There are over 2300 signals on the Red, Orange, Green and Blue lines of the MBTA. Up until recently, signals used small incandescent light bulbs that lasted about six weeks; and replacing a signal bulb required two people because of safety requirements for working on a right of way. Replacing incandescent with LED technology that lasts up to 8 years is a logical step. DDP LEDS Solutions designed a direct replacement bulb at a reasonable cost. The MBTA reached their return on investment in only 4-months with a 3-year savings of over $1 million.