1、Designation: E 2302 03a (Reapproved 2009)Standard Test Method forMeasurement of the Luminance Coefficient Under DiffuseIllumination of Pavement Marking Materials Using a PortableReflectometer1This standard is issued under the fixed designation E 2302; the number immediately following the designation
2、 indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers measurement o
3、f the luminancecoefficient under diffuse illumination of horizontal pavementmarkings, such as traffic stripes and surface symbols, andpavement surfaces, in a particular viewing direction using aportable reflectometer.NOTE 1The luminance coefficient under diffuse illumination is ameasure of the refle
4、ction of horizontal pavement markings and pavementsurfaces in a particular viewing direction in daylight or under roadlighting. Diffuse illumination approximates daylight illumination from theovercast sky, and road lighting as an average of locations on the pavementsurface.1.2 The co-viewing angle o
5、f the reflectometer affects thereadings. As specified by the European Committee for Stan-dardization (CEN), the co-viewing angle shall be 2.29.1.3 This test method is intended to be used for fieldmeasurement of pavement markings and pavement surfaces butmay be used to measure the performance of mate
6、rials onsample panels before placing the marking material in the field.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine th
7、e applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E 284 Terminology of AppearanceE 809 Practice for Measuring Photometric Characteristicsof Retroreflectors2.2 Other Standard:CEN EN 1436 Road Marking MaterialsRoad MarkingPerformance for Road Users33. T
8、erminology3.1 The terminology used in this test method generallyagrees with that used in Terminology E 284.3.2 Definitions:3.2.1 luminance coeffcient under diffuse illumination; Qd,nthe ratio of luminance, L, in a particular viewing direction,of a projected surface to the illuminance of diffuse illu
9、mina-tion, E, at the surface on the plane of the surface, expressed incandelas per square metre per lux (cdm-2lx-1).3.2.1.1 DiscussionQd has a range from zero up to amaximum of 1/p = approximately 0.318 cdm-2lx-1. Forconvenience, the units used commonly are millicandelas persquare metre per lux (mcd
10、m-2lx-1) providing a range fromzero up to 1000/p = approximately 318 mcdm-2lx-1.3.2.2 co-viewing angle, a, nthe angle between the planeof the pavement marking surface and the observation axis.3.2.3 portable reflectometer, na hand-held instrument thatcan be used in the field or laboratory for measure
11、ment ofluminance coefficient under diffuse illumination.3.2.4 instrument standard, nworking standard used tostandardize the portable reflectometer.4. Summary of Test Method4.1 This test method involves the use of commercial por-table reflectometers for determining the luminance coefficientunder diff
12、use illumination in a particular viewing direction ofhorizontal coatings materials used in pavement markings.4.2 The co-viewing angle is fixed at 2.29.4.3 The reflectometers use an external panel or other instru-ment standard of known luminance coefficient under diffuseillumination, Qd.4.4 The porta
13、ble reflectometer is placed directly over thepavement marking to be measured, ensuring that the measure-ment area of the reflectometer fits within the width of thestripe, and the reading displayed by the reflectometer isrecorded.1This test method is under the jurisdiction of ASTM Committee E12 on Co
14、lorand Appearance and is the direct responsibility of Subcommittee E12.10 onRetroreflection.Current edition approved Aug. 1, 2009. Published September 2009. Originallyapproved in 2003. Last previous edition approved in 2003 as E 2302 03a.2For referenced ASTM standards, visit the ASTM website, www.as
15、tm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from European Committee for Standardization (CEN), 36 rue deStassart, B-1050, Brussels, Belgium, http:/www.cenor
16、m.be.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.5 Readings shall be taken for the direction of traffic.Readings shall be taken for each direction of traffic separatelyfor centerlines.5. Significance and Use5.1 The quality of t
17、he stripe for visibility in daylight orunder road lighting is determined by the luminance coefficientunder diffuse illumination, Qd, and depends on the materialsused, age, and wear pattern. These conditions shall be observedand noted by the user.5.2 Under the same conditions of illumination and view
18、ing,higher levels of Qd correspond to higher levels of lightness.5.3 Reflectivity of pavement (road) markings degrade withtraffic wear and require periodic measurement to ensure thatsufficient line visibility is provided to drivers.5.4 For a given viewing distance, measurements of Qd madewith a refl
