ASTM D4061-13 (R2018) pdf free download.Standard Test Method for Retroreflectance of Horizontal Coatings.
1. 1 This test method describes the instrumental measurement of the retrorellective properties of horizontal surfacing materials, such as traffic stripe paint systems. traffic tapes, and traffic surface symbols.
1.2 Specimen preparation, size, and shape must be determined and specified by the user of this lest method. Likewise, the user must specify the observation and entrance angles to be used (see Fig. I).
1.3 The geometnc requirements of this lest method are based on materials for which the relative retroreflectance changes less than approximately 50 % over the observation angle range from 0.2 to 0.5°. This is illustrated in Fig. 2.
1 .4 This lest method is a laNwalory test and requires a facility that can be darkened sufficiently so that stray light does not atkct the test results. This facility must be capable of housing the required 15-rn Lest distance.
1.5 The values stated in SI units are to he regarded as standard. No other units of measurement arc included in this standard.
5. Significance and Use
5.1 The quantity coefficient of retroreflected luminance is a measure of (he reflected luminance in the direction ot’ the observer. This is the light returned by the retroretlective surface to the observer from the source, which in practice is the vehicle head lamp.
5.2 This test method may be used as a measure of the nightti nie performance of horitontally applied surfacing materials used on highway surfaces for lane markings and other traffic control purposes.
5.3 Since this test method is a laboratory proeedure. test specimens must be prepared so that they can be mounted on the specimen holder. Specimens measured by this laboratory method may he used as transfer standards for the calibration of portable instrumentation.
5.4 Specimen selection and preparation may significantly influence the results of this test method.
6. Apparatus
6.1 Light Source, projector type, meeting the following requirements:
6.1.2 Exit Aperture—The source exit aperture shall be 43 mm maximum diameter. This corresponds to 10 mm of arc angular aperture at 15 111 test distance. In practice, it is convenient to provide the projection with a non-silvered right angle prism so that the external physical size of the exit aperture is small. allowing its close proximity to the entrance aperture of the phowreceptor.ASTM D4061 pdf download.