Title 23

PART 655 APPENDIX


Appendix to Subpart F of Part 655 - Alternate Method of Determining the Color of Retroreflective Sign Materials and Pavement Marking Materials

23:1.0.1.7.32.2.1.8.25 :

Appendix to Subpart F of Part 655 - Alternate Method of Determining the Color of Retroreflective Sign Materials and Pavement Marking Materials

1. Although the FHWA Color Tolerance Charts depreciate the use of spectrophotometers or accurate tristimulus colorimeters for measuring the daytime color of retroreflective materials, recent testing has determined that 0/45 or 45/0 spectroradiometers and tristimulus colorimeters have proved that the measurements can be considered reliable and may be used.

2. The daytime color of non-fluorescent retroreflective materials may be measured in accordance with ASTM Test Method E1349, “Standard Test Method for Reflectance Factor and Color by Spectrophotometry Using Bidirectional Geometry” or ASTM Test Method E 1347 (Replaces E97), “Standard Test Method for Color and Color-Difference Measurement by Tristimulus (Filter) Colorimetry.” The latter test method specified bidirectional geometry for the measurement of retroreflective materials. The geometric conditions to be used in both test methods are 0/45 or 45/0 circumferential illumination or viewing. Uniplanar geometry is not recommended for material types IV or higher (designated microprismatic). The CIE standard illuminant used in computing the colorimetric coordinates shall be D65 and the 2 Degree Standard CIE observer shall be used.

3. For fluorescent retroreflective materials ASTM E991 may be used to determine the chromaticity provided that the D65 illumination meets the requirements of E 991. This practice, however, allows only the total luminous factor to be measured. The fluorescent luminous factor must be determined using bispectral fluorescent colorimetry. Commercial instruments are available which allow such determination. Some testing laboratories are also equipped to perform these measurements.

4. For nighttime measurements CIE Standard Illuminant A shall be used in computing the colorimetric coordinates and the 2 Degree Standard CIE Observer shall be used.

5. Average performance sheeting is identified as Types I and II sheeting and high performance sheeting is identified as Type III. Super-high intensity sheeting is identified as Types V, VI, and VII in ASTM D 4956.

6. The following nine tables depict the 1931 CIE Chromaticity Diagram x and y coordinates for the corner points defining the recommended color boxes in the diagram and the daytime luminance factors for those colors. Lines drawn between these corner points specify the limits of the chromaticity allowed in the 1931 Chromaticity Diagram. Color coordinates of samples that lie within these lines are acceptable. For blue and green colors the spectrum locus is the defining limit between the corner points located on the spectrum locus:

Table 1 to Appendix to Part 655, Subpart F - Daytime Color Specification Limits for Retroreflective Material With CIE 2° Standard Observer and 45/0 (0/45) Geometry and CIE Standard Illuminant D65.

Color Chromaticity Coordinates
1 2 3 4
x y x y y x x y
White 0.303 0.300 0.368 0.366 0.340 0.393 0.274 0.329
Red 0.648 0.351 0.735 0.265 0.629 0.281 0.565 0.346
Orange 0.558 0.352 0.636 0.364 0.570 0.429 0.506 0.404
Brown 0.430 0.340 0.430 0.390 0.518 0.434 0.570 0.382
Yellow 0.498 0.412 0.557 0.442 0.479 0.520 0.438 0.472
Green 0.026 0.399 0.166 0.364 0.286 0.446 0.207 0.771
Blue 0.078 0.171 0.150 0.220 0.210 0.160 0.137 0.038
Light Blue 0.180 0.260 0.240 0.300 0.270 0.260 0.230 0.200
Purple 0.302 0.064 0.310 0.210 0.380 0.255 0.468 0.140