Identification of pavement marking colors : executive summary.

Executive summary.PDFTech ReportST/SS/02-001SJN: 14733(0)Road markingsColorOhioWright State University. Dept. of PsychologyThomas, GinaNagy, AllenWright State University. Dept. of PsychologyOhio. Dept. of TransportationNTL-OPERATIONS AND TRAFFIC CONTROLS-Traffic Control DevicesUS Transportation CollectionThe Ohio Department of Transportation (ODOT) is charged with selecting and enforcing colorspecifications for pavement markings. In recent years, changes in materials have affected thephysical appearance of these markings. Even though, at application, the colors meet current federalspecifications, the specifications themselves are sketchy and, in some cases, given in terms of thephysical properties of the materials rather than appearance. This method is particularly troublesomesince the markings are viewed under a variety of lighting conditions and against different coloredbackgrounds (pavement types). Perhaps more of a problem is that current practice requires only asubjective evaluation of whether colors are within specification. Recently, the ODOT has also beenput under a legislative mandate to require that a certain percentage of their contracts containwarranties. This mandate makes it necessary to develop appropriate specifications for acceptablechanges in the color of pavement markings over time. Research is needed to develop thesespecifications with regard to the color appearance properties of markings. They need to be morerelevant to the needs of the driver than the current specifications, and guidelines for objectiveevaluation need to be provided. This research includes a review of current literature on color,perception, and measurement as well as a review of current practices with regard to pavementmarkings. It also includes an investigation of human perception of the color of pavement markingsunder a variety of conditions and the development of specifications, tolerances for which proceduresfor enforcement can be easily applied by the ODOT.The Commission Internationale de l\ue2\u20ac\u2122Eclairage (CIE), in 1931, developed a method for specifyingcolors. This method allows for the specification and replication of any color by associating an x andy coordinate with that color. Figure 1 shows such a diagram, which includes an artist\ue2\u20ac\u2122s rendering ofthe approximate colors in various locations. This diagram is used by both the ODOT and the FederalHighway Administration (FHWA) for specifying the color ranges of proposed pavement colorspecifications and will be used throughout this research. The current pavement marking colorspecifications are spread through a number of sources. Few of these sources provide information onsupporting research. The earliest specifications for pavement marking materials simply required thatthey be white or yellow, with yellow being reserved to mark no-passing (AASHTO [The AmericanAssociation of State Highway and Transportation Officials], 1954).Responses in the color naming experiment were similar for both daytime and nighttime viewing, forolder and younger subjects, and for a variety of pavement types. The regions in which testchromaticities met the criteria for color deficient subjects were larger for white and smaller foryellow than for normal vision subjects. These regions were, however, in much the same location.These data indicate that, using color coding, the standards that would be suggested from the colorscaling are probably the best that could be established. The only method of improvement would beredundant coding based on some dimension other than color. These results indicate that it isreasonable to establish standards and that these standards can be acceptable across a variety ofconditions and for a range of drivers.The contours that were derived from the color scaling data could reasonably be used for a newstandard. The ODOT, however, would prefer standards that allow a worker to easily and quicklydetermine if a pavement marking being measure in the field conforms. While the establishedcontours can be represented by their four corner points, a determination of whether a measurementfalls within the contour is a bit more complex. The proposed standards, on the other hand, aredefined by horizontal and vertical lines only, so that there is a range of both x and y values that acolor must fall within to meet the standard. The ODOT has indicated that they would prefer astandard of this type. In keeping with that request, boxes of this sort were established to maximizeacceptable colors and stay within the contours suggested by the color scaling data. For the whitemarkings, the range of x values is 0.33 \uc2\ub1 0.03, and the range of y values is 0.34 \uc2\ub1 0.03. For theyellow markings, the range of x values is 0.47 \uc2\ub1 0.03 and the range of y values is 0.47 \uc2\ub1 0.03