The lifespan of an LED street light is determined by its light output compared to its original design specification. Once its brightness decreases by 30 percent, an LED street light is considered to be at the end of its life. Most LED street lights have a lens on the LED panel, which is designed to cast its light in a rectangular pattern, an advantage compared to traditional street lights, which typically have a reflector on the back side of a high-pressure sodium lamp. In this case, much of the luminance of the light is lost and produces light pollution in the air and surrounding environment.
