However, the relatively small lumen package that is produced by a single LED still means that dozens, if not hundreds, of LEDs must be used together to produce even a modest amount of light. The spectral power distribution of an LED is fairly narrow, with half-bandwidths of around 20 to 50 nm, depending upon the substrate material. This means that LEDs produce highly saturated, nearly monochromatic light. White light can also be generated by mixing the light generated by blue, green and red LEDs. LED traffic signals.
Several companies manufacture traffic signals using LEDs.
Of course, signals such as directional arrows require fewer LEDs, in contrast to a stencil that is typically used with incandescent traffic signal arrow heads. Lighting Research Center , Rensselaer Polytechnic Institute , and Pacific Gas and Electric Company . All rights reserved.