in initial cost for the two type is about $40, for just the yellows, and at $5 per year, they should return their investment cost in just two years. Which is right about the time you would replace the traditional bulbs. After two years, let the savings begin