1、Designation: E2832 12Standard Test Method forMeasuring the Coefficient of Retroreflected Luminance ofPavement Markings in a Standard Condition of ContinuousWetting (RL-2)1This standard is issued under the fixed designation E2832; the number immediately following the designation indicates the year of
2、original 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 a measurement of the wetretroreflec
3、tive (RL-2) properties of horizontal pavement mark-ing materials, such as traffic stripes and road surface symbols.A standardized method utilizing a standardized continuouswetting device and a portable retroreflectometer is described toobtain measurements of the wet retroreflective properties ofhori
4、zontal pavement markings.1.2 Retroreflective performance obtained with this test in astandardized condition of continuous wetting does not neces-sarily relate to how markings perform in all conditions ofnatural rain.NOTE 1Test Method E2177 may be used to describe the retroreflec-tive properties of p
5、avement markings in conditions of wetness, such asafter a period of rain.1.3 This test method is suitable for measurements made inthe laboratory and in the field when the necessary controls andprecautions are followed.1.4 This test method specifies the use of external beamretroreflectometers conform
6、ing to Test Method E1710.2Theentrance and observation angles required of the retroreflecto-meter in this test method are commonly referred to as “30meter geometry.”21.5 The test method excludes the effects of rain between thevehicle and the marking.1.6 Results obtained using this test method should
7、not be thesole basis for specifying and assessing the wet retroreflectiveeffectiveness of pavement marking systems. Users shouldcomplement the results of this test method with other evalua-tion results, such as nighttime visual inspections.1.7 The values stated in SI units are to be regarded asstand
8、ard. The values given in parentheses are for informationonly.1.8 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-
9、bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3E177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE965 Test Method for Measuring Pavement Ma
10、crotextureDepth Using a Volumetric TechniqueE1710 Test Method for Measurement of RetroreflectivePavement Marking Materials with CEN-Prescribed Geom-etry Using a Portable RetroreflectometerE2177 Test Method for Measuring the Coefficient of Ret-roreflected Luminance (RL) of Pavement Markings in aStand
11、ard Condition of Wetness3. Terminology3.1 Definitions:3.1.1 coeffcient of retroreflected luminance, RL, ntheratio of the luminance, L, of a projected surface to the normalilluminance, E, at the surface on a plane normal to the incidentlight, expressed in millicandelas per square metre per lux(mcd/m2
12、/lx).3.1.2 conditions of continuous wetting, nthe test conditionwhere the pavement marking specimen is subjected to continu-ously uninterrupted water spray applied uniformly over apavement marking at a defined and controlled rate duringmeasurement.3.1.3 external beam RLretroreflectometers, na paveme
13、ntmarking retroreflectometer that measures the coefficient ofretroreflected luminance, RL, in a measurement area that fallsentirely outside the retroreflectometer.1This test method is under the jurisdiction of ASTM Committee E12 on Colorand Appearance and is the direct responsibility of Subcommittee
14、 E12.10 onRetroreflection.Current edition approved April 1, 2012. Published May 2012. DOI: 10.15/E283212.2Reference Test Method E1710. The standard measurement condition is in-tended to represent the angles corresponding to a distance of 30 m for the driver ofa passenger car with an eye height of 1.
