Colors of retroreflective traffic sign materials when illuminated by high-intensity-discharge headlights.

This analytical study evaluated the colorimetric properties of retroreflective traffic signs when illuminated by high- intensity- discharge (HID) headlamps. Two aspects were investigated; (1) colorimetric shifts of individual sign materials when illuminated by HID light sources as opposed to halogen, and (2) colorimetric separations of the red sign material from the yellow, orange, and brown sign materials when illuminated by HID light sources.