a light - emitting diode - based light source for retro - fitting into a traffic signal lamp employing an incandescent light bulb includes at least one light emitting diode , a dispersing reflector cooperating with the at least one led to adapt light produced by the at least one led for receipt by optics of the traffic signal lamp , and a screw - type electrical connector adapted to mate with a threaded socket connector of the traffic signal lamp . the screw - type electrical connector is adapted to transmit electrical power to the at least one led . a method is provided for the retro - fitting , including the step of removing the threaded light bulb from the threaded socket , and the step of connecting the threaded led light source into the threaded socket .