ASTM D4061-13(2018)
(Test Method)Standard Test Method for Retroreflectance of Horizontal Coatings
Standard Test Method for Retroreflectance of Horizontal Coatings
SIGNIFICANCE AND USE
5.1 The quantity coefficient of retroreflected luminance is a measure of the reflected luminance in the direction of the observer. This is the light returned by the retroreflective surface to the observer from the source, which in practice is the vehicle headlamp.
5.2 This test method may be used as a measure of the nighttime performance of horizontally applied surfacing materials used on highway surfaces for lane markings and other traffic control purposes.
5.3 Since this test method is a laboratory procedure, test specimens must be prepared so that they can be mounted on the specimen holder. Specimens measured by this laboratory method may be 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.
SCOPE
1.1 This test method describes the instrumental measurement of the retroreflective 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 test method. Likewise, the user must specify the observation and entrance angles to be used (see Fig. 1).
FIG. 1 Diagram Illustrating Geometry for Measurement of Horizontal Coatings Specimens
Note 1: Includes observation angle α, entrance angle β, viewing angle νa, co-viewing angle νc, and co-entrance angle βc. The retroreflector axis, illumination axis, and observation axis all lie in the same plane.
1.3 The geometric requirements of this test 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.
FIG. 2 Illustration of Typical Rate of Change of Retroreflectance Versus Observation Angle for Horizontal Retroreflective Material Measured at 86° Entrance Angle
1.4 This test method is a laboratory test and requires a facility that can be darkened sufficiently so that stray light does not affect the test results. This facility must be capable of housing the required 15-m test distance.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
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Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation:D4061 −13 (Reapproved 2018)
Standard Test Method for
Retroreflectance of Horizontal Coatings
This standard is issued under the fixed designation D4061; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
2.1 ASTM Standards:
1.1 This test method describes the instrumental measure-
E284Terminology of Appearance
ment of the retroreflective properties of horizontal surfacing
E308PracticeforComputingtheColorsofObjectsbyUsing
materials, such as traffic stripe paint systems, traffic tapes, and
the CIE System
traffic surface symbols.
E691Practice for Conducting an Interlaboratory Study to
1.2 Specimen preparation, size, and shape must be deter-
Determine the Precision of a Test Method
mined and specified by the user of this test method. Likewise,
E808Practice for Describing Retroreflection
theusermustspecifytheobservationandentranceanglestobe
E809Practice for Measuring Photometric Characteristics of
used (see Fig. 1).
Retroreflectors
2.2 CIE Publication:
1.3 The geometric requirements of this test method are
No. 54Retroreflection Definition and Measurement
based on materials for which the relative retroreflectance
changes less than approximately 50% over the observation
3. Terminology
angle range from 0.2 to 0.5°. This is illustrated in Fig. 2.
3.1 The terms and definitions inTerminology E284 apply to
1.4 This test method is a laboratory test and requires a
this test method.
facilitythatcanbedarkenedsufficientlysothatstraylightdoes
3.2 Definitions:
not affect the test results. This facility must be capable of
3.2.1 coeffıcient of retroreflected luminance, R ,n—ratio of
L
housing the required 15-m test distance.
the luminance, L, of a projected surface to the normal
1.5 The values stated in SI units are to be regarded as
illuminance, E , at the surface on a plane normal to the
'
standard. No other units of measurement are included in this
incident light, expressed in candelas per square metre per lux
−2 −1
standard.
(cd·m ·lx ).
1.6 This standard does not purport to address all of the R 5 ~L/E ! (1)
L '
safety concerns, if any, associated with its use. It is the
3.2.2 datum mark, n—in retroreflection,anindicationonthe
responsibility of the user of this standard to establish appro-
retroreflector that is used to define the orientation of the
priate safety, health, and environmental practices and deter-
retroreflector with respect to rotation about the retroreflector
mine the applicability of regulatory limitations prior to use.
axis.
1.7 This international standard was developed in accor-
3.2.2.1 Discussion—The datum mark must not lie on the
dance with internationally recognized principles on standard-
retroreflector axis.
ization established in the Decision on Principles for the
3.2.3 entrance angle, β, n—in retroreflection,anglebetween
Development of International Standards, Guides and Recom-
the illumination axis and the retroreflector axis.
mendations issued by the World Trade Organization Technical
3.2.3.1 Discussion—For plane retroreflective surfaces, the
Barriers to Trade (TBT) Committee.
entrance angle is no larger than 90°.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
This test method is under the jurisdiction of ASTM Committee E12 on Color contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
and Appearance and is the direct responsibility of Subcommittee E12.10 on
Standards volume information, refer to the standard’s Document Summary page on
Retroreflection.
the ASTM website.
