Ranges of Stop Sign Chromaticity under Tungsten-Halogen and High-IntensityDischarge Illumination

摘要

The development of high-intensity discharge (HID) sources for automotiveheadlighting has raised questions about the rendering of colors by those sources, relative to the rendering of colors by tungsten-halogen sources. The rendering of sign colors has been of concern because color is used as an indicator of sign functions. The rendering of the red of stop signs has been particularly of concern because consistent recognition of stop signs is critical for safety. The study was designed to compare the magnitudes of the shifts in chromaticity of stop signs illuminated by HID and tungsten-halogen headlamps to the range of chromaticities of stop signs under tungsten-halogen. A stratified sample of 25 stop signs was selected in Ann Arbor, Michigan. Stratification wasby material (enclosed, encapsulated, microprism), age (more than five years in service, less than one year in service), and compass direction faced by the legend side of the sign (north, south). The chromaticities of these signs were measured in the field under both tungsten-halogen and HID (D1) illumination. The shifts between the chromaticities of the signs when they were illuminated with the tungsten-halogen source and when they were illuniated with the HID light source were moderate relative to the range of chromaticities under tungsten-halogen.