15、2 m and a headlight height of 0.65 m abovethe road. See Annex A1.3For referenced ASTM standards, 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 webs
16、ite.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.4 RL-2, nthe steady state coefficient of retroreflectedluminance, RL, determined under defined conditions of con-tinuous wetting at a rate of 2 inches per hour.3.1.4.1 Discussio
17、nThe results from this test method shallbe reported as R(L-2) where “2” designates the wetting rate usedin inches per hour (in./h).3.1.5 steady state conditions, nthe measurements havereached steady state when six consecutive retroreflectometerinstrument readings made at approximately 10 s intervals
18、 showno consistent tending of the coefficient of retroreflected lumi-nance value up or down.4. Summary of Test Method4.1 This test method describes a standard procedure formeasuring the retroreflective properties of horizontally appliedpavement marking systems under conditions of continuouswetting.4
19、.2 The pavement marking system under test is subjected tocontinuous wetting delivered by a wetting device of a specifieddesign calibrated to provide a controlled wetting rate.4.3 A protocol and instrument requirements are describedfor measuring RL-2under a defined condition of continuouswetting.5. S
20、ignificance and Use5.1 This test method produces a measure of retroreflectiveefficiency (coefficient of retroreflected luminance, RL-2) for apavement marking system under conditions of continuouswetting. The test result depends on factors such as thepavement marking binder and optic materials, their
21、 application,wear from traffic and plowing, wetting rate, and road grade andcross slope.5.2 The measured retroreflective efficiency under conditionsof continuous wetting may be used to characterize the proper-ties of a pavement marking on the road as water is continuouslyfalling on it. The retrorefl
22、ective efficiency of the marking underconditions of continuous wetting is almost always differentthan under dry conditions.5.3 The wetting rate of 2 in./h represents the upper limit ofwhat is meteorologically classified as heavy rainfall. Rainfallrates above 2 in./h are classified as extreme or viol
23、ent, and aresometimes associated with weather such as tropical storms.5.4 The retroreflectivity of pavement markings degradeswith traffic wear and requires periodic measurement to ensurethat the coefficient of retroreflected luminance under continu-ous wetting meets requirements and provides adequat
24、e visibil-ity for nighttime drivers.5.5 The continuous wetting rate as well as the roadwaygrade and cross slope impact the results of this test method.The user shall measure and report the rate used for testing.5.6 The roadway grade and cross slope adjacent to themeasurement area impact the results
25、of this test method. Adigital level (inclinometer) can be used to quickly measuregrade and cross slope.5.7 Results obtained using this test method should not be thesole basis for specifying and assessing the wet retroreflectiveeffectiveness of pavement marking systems. Users shouldcomplement the res
26、ults of this test method with other evalua-tion results, such as nighttime visual inspections.6. Interferences6.1 Newly installed pavement markings may have surfaceproperties that prevent uniform wetting. This hydrophobiccondition can produce inconsistent and highly variable resultswhen measuring th
27、e coefficient of retroreflected luminanceunder continuous wetting conditions.6.1.1 It is recommended that measurements be made at least14 days after markings are applied. Hydrophobic conditionsare generally eliminated by exposure to the environment andwear of traffic.6.1.2 For laboratory measurement
28、s of pavement markingsystems installed on panels, particular care must be taken toavoid hydrophobic conditions, since the panels are typicallynot exposed to traffic. The use of a surfactant in the waterreservoir has created problems of microscopic foaming andbubbles, resulting in unacceptable variab
29、ility in readings. Moretesting is needed before a specific surfactant can be recom-mended.7. Apparatus7.1 Retroreflectometer:7.1.1 The retroreflectometer shall be an external beam RLretroreflectometer (see 3.1.3).7.1.2 The retroreflectometer shall have such dimensions andlocation of the measurement
30、area such that the retroreflecto-meter can be placed relative to the wetting device so that themeasurement area falls entirely within the wetted area insidethe wetting device.7.1.3 The retroreflectometer shall meet the requirements ofTest Method E1710.7.2 Wetting Device:7.2.1 The wetting device shal
31、l conform to the design andoperating parameters in Annex A1.NOTE 2Water drop size and velocity at impact will impact retrore-flected luminance measurements of markings. The wetting apparatusdescribed in Annex A1 has particular water impact characteristics thathave not been quantified. In order to me
32、asure the retroreflected luminancemeasurements of markings under conditions of continuous wetting in astandard way, the design and construction of the wetting device describedin Annex A1 must be followed.8. Reagents and Materials8.1 Clean water free of particulate and dissolved solids shallbe used t
