Currently, incandescent lamps are the predominant source for traffic signal lighting. Yet, incandescent lamps are inherently inefficient in converting electrical energy into light when compared to other light sources. The useful life of an incandescent lamp is also much shorter than other sources. As a result, maintenance costs are high, and the lamps must be changed many times during the life of the signal head. Furthermore, the effective light output of an incandescent lamp decreases over its life.

All of these disadvantages of the incandescent lamp, when coupled with the increasing cost of electrical energy, make it important and timely to consider a more economical light source such as light emitting diodes (LEDs). Although there are other light source technologies that could replace incandescent lamps, this project is limited to applications of LEDs to all types of traffic control signal indications.

The objectives of the project were: (1) to determine the feasibility and implementation potential of LEDs for traffic control signal indications, i.e., vehicle, pedestrian, and lane-use; (2) to demonstrate and evaluate the technology in both laboratory and field applications; and (3) to provide recommendations for needed changes to current traffic control signal standards.

All research is complete. The conclusions and recommendations have been published in Research Results Digest 205, "Requirements for Application of Light Emitting Diodes (LEDs) to Traffic Control Signals."