1. LawStack
  2. Title 23 - Highways
  3. Chapter I - FEDERAL HIGHWAY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION
  4. Subchapter G - ENGINEERING AND TRAFFIC OPERATIONS
  5. Part 655 - TRAFFIC OPERATIONS
  6. Subpart F - Traffic Control Devices on Federal-Aid and Other Streets and Highways
  7. 23 CFR Appendix to Subpart F of Part 655
23 CFR Appendix to Subpart F of Part 655
Alternate Method of Determining the Color of Retroreflective Sign Materials and Pavement Marking Materials
May 21, 2020
CFR

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.

Open Table
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

Table 1a to Appendix to Part 655, Subpart F—Daytime Luminance Factors (%) for Retroreflective Material With CIE 2° Standard Observer and 45/0 (0/45) Geometry and CIE Standard Illuminant D65.

Open Table
Color Daytime Luminance Factor (Y %) by ASTM Type
Types I, II, III and VI Types IV, VII, and VIII Type V
Minimum Maximum Minimum Maximum Minimum Maximum
White 27 40 15
Red 2.5 12 3.0 15 2.5 11
Orange 14 30 12 30 7.0 25
Brown 4.0 9.0 1.0 6.0 1.0 9.0
Yellow 15 45 24 45 12 30
Green 3.0 9.0 3.0 12 2.5 11
Blue 1.0 10 1.0 10 1.0 10
Light Blue 12 40 18 40 8.0 25
Purple 2.0 10 2.0 10 2.0 10

Table 2 to Appendix to Part 655, Subpart F—Nighttime Color Specification Limits for Retroreflective Material With CIE 2° Standard Observer and Observation Angle of 0.33°, Entrance Angle of + 5° and CIE Standard Illuminant A.

Open Table
Color Chromaticity Coordinates
1 2 3 4
x y x y x y x y
White 0.475 0.452 0.360 0.415 0.392 0.370 0.515 0.409
Red 0.650 0.348 0.620 0.348 0.712 0.2550 0.735 0.265
Orange 0.595 0.405 0.565 0.405 0.613 0.355 0.643 0.355
Brown 0.595 0.405 0.540 0.405 0.570 0.365 0.643 0.355
Yellow 0.513 0.487 0.500 0.4700 0.545 0.425 0.572 0.425
Green 0.007 0.570 0.200 0.500 0.322 0.590 0.193 0.782
Blue 0.033 0.370 0.180 0.370 0.230 0.240 0.091 0.133
Purple 0.355 0.088 0.385 0.288 0.500 0.350 0.635 0.221
Light Blue Chromaticity coordinates are yet to be determined.

Note: Materials used as High-Conspicuity, Retroreflective Traffic Signage Materials shall meet the requirements for Daytime Color Specification Limits, Daytime Luminance Factors and Nighttime Color Specification Limits for Fluorescent Retroreflective Material, as described in Tables 3, 3a, and 4, throughout the service life of the sign.

Table 3 to Appendix to Part 655, Subpart F—Daytime Color Specification Limits for Fluorescent Retroreflective Material with CIE 2° Standard Observer and 45/0 (0/45) Geometry and CIE Standard Illuminant D65.

Open Table
Color Chromaticity Coordinates
1 2 3 4
x y x y x y x y
Fluorescent Orange 0.583 0.416 0.535 0.400 0.595 0.351 0.645 0.355
Fluorescent Yellow 0.479 0.520 0.446 0.483 0.512 0.421 0.557 0.442
Fluorescent Yellow-Green 0.387 0.610 0.369 .546 .428 .496 0.460 0.540
Fluorescent Green 0.210 0.770 0.232 0.656 0.320 0.590 0.320 0.675
Fluorescent Pink 0.450 0.270 0.590 0.350 0.644 0.290 0.536 0.230
Fluorescent Red 0.666 0.334 0.613 0.333 0.671 0.275 9.735 0.265

Table 3a to Appendix to Part 655, Subpart F—Daytime Luminance Factors (%) for Fluorescent Retroreflective Material With CIE 2° Standard Observer and 45/0 (0/45) Geometry and CIE Standard Illuminant D65.

Open Table
Color Luminance Factor Limits (Y)
Min Max YF*
Fluorescent Orange 25 None 15
Fluorescent Yellow 45 None 20
Fluorescent Yellow-Green 60 None 20
Fluorescent Green 20 30 12
Fluorescent Pink 25 None 15
Fluorescent Red 20 30 15

*Fluorescence luminance factors (YF) are typical values, and are provided for quality assurance purposes only. YF shall not be used as a measure of performance during service.

Table 4 to Appendix to Part 655, Subpart F—Nighttime Color Specification Limits for Fluorescent Retroreflective Material With CIE 2° Standard Observer and Observation Angle of 0.33°, Entrance Angle of + 5° and CIE Standard Illuminant A.

Open Table
Color Chromaticity Coordinates
1 2 3 4
x y x y x y x y
Fluorescent Orange 0.625 0.375 0.589 0.376 0.636 0.330 0.669 0.331
Fluorescent Yellow 0.554 0.445 0.526 0.437 0.569 0.394 0.610 0.390
Fluorescent Yellow-Green 0.480 0.520 0.473 0.490 0.523 0.440 0.550 0.449
Fluorescent Green 0.007 0.570 0.200 0.500 0.322 0.590 0.193 0.782
Fluorescent Red 0.680 0.320 0.645 0.320 0.712 0.253 0.735 0.265

Table 5 to Appendix to Part 655, Subpart F—Daytime Color Specification Limits for Retroreflective Pavement Marking Material With CIE 2° Standard Observer and 45/0 (0/45) Geometry and CIE Standard Illuminant D65.

Open Table
Color Chromaticity Coordinates
1 2 3 4
x y x y x y x y
White 0.355 0.355 0.305 0.305 0.285 0.325 0.335 0.375
Yellow 0.560 0.440 0.490 0.510 0.420 0.440 0.460 0.400
Red 0.480 0.300 0.690 0.315 0.620 0.380 0.480 0.360
Blue 0.105 0.100 0.220 0.180 0.200 0.260 0.060 0.220
Purple 0.300 0.064 0.309 0.260 0.362 0.295 0.475 0.144

Table 5a to Appendix to Part 655, Subpart F—Daytime Luminance Factors (%) for Retroreflective Pavement Marking Material With CIE 2° Standard Observer and 45/0 (0/45) Geometry and CIE Standard Illuminant D65.

Open Table
Color Luminance Factor (Y%)
Minimum Maximum
White 35
Yellow 25
Red 6 15
Blue 5 14
Purple 5 15

Table 6 to Appendix to Part 655, Subpart F—Nightime Color Specification Limits for Retroreflective Pavement Marking Material With CIE 2° Standard Observer, Observation Angle of 1.05°, Entrance Angle of + 88.76° and CIE Standard Illuminant A.

Open Table
Color Chromaticity Coordinates
1 2 3 4
x y x y x y x y
White 0.480 0.410 0.430 0.380 0.405 0.405 0.455 0.435
Yellow 0.575 0.425 0.508 0.415 0.473 0.453 0.510 0.490
Purple 0.338 0.080 0.425 0.365 0.470 0.385 0.635 0.221

Note: Luminance factors for retroreflective pavement marking materials are for materials as they are intended to be used. For paint products, that means inclusion of glass beads and/or other retroreflective components.

[67 FR 49572, July 31, 2002, as amended at 67 FR 70163, Nov. 21, 2002; 68 FR 65582, 65583, Nov. 20, 2003; 74 FR 66862, 66863, Dec. 16, 2009]

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