The colorimetric properties of seventy-four samples of retroreflective highway sign materials were obtained at NBS by visual measurements outdoors using five observers having normal color vision, and by three photoelectric tristimulus colorimeters and a recording spectrophotometer. Cooperative measurements by two industrial color laboratories are also reported.

Verhead Guide Signs can be illuminated to sufficient target value and uniformity with certain 100 watt mercury vapor lighting units. Coating materials based on thermal setting polyester, and thermal setting polyvinylidene fluoride have been found to be satisfactory coating materials for Overhead Guide Signs. Preliminary field evaluations and legibility studies indicate that approximately 40% of the Overhead Guide Signs in the State would not require illumination if the legend is reflective.