Current edition approved Oct. 1, 2018. Published October 2018. Originally AvailablefromU.S.NationalCommitteeoftheCIE(InternationalCommission
approved in 1989. Last previous edition approved in 2013 as D4061–13. DOI: on Illumination), C/o Thomas M. Lemons, TLA-Lighting Consultants, Inc., 7 Pond
10.1520/D4061-13R18. St., Salem, MA 01970, http://www.cie-usnc.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4061−13 (2018)
collector such as an integrating sphere, if used, often the
monochromator or spectral filters, the detector, and associated
optics and electronics.
3.2.9 retroreflection, n—reflection in which the reflected
rays are preferentially returned in directions close to the
opposite of the direction of the incident rays, this property
being maintained over wide variations of the direction of the
B
incident rays. [CIE]
3.2.10 retroreflector axis, n—a designated line segment
from the retroreflector center that is used to describe the
angular position of the retroreflector.
NOTE 1—Includes observation angle α, entrance angle β, viewing angle
3.2.10.1 Discussion—Thedirectionoftheretroreflectoraxis
ν , co-viewing angle ν , and co-entrance angle β . The retroreflector axis,
a c c
is usually chosen centrally among the intended directions of
illumination axis, and observation axis all lie in the same plane.
illumination;forexample,thedirectionoftheroadonwhichor
FIG. 1Diagram Illustrating Geometry for Measurement of
with respect to which the retroreflector is intended to be
Horizontal Coatings Specimens
positioned. In testing horizontal road markings the retroreflec-
tor axis is usually the normal to the test surface.
3.2.11 rotation angle, ε,n—angle indicating the orientation
ofthespecimenwhenitisrotatedaboutaselectedaxisfixedin
it (for plane specimens, usually the specimen normal); in
retroreflection, the dihedral angle from the half-plane originat-
ingontheretroreflectoraxisandcontainingthepositivepartof
the second axis to the half-plane originating on the retroreflec-
tor axis and containing the datum mark.
3.2.11.1 Discussion—The rotation angle shown in Fig. 3,
with the datum mark oriented away from the source, is 0°.
3.2.12 source, n—an object that produces light or other
radiant flux.
FIG. 2Illustration of Typical Rate of Change of Retroreflectance 3.2.13 specific luminance—see coefficient of retroreflected
Versus Observation Angle for Horizontal Retroreflective Material
luminance.
Measured at 86° Entrance Angle
3.2.14 viewing angle, ν—the angle between the observation
axis and the retroreflector axis.
3.2.3.2 Discussion—Theentranceanglemaybedividedinto 3.2.14.1 Discussion—In testing road markings specimens,
components β and β . This is described in Practice E808.In the retroreflector axis is usually the normal to the test surface
1 2
this test method only the component β is used. Therefore, (see definition of retroreflector axis).
where only the entrance angle β is specified the convention
3.3 Definitions of Terms Specific to This Standard:
used is β =0 and β =β.
2 1
3.3.1 co-entrance angle, β,n—the complement of the
c
3.2.4 illumination axis, n—in retroreflection, a line from the
entrance angle (90°−β).
effective center of the source aperture to the retroreflector
3.3.1.1 Discussion—On a typical test specimen, this is the
center.
angle from the plane surface of the material to the observation
axis.
3.2.5 normal illuminance, E —theilluminanceonaretrore-
'
flective surface measured in the plane that passes through the
3.3.2 co-viewing angle, ν,n—the complement of the view-
c
retroreflector center and is perpendicular to the illumination
ing angle (90°−η).
−2
axis; measured in lux (lumens·m ).
4. Summary of Test Method
3.2.6 observation angle, n—angle between the axes of the
incident beam and the observed (reflected) beam, (in
4.1 This test method involves the use of a light-projector
retroreflection, α, between the illumination axis and the obser-
source, a photoreceptor, a specimen holder, and a receptor-
vation axis).
source support, all arranged with approximately 15-m separa-
3.2.6.1 Discussion—The observation angle is always posi-
tion between the specimen holder and receptor-source support
tive and in the context of retroreflection is restricted to small
in a suitable darkened area. The observation angle is generally
acute angles.
small (0.2 to 2.0°) and the entrance angle approaches 90° (the
light is near the grazing angle).
3.2.7 observation axis, n—in retroreflection, a line from the
effective center of the receiver aperture to the retroreflector
4.2 The general procedure is to determine the ratio of the
center.
retroreflected light from the test surface to the incident light on
3.2.8 receiver, n—the portion of a photometric instrument the test surface. From these measurements, the photometric
that receives the viewing beam from the specimen, including a quantity, specific luminance is calculated.
