ASTM E2832-12
(Test Method)