1、Designation: E 2302 03aStandard 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 indicates the yea
2、r 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 (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers measurement of the luminanceco
3、efficient 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 reflection of horizont
4、al 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 of the reflectomet
5、er 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 materials onsample pa
6、nels 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 the applica-bility
7、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. Terminology3.1 The
8、 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 illumina-tion, E, at
9、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 (mcdm-2lx-1) providin
10、g 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 measurement ofluminance
11、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 diffuse illumination
12、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.1This test method is under the
13、 jurisdiction of ASTM Committee E12 on Colorand Appearance and is the direct responsibility of Subcommittee E12.10 onRetroreflection.Current edition approved Dec. 1, 2003. Published December 2003. Originallyapproved in 2003. Last previous edition approved in 2003 as E 2302 03.2For referenced ASTM st
14、andards, visit the ASTM website, www.astm.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, Central Secretariat(CEN), ru
15、e de Stassart 36, B1050 Brussels, Belgium.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.4 The portable reflectometer is placed directly over thepavement marking to be measured, ensuring that the measure-ment area of the reflectom
16、eter fits within the width of thestripe, and the reading displayed by the reflectometer isrecorded.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 the stripe for visibil
17、ity 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 viewing,higher levels of
18、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 reflectometer having a ge
19、ometry 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 employ aninstrument h
20、aving 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 the highway pavement
21、 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 signalwhen stray light cou
22、ld 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 Requirements:6.2.1 The i
23、llumination 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 interreflection betweena
24、 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 orby other means. Enough
25、 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 largestmeasurement shall be mi
26、nimum 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 bottomaperture is shown in Fig. 1.
27、 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 notdistort the uniformity o
28、f 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 6.2.3needs onlyto be applied with the sample gate open.6.2.4 The sphere may be approximated by ot
29、her 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 at the sample gate. T
30、he 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 sensitivity and rangeto accomm
31、odate 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 distribution of CIE I
32、lluminant 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 of the Qd measured wi
33、th 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 theacceptable limit toward green
34、 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 must be derived by me
35、asurement 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 filters ofsuch colors. I
36、t is recommended to test also the response toE 2302 03a2infrared 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 absorptive long pass
37、 filter with passwavelength 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 distance from the measurement area, and the co-viewingangl
38、e 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 targets as shown in Fig. 4. For a non-collimatedinstrume
39、nt, 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 the manufacturer of the reflectometer.6.3.4 As determined f
40、rom 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 used to test the aperture angle,when the targets indicate
41、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 6 1 % after 10 s when the reflectometer isin contact with the pavemen
42、t marking and ready to measure.FIG. 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 GateE 2302 03a36.3.6 The linearity of the reflectometer photometric scaleover the range of readi
43、ngs expected shall be within 2 %.Correction factors may be used to ensure a linear response. Amethod for determining linearity is found 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:FIG. 2 Use of Absorptive Fil
44、ter and White Reflective Sample or Calibration Standard to Test the Spectral Responsivity of the ReceiverFIG. 3 Optics Geometry Diagram for Portable Reflectometer: a) Angle and Aperture for Non-Collimating Portable Reflectometer; b)Angle and Aperture for Collimating Portable ReflectometerE 2302 03a4
45、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 the detected area (calledarrangement B).NOTE 6ArrangementAis advantageous to arrangement B in the sensethat it leads to less variation of the
46、 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 illuminatedarea, 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
47、 Fig. 5 needs in most cases to be aglass 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 (either illumination or sensitivity) such t
48、hat Qd valuesmeasured on a non-glossy reflective surface shall vary at most6 10 %, when the height position between surface andreflectometer H is changed from 0 mm to 1 mm, 1 mm or 2mm. This may be performed in the dark. See Fig. 6 for amethod of testing the variation.NOTE 8Shifts in height position
49、s 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 a separate panel or other instru-ment standa
