Effects of Sweeping, Color and Luminance Distribution on Response to Automotive Stop Lamps

Immediate response to stop lamps when driving is crucial to roadway safety. Previous research has demonstrated that neon and light emitting diode (LED) stop lamps that have a dynamic sweeping luminance distribution can be just as or more effective than standard stop lamps. Sweeping neon and LED lamps with sweep-up times equal to or less than 100 ms resulted in reaction times equal to or shorter than those obtained with a conventional, non-sweeping incandescent stop lamp. At the same time, an LED stop lamp having the same far-field luminous intensity characteristics as the neon lamp, resulted in shorter reaction times than the neon lamp. The LED stop lamp differed from the neon lamp in two important ways. First, its color was different; the LED lamp had a dominant wavelength of about 630 nm, in comparison to the neon lamp with a dominant wavelength of about 615 nm. Second, the luminance distribution of the LED lamp consisted of a series of high-luminance point sources, compared with the neon lamp, which was a diffuse luminous tube having a lower overall luminance. A series of experimental investigations is described with the objective of quantifying the relative impact of color and luminance distribution on vi sual response of stop lamps. The implications of the color and luminance distribution results of this study will be discussed with respect to stop lamp design and regulations.