19、ectometer having a geometry corresponding to thatdistance are a good indicator of the visual ranking of materialmeasured.5.5 specified by CEN, the measurement geometry of theinstrument is based on a viewing distance of 30 m and an eyeheight of 1.2 m.5.6 It shall be the responsibility of the user to
20、employ aninstrument having the specified co-viewing angle.6. Apparatus6.1 Portable Reflectometer:6.1.1 The reflectometer shall be portable, with the capabilityto be placed on various horizontal pavement markings indifferent locations.6.1.2 The reflectometer shall be constructed so that place-ment on
21、 the highway pavement markings will preclude anystray light entering the measurement area of the instrument andaffecting the reading. This may be done by shielding againststray light, or by subtraction of the stray light reading, or both.Alternatively, the reflectometer shall produce a warning signa
22、lwhen stray light could affect the reading.6.1.3 For the convenience of the user, a marking shall beplaced on the instrument to permit it to be aligned with thedirection of traffic, or the instrument design shall itself indicatethe measuring direction in an obvious manner.6.2 Illumination System Req
23、uirements:6.2.1 The illumination system shall provide diffuse illumi-nation, which can be obtained by indirect illumination througha sample gate from a photometric sphere of interior white, mattfinish.6.2.2 The illumination system shall have compensation forthe increase of illumination caused by int
24、erreflection betweena sample surface and the interior surfaces of the illuminationsystem, for instance by means of a reading of the illuminanceat a location close to the sample gate.6.2.3 The diffuse illumination may be approximated byreflection from the interior surface of sphere or other shape orb
25、y other means. Enough testing shall be carried out to verifythat flux received on the sample is approximately homoge-neous. For measurements from all positions in the sample gateand in all directions, using a collection cone of an includedangle of 8 degrees the ratio of the smallest to the largestme
26、asurement shall be minimum 0.8. The test shall be carriedout with the sample gate open, and shall be repeated with thesample gate closed by a reflecting surface of white, matt finishwith suitable openings to allow for the measurements.6.2.3.1 The case of illumination by a sphere with a bottomapertur
27、e is shown in Fig. 1. For this arrangement sample gateshould not be larger than necessary in view of the illuminatedarea needed in accordance with 6.4 and should stop at adistance before the sphere surface opposing the observationdirection. In order that reflection in the sample surface shall notdis
28、tort the uniformity of luminance of the interior spheresurface, the remaining part of the sphere, after introducing thebottom aperture, shall be minimum 0.83D, where D is thediameter of the sphere. In this case, the test of 6.2.3 needs onlyto be applied with the sample gate open.6.2.4 The sphere may
29、 be approximated by other shapes, butenough testing shall be carried out to verify that interiorsurfaces have approximately constant luminance. The ratio ofthe smallest to the largest luminance of interior surfaces shallbe minimum 0.8, when measured in different directionsthrough different locations
30、 at the sample gate. The test shall becarried out with the sample gate open, and shall be repeatedwith the sample gate closed by a reflecting surface of white,matt finish with suitable openings to allow for the measure-ments.6.3 Receiver Requirements:6.3.1 The receiver shall have sufficient sensitiv
31、ity and rangeto accommodate luminance coefficient in diffuse illuminationexpected in use, typically from 1 to close to the maximum ofapproximately 318 mcdm-2lx-1.6.3.2 The combined spectral distribution of the illuminationand the spectral responsivity of the receiver shall match thecombined spectral
32、 distribution of CIE Illuminant D65 and theV(l) spectral luminosity function according to the followingcriterion: For any relevant choice of plano parallel coloredabsorptive filter mounted in the path of light to the detector,when measuring a white reflective sample or calibrationstandard, the ratio
33、 of the Qd measured with the filter to the Qdmeasured without the filter shall be within 10 % of theIlluminant D65 luminous transmittance of the filter. See Fig. 2for the position of the absorptive filter. Relevant absorptivefilters shall include at least a yellow filter of color at about theaccepta
34、ble limit toward green and a yellow filter of color atabout the acceptable limit toward red.NOTE 2Absorptive long pass filters with pass wavelengths at about515 nm and 550 nm are commercially available and correspond togreenish yellow and reddish yellow. Illuminant D65 luminous transmit-tance values