D4061−13 (2018)
FIG. 3Arrangement of Test Apparatus
5. Significance and Use tion of the 1931 CIE Standard Source A (a correlated color
temperature of 2856 K). A method for determining correlated
5.1 The quantity coefficient of retroreflected luminance is a
color temperature is contained in Annex A3 of Practice E809.
measure of the reflected luminance in the direction of the
6.1.2 Exit Aperture—The source exit aperture shall be 43
observer.Thisisthelightreturnedbytheretroreflectivesurface
mm maximum diameter. This corresponds to 10 min of arc
totheobserverfromthesource,whichinpracticeisthevehicle
angular aperture at 15 m test distance. In practice, it is
headlamp.
convenient to provide the projection with a non-silvered right
5.2 This test method may be used as a measure of the
angle prism so that the external physical size of the exit
nighttime performance of horizontally applied surfacing mate-
aperture is small, allowing its close proximity to the entrance
rials used on highway surfaces for lane markings and other
aperture of the photoreceptor.
traffic control purposes.
6.1.3 Illuminated Area—The illumination at the specimen
produced by the projector shall be such that only the test
5.3 Since this test method is a laboratory procedure, test
specimensmustbepreparedsothattheycanbemountedonthe surface and a minimum of the background is illuminated. This
is commonly accomplished by placing a restrictive aperture in
specimen holder. Specimens measured by this laboratory
method may be used as transfer standards for the calibration of the projector slide port.
6.1.4 Source Stability—The source shall be regulated such
portable instrumentation.
that the illumination at the test surface does not change by
5.4 Specimen selection and preparation may significantly
more than 61% for the duration of the test.
influence the results of this test method.
6.1.5 Illumination Uniformity—The illumination produced
on the specimen surface shall be uniform within 65% of the
6. Apparatus
average illuminance normal to the source at the test distance.
6.1 Light Source, projector type, meeting the following
6.2 Photoreceptor, meeting the following requirements:
requirements:
6.2.1 Sensitivity—The photoreceptor shall have sufficient
6.1.1 Color Temperature—The projection lamp together
sensitivity and range so that readings of both the incident
with the projection optics shall be operated so that they
illuminance and the retroreflected light at the observation
illuminate the test specimen with the spectral energy distribu-
4 5
Acommercial slide projector with 7-in. F-3.5 lens and with the heat absorbing See Practice E308, Table3.
filter removed has been found satisfactory as a light source. Such a projector must A slide with a 3- by 15-mm opening has been found satisfactory.
be run at reduced voltage to achieve the required color temperature and to provide Commercially available instruments commonly referred to as telephotometers
adequate lamp stability. have been found satisfactory for this purpose.
D4061−13 (2018)
6.3.1 Angular Accuracy—The test surface must be position-
ablesothattheentranceangleisaccuratetowithin0.5%ofits
complement (that is, for 86° entrance angle, the angle must be
accurateto0.005×4°=0.02°).Thisaccuracymaybeobtained
by providing an optical means to align the test surface to 90°
entranceangleandthenadjustingtothedesiredentranceangle.
(See Figs. 6-9 for examples of angular setting devices.)
6.3.2 Entrance Angle Axis—A means must be provided to
change the entrance angle such that the axis of rotation is
contained in the plane of the test surface if several entrance
angles are to be used.
6.3.3 Leading Edge Reflections—The specimen holder must
be provided with a means of eliminating reflections from the
leading edge of the specimen, and the holder itself must be
non-reflective.
6.3.4 Incident Light Measurement Provision—It is desirable
that the specimen holder be such that the photoreceptor can
easily be substituted for the specimen, which is required when
incident light measurements are taken.
6.4 Receptor-Source Support—A device that adequately
supportsandseparatesthephotoreceptorfromthesourceatthe
FIG. 4Example of Specimen Holder Using Machinist’s Rotary
observation position. The required accuracy of separation of
Table
the source exit aperture from the photoreceptor entrance
aperture is dependent on the properties of the test specimen.
position can be measured with a resolution of at least 1 part in
For most horizontal surfacing materials, the divergence pat-
50 on the readout scale.
terns are gradual and a positioning accuracy of 61mm(or
6.2.2 Spectral Response—The spectral response of the pho-
60.5% of the resolution) at 15 m test distance is adequate.A
toreceptor shall match that of the 1931 CIE Standard Photopic
common method of fixing this distance is to provide a bar with
Observer. See Annex A1 of Practice E809.
holesmachinedinitatseparationscorrespondingtothedesired
6.2.3 Stability—The receptor response shall not vary more
observation angles. In this method, the minimum practical
than 61% for the duration of the test.
observation angle is about 0.2°.
6.2.4 Linearity—The linearity of the photometric scale over
6.5 Photometric Site—Sufficient space is required so that
the range of readings to be taken shall be within 61%.
the projector source and test surface can be separated by about
Correction factors may be used to ensure linear response. A
15 m. This facility must be such that stray light does not
methodfordetermininglinearityiscontainedinPracticeE809,
appreciably affect the test results. Flat black paint, black
Annex A2.
curtains,blacktape,andothermeansshallbeusedtoeliminate
6.2.5 Field of View—The field of view shall be limited by
unwanted light and stray reflections.
use of l
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