This article reports a study at the Chalmers University of Technology in Stockholm to compare the environmental impacts of light-emitting diode (LED) and incandescent-lamp traffic signals. Two sets of red, amber, and green lights were compared over a ten-year period. The older-generation LEDS tested there were built mainly from gallium arsenide (GaAs), mild steel, and epoxy resin. Contemporary LEDS use indium (In) and phosphorus (P), so that they are less dangerous and have less environmental impact than those using GaAs. Lamp housings and transparent covers are usually made of plastic materials. LEDs are made durable by mounting them on a circuit board and using copper leads for heat transfer. Although the study did not consider the environmental loads of the raw materials, it estimated the energy consumption and environmental effects of the chemicals during manufacturing. In addition, energy consumption is almost the only factor affecting the environment while the LEDs are being used. The calculation also assumes that the LEDs and circuit boards are not recycled but that the plastic front and rear are. The article tabulates summaries of the environmental impact calculations for both types of traffic signal lamp, and shows that LED lamps have about eight times less environmental impact that incandescent lamps.
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