35、 must be derived by measurement of the individual filters, buttypical values are given below.Filter Type and Thickness 1 mm 2 mm 3 mm515 nm 0.803 0.777 0.758550 nm n/a n/a 0.4896.3.2.1 If the instrument is intended to be used for materialsof other colors, relevant absorptive filters shall include fi
36、lters ofsuch colors. It is recommended to test also the response toinfrared radiation by means of an infrared absorptive filter, andto request that the Qd measured with the filter is small.NOTE 3Some combinations of light sources and detectors tend to giveresponse to infrared radiation. An absorptiv
37、e long pass filter with passE 2302 03a (2009)2FIG. 1 Illumination System for a Portable Reflectometer: a) Part of a Sphere; b) Bottom Aperture Closed by a Bottom Surface with aSample Gate; c) Bottom Surface with Sample GateFIG. 2 Use of Absorptive Filter and White Reflective Sample or Calibration St
38、andard to Test the Spectral Responsivity of the ReceiverE 2302 03a (2009)3wavelength at about 715 nm is suitable. The Qd measured with the filterinserted should theoretically be zero, but a value from 3 to 3 mcdm-2lx-1is acceptable.6.3.3 The receiver may be either at optical infinity or at afinite d
39、istance from the measurement area, and the co-viewingangle shall be 2.29 6 0.05 as determined from the center ofthe measurement area. See Fig. 3 for a diagram of the opticsgeometry. The co-viewing angle can be tested with lightthrough the aperture stop at the detector, using a frame withpinholes and
40、 targets as shown in Fig. 4. For a non-collimatedinstrument, the pinholes shall be at a location corresponding tothe center of the measurement field.NOTE 4To send light through the aperture stop at the detectorinvolves opening of the reflectometer, which should be done according toinstructions by th
41、e manufacturer of the reflectometer.6.3.4 As determined from the center of the measurementarea, the aperture of the receiver shall not be larger than asquare subtending 20 min of arc (0.33) in both horizontal andvertical directions. For a collimated instrument, the frameshown in Fig. 4 can also be u
42、sed to test the aperture angle,when the targets indicate maximum dimensions.NOTE 5The maximum receiver aperture dimensions are in agreementwith CEN EN 1436.6.3.5 The combined stability of the output of the lightsource and the receiver shall be such that readings will notchange more than 61 % after 1
43、0 s when the reflectometer is incontact with the pavement marking and ready to measure.6.3.6 The linearity of the reflectometer photometric scaleover the range of readings expected shall be within 2 %.Correction factors may be used to ensure a linear response. Amethod for determining linearity is fo
44、und in Annex A2 ofPractice E 809.6.3.7 The reflectometer shall have a zero-adjust control, oran auto-zero function.6.4 Measurement Geometry:6.4.1 The detected area shall either be fully included withinthe illuminated area (called arrangement A) or the illuminatedarea shall be fully included within t
45、he detected area (calledarrangement B).NOTE 6ArrangementAis advantageous to arrangement B in the sensethat it leads to less variation of the measured Qd value with small tilts ofthe reflectometer that are unavoidable in practical field measurements.6.4.2 The smaller of the two areas, detected or ill
46、uminatedarea, is the measurement area and shall be at least 50 cm2. SeeFig. 5 for a method of testing this area.NOTE 7The plate mentioned in Fig. 5 needs in most cases to be aFIG. 3 Optics Geometry Diagram for Portable Reflectometer: a) Angle and Aperture for Non-Collimating Portable Reflectometer;
47、b)Angle and Aperture for Collimating Portable ReflectometerE 2302 03a (2009)4glass plate with a diffuse upper surface, so that the area can be studiedfrom the underside.6.4.3 The larger of the two areas, illuminated or detectedarea, shall be large enough and have spatially uniform charac-teristics (
48、either illumination or sensitivity) such that Qd valuesmeasured on a non-glossy reflective surface shall vary at most610 %, when the height position between surface and reflec-tometer H is changed from 0 mm to 1 mm, 1 mm or 2 mm.This may be performed in the dark. See Fig. 6 for a method oftesting th
49、e variation.NOTE 8Shifts in height positions and tilts of a reflectometer areunavoidable in practical field measurements due to surface texture,particles on the surface, vertical curve of the pavement marking or profile.A reflectometer must have some reserve for practical conditions. Profiledpavement markings require even larger reserves, when profiles are higherthan 2 mm, to be able to measure reliably the Qd values of such pavementmarkings.7. Standardization7.1 The reflectometer shall be standardized using an instru-ment standard consisting of