33、o prevent clogging of the nozzles. Commercialdistilled drinking water is recommended.9. Sampling, Test Specimens, and Test Units9.1 For field measurements, the test specimens selectedshall be visually representative of the pavement marking to beevaluated and free of obvious excessive wear such as sk
34、idmarks or plow damage.9.2 Although only one test specimen is required, multipletest specimens are recommended.9.3 Measurements shall be recorded only after steady stateconditions have been achieved. Record a minimum of fourinstrument readings before moving the wetting apparatus.10. Calibration and
35、Standardization10.1 External Beam Retroreflectometer:E2832 12210.1.1 The retroreflectometer shall be standardized accord-ing to the instructions from the instrument manufacturer usingthe calibrated reference or working standard supplied with theinstrument.10.1.2 Transporting portable retroreflectome
36、ters from an airconditioned area to the test site may result in fogging of mirrorsin the instrument. If there is any doubt concerning thestandardization or if the readings of the reference or workingstandard are not constant, allow the instrument to reachambient conditions and re-standardize with th
37、e reference orworking standard. If the problem persists, suspend the mea-surements until the instrument can be repaired.10.1.3 The standardization of the instrument shall be re-verified at least once per day under dry conditions. If thesubsequent readings on the reference standard deviate by moretha
38、n five percent from the reference value, re-standardizationshall be performed. If the readings on the reference standarddeviate by more than ten percent from the reference value,re-standardize and, in addition, repeat all measurements madesubsequent to the prior successful verification or standardiz
39、a-tion.10.2 Wetting Device:10.2.1 Calibration of the wetting rate shall be performedprior to any measurements. Adjust the nozzle angle andoperating pressure until the required continuous wetting rate isachieved.10.2.2 Center three adjacently placed dry containers ofknown opening area (each measuring
40、 approximately 100 mm(4 in.) wide by 100 mm (4 in.) long) over the retroreflectometermeasurement area (the containers shall be at least 12.5 mm (0.5in.) deep). Turn on the wetting device and collect water for atleast two minutes. Determine the volume of water using one ofthe following procedures.10.
41、2.2.1 Volumetric MethodPour the contents of eachcontainer into a dry 50 mL graduated cylinder. Record thevolume of water collected to the nearest 0.1 mL in eachindividual container. Divide the volume of water by thecollection time in minutes. Record the volume per minute inmL/min.10.2.2.2 Gravimetri
42、c MethodPrior to the calibration,weigh each dry container and record its tare weight to thenearest 0.1 g. After collecting the water spray, reweigh andrecord the gross weight of each container. Calculate the netweight of water collected by subtracting the tare weight fromthe gross weight. Divide the
43、 net weight of water collected ineach container by the density of water (1.0 g/mL) to obtain thevolume of water collected in each container. Divide the volumeof water by the collection time in minutes. Record the volumeper minute in mL/min.10.2.3 Wetting Rate CalculationCalculate the wetting ratefor
44、 each container from Eq 1. The required wetting rate is 2.06 0.2 in./h.Wetting Rate in./h! 5 VPM/Area!*0.394 in./cm!*60 min./h! (1)where:VPM = volume per minute, in mL/min; andArea = container opening area, in cm2.10.2.4 To check the spray pattern for uniformity across themeasurement area, compare w
45、etting rates calculated for thethree containers. The wetting rates measured for each indi-vidual container shall be within 20 percent of the averagewetting rate of the three containers.10.2.5 The wetting rate and uniformity of spray shall bechecked regularly. It is recommended that the wetting rate
46、anduniformity of spray should be verified at least daily and priorto taking measurements. If the spray pattern or wetting ratechanges, check the nozzles for debris that may have accumu-lated. The nozzles shall be cleaned and the wetting raterechecked. A visual inspection of the spray pattern can beh
47、elpful to identify non-uniform spray and the need to clean thenozzles.10.2.6 A light trap shall be installed opposite the retrore-flectometer opening to reduce stray light from positivelybiasing the measurement. To determine if the light trap isfunctioning as desired, position the retroreflectometer
48、 andwetting apparatus over a flat pavement surface without retrore-flective markings. Once the pavement surface is saturated andwhile the wetting device is operating at the desired wettingrate, record a reading. The reading must be less than 5mcd/lx/m2when no retroreflective marking is present.11. P
49、rocedure11.1 Measure the grade and cross slope of the pavementadjacent to the test specimen.11.1.1 Measurements in the field shall not be made whereboth the cross slope and grade are less than 0.5 percent, orwhere the water submerges the test specimen.11.1.2 Measurements in the laboratory shall be made withthe test specimen resting on a two percent cross slope and a onepercent grade.11.2 Place the wetting device on the test specimen makingsure that the wetting area is aligned with the test specimen.11.3 Turn on the wetting device pump, check the pressure,and verify th
