Increasing visual complexity in the roadway environment is making the task qf driving a greater challenge.for the motorist. Recent advances make it possible to produce fluorescent retroreflective materials suitable for long-term outdoor signing applications. This article presents the results of ajield study investigating the relative advantage of fluorescent colors over standard colors for detection, color recognition, and conspicuity against a complex dark background. These,fluorescent retroreflective materials are detected with higherfrequency, and recognized with greater accuracy ut jirther distunces than the corresponding standard highway colors. They also have greater uttention-getting properties (more conspicuous) during daylight than the corresponding standard highway colors. The luminance contrast ratio of'lhe sample to the camouflage background appears to correlate with the visibility/conspicuity results obtained in this study, particular1.v within a given color series.

The development of durable daylight fluorescent retroreflective sheetings has led us to investigate some of the factors that influence color measurement of these materials. the colorimetry of retroreflective materials is particularly sensitive to measurement geometry. the added aspect of fluorescence increases the spectral uncertainties, making appearance measurements even more difficult. the visual properties used to describe fluorescent retroreflective materials should include chromaticity, lightness, peak spectral radiance factor, nighttime color, and color stability on exposure. A number of test methods exist for these measurements; however, practical experience in applying these methods to fluorescent materials shows significant variation in the resulting measured values. Colorimetric measurements on commercial instruments using 45/0 (0/45) geometry, a simulated D65 illuminant, and the CIE 2° standard observer yield results that are inadequate for precise quality control of durable fluorescent retroreflective materials. the uncertainty can be reduced by the use of transfer standards, provided that the standard is similar to the sample in both hue and fluorescent emission. Ultimately, the wide availability of commercial 2‐monochromator spectrocolorimeters will be required. © 1995 John Wiley & Sons, Inc.