This study evaluated the performance of the LED modules from four manufacturers (Leotek, Gelcore, Dialight and Precision Solar) who provided the required number of LEDs for testing and evaluation at the Traffic Operations Lab. The criteria for evaluation were drivers’ perception of brightness, dottiness, and color compared to incandescent lenses. For circular red indication, brightness, dottiness, and color of Dialight LED module was similar to incandescent lens, but the other three were brighter, more dottier, and darker than incandescent lens. For circular yellow indication, brightness of Precision Solar LED was the same while the others were brighter than incandescent lens; they all were dottier and darker (orange-yellow) than incandescent lens. For circular green indication all the LED modules were brighter, dottier, darker (bluish) than incandescent lens. For yellow arrow indication, Leotek and Dialight are the same while Gelcore and Precision Solar were brighter than incandescent lens; all the LED modules were dottier and darker than incandescent lens. For green arrow indication, Leotek was the same as incandescent while Dialight, Gelcore and Precision Solar were brighter than incandescent lens; all the LED modules were dottier and darker than incandescent lens. The findings, though limited, indicated that there could be a significant difference in the perception of the LED modules by the older drivers. It is recommended to further study the effect of aging on the perception of the LED modules.The Illinois Department of Transportationpublished or submitted for publicationnot peer reviewe
