Color Performance of Yellow Pavement Markings at Night in the Field.

A field experiment was conducted in order to determine the perceptual color correlates of yellow pavement markings at night under tungsten-halogen and high-intensity gas discharge headlamps. Participants viewed a battery of yellow pavement markings laid out in a skipline pattern on a straight and level roadway. Four different thermoplastic pavement markings with organic yellow pigments and a waterborne latex paint type pavement marking were used. Three of the four thermoplastic pavement markings were custom tailored for the experiment, differing in their recipes of titanium-dioxide content to vary yellow saturation, while trading-off retroreflectivity. Participants were asked to identify each pavement marking color at different distances as being either yellow or white, presented in a set of six markings in a random design. No white markings were used in order to prevent relative color assessment. Spectral reflectivities and chromaticities of each pavement marking sample at each distance were measured at the National Institute for Standards and Technology. These measurements were then represented on the CIE 1931 chromaticity diagram to correlate chromaticities and perceptual color assessment for different headlamp spectra. Pavement marking type and viewing distance affected participants' responses. Headlamp type did not have a statistically significant effect. A first order interaction between pavement marking type and viewing distance was also significant, suggesting that some pavement markings preserved their yellow appearance better at far distances. A second order interaction between pavement marking type, viewing distance, and headlamp type was also statistically significant. This interaction indicates that some materials preserved their yellowness at far distances only under a specific headlamp type. Materials with less retroreflectivity appear to be less capable of rendering saturated yellow colors at long distances. The reason for this is that cones in the retina require a certain level of brightness for color perception to take place. When pavement markings drop below that level, they will generally be perceived achromatically.