1、Designation: E2832 12 (Reapproved 2017)Standard 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 ind
2、icates 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 a measurement of
3、the wetretroreflective (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
4、 properties ofhorizontal 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-ti
5、ve properties of pavement 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 beamretrorefl
6、ectometers conforming 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 t
7、est method should 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 b
8、e regarded asstandard. 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, health, and environmental pr
9、actices and deter-mine the applicability of regulatory limitations prior to use.1.9 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides
10、and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.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 o
11、f a Test MethodE965 Test Method for Measuring Pavement MacrotextureDepth Using a Volumetric TechniqueE1710 Test Method for Measurement of RetroreflectivePavement Marking Materials with CEN-Prescribed Ge-ometry Using a Portable RetroreflectometerE2177 Test Method for Measuring the Coefficient of Ret-
12、roreflected Luminance (RL) of Pavement Markings in aStandard Condition of Wetness3. Terminology3.1 Definitions:3.1.1 coeffcient of retroreflected luminance, RL,nthe ratioof the luminance, L, of a projected surface to the normalilluminance, E, at the surface on a plane normal to the incidentlight, ex
13、pressed in millicandelas per square metre per lux(mcd/m2/lx).1This test method is under the jurisdiction of ASTM Committee E12 on Colorand Appearance and is the direct responsibility of Subcommittee E12.10 onRetroreflection.Current edition approved Nov. 1, 2017. Published November 2017. Originallyap
14、proved in 2012. Last previous edition approved in 2012 as E2832 12. DOI:10.15/E2832-12R17.2Reference 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 1.2 m and a headl
15、ight 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 website.Copyright A
16、STM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International St
17、andards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.13.1.2 conditions of continuous wetting, nthe test conditionwhere the pavement marking specimen is subjected to continu-ously uninterrupted water spray applied uniformly over apavem
18、ent marking at a defined and controlled rate duringmeasurement.3.1.3 external beam RLretroreflectometers, na pavementmarking retroreflectometer that measures the coefficient ofretroreflected luminance, RL, in a measurement area that fallsentirely outside the retroreflectometer.3.1.4 RL-2,nthe steady
19、 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 DiscussionThe 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 stead
20、y state conditions, nthe measurements havereached steady state when six consecutive retroreflectometerinstrument readings made at approximately 10 s intervals showno consistent tending of the coefficient of retroreflected lumi-nance value up or down.4. Summary of Test Method4.1 This test method desc
21、ribes a standard procedure formeasuring the retroreflective properties of horizontally appliedpavement marking systems under conditions of continuouswetting.4.2 The pavement marking system under test is subjected tocontinuous wetting delivered by a wetting device of a specifieddesign calibrated to p
22、rovide a controlled wetting rate.4.3 A protocol and instrument requirements are describedfor measuring RL-2under a defined condition of continuouswetting.5. Significance and Use5.1 This test method produces a measure of retroreflectiveefficiency (coefficient of retroreflected luminance, RL-2) for ap
23、avement marking system under conditions of continuouswetting. The test result depends on factors such as thepavement marking binder and optic materials, their application,wear from traffic and plowing, wetting rate, and road grade andcross slope.5.2 The measured retroreflective efficiency under cond
24、itionsof continuous wetting may be used to characterize the proper-ties of a pavement marking on the road as water is continuouslyfalling on it. The retroreflective efficiency of the marking underconditions of continuous wetting is almost always differentthan under dry conditions.5.3 The wetting rat
25、e 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 violent, and aresometimes associated with weather such as tropical storms.5.4 The retroreflectivity of pavement markings degradeswith traffic wear
26、 and requires periodic measurement to ensurethat the coefficient of retroreflected luminance under continu-ous wetting meets requirements and provides adequate visibil-ity for nighttime drivers.5.5 The continuous wetting rate as well as the roadwaygrade and cross slope impact the results of this tes
27、t 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 of this test method. Adigital level (inclinometer) can be used to quickly measuregrade and cross slope.5.7 Results obtained using this test me
28、thod should 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.6. Interferences6.1 Newly installed pavement mar
29、kings may have surfaceproperties that prevent uniform wetting. This hydrophobiccondition can produce inconsistent and highly variable resultswhen measuring the coefficient of retroreflected luminanceunder continuous wetting conditions.6.1.1 It is recommended that measurements be made at least14 days
30、 after markings are applied. Hydrophobic conditionsare generally eliminated by exposure to the environment andwear of traffic.6.1.2 For laboratory measurements of pavement markingsystems installed on panels, particular care must be taken toavoid hydrophobic conditions, since the panels are typically
31、not exposed to traffic. The use of a surfactant in the waterreservoir has created problems of microscopic foaming andbubbles, resulting in unacceptable variability in readings. Moretesting is needed before a specific surfactant can be recom-mended.7. Apparatus7.1 Retroreflectometer:7.1.1 The retrore
32、flectometer shall be an external beam RLretroreflectometer (see 3.1.3).7.1.2 The retroreflectometer shall have such dimensions andlocation of the measurement area such that the retroreflecto-meter can be placed relative to the wetting device so that themeasurement area falls entirely within the wett
33、ed 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 shall conform to the design andoperating parameters in Annex A1.NOTE 2Water drop size and velocity at impact will impact retrore-flected luminance
34、 measurements of markings. The wetting apparatusdescribed in Annex A1 has particular water impact characteristics thathave not been quantified. In order to measure the retroreflected luminancemeasurements of markings under conditions of continuous wetting in astandard way, the design and constructio
35、n 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 to prevent clogging of the nozzles. Commercialdistilled drinking water is recommended.E2832 12 (2017)29. Sampling, Test Specimens, and Test Uni
36、ts9.1 For field measurements, the test specimens selectedshall be visually representative of the pavement marking to beevaluated and free of obvious excessive wear such as skidmarks or plow damage.9.2 Although only one test specimen is required, multipletest specimens are recommended.9.3 Measurement
37、s shall be recorded only after steady stateconditions have been achieved. Record a minimum of fourinstrument readings before moving the wetting apparatus.10. Calibration and Standardization10.1 External Beam Retroreflectometer:10.1.1 The retroreflectometer shall be standardized accord-ing to the ins
38、tructions from the instrument manufacturer usingthe calibrated reference or working standard supplied with theinstrument.10.1.2 Transporting portable retroreflectometers from an airconditioned area to the test site may result in fogging of mirrorsin the instrument. If there is any doubt concerning t
39、hestandardization or if the readings of the reference or workingstandard are not constant, allow the instrument to reachambient conditions and re-standardize with the reference orworking standard. If the problem persists, suspend the mea-surements until the instrument can be repaired.10.1.3 The stan
40、dardization of the instrument shall be re-verified at least once per day under dry conditions. If thesubsequent readings on the reference standard deviate by morethan five percent from the reference value, re-standardizationshall be performed. If the readings on the reference standarddeviate by more
41、 than ten percent from the reference value,re-standardize and, in addition, repeat all measurements madesubsequent to the prior successful verification or standardiza-tion.10.2 Wetting Device:10.2.1 Calibration of the wetting rate shall be performedprior to any measurements. Adjust the nozzle angle
42、andoperating pressure until the required continuous wetting rate isachieved.10.2.2 Center three adjacently placed dry containers ofknown opening area (each measuring approximately 100 mm(4 in.) wide by 100 mm (4 in.) long) over the retroreflectometermeasurement area (the containers shall be at least
43、 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.10.2.2.1 Volumetric MethodPour the contents of eachcontainer into a dry 50 mL graduated cylinder. Record thevolume of water collected to t
44、he 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 Gravimetric MethodPrior to the calibration,weigh each dry container and record its tare weight to thenearest 0.1 g. After collecting the water sp
45、ray, reweigh andrecord the gross weight of each container. Calculate the netweight of water collected by subtracting the tare weight fromthe gross weight. Divide the net weight of water collected ineach container by the density of water (1.0 g/mL) to obtain thevolume of water collected in each conta
46、iner. 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 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)wher
47、e: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 wetting rates calculated for thethree containers. The wetting rates measured for each indi-vidual container shall be within 20 percent o
48、f 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 anduniformity of spray should be verified at least daily and priorto taking measurements. If the spray pattern or wetting ratechanges,
49、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 behelpful 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 andwetting apparatus over a flat pavement surface without retrore-flective markings. Once the pavement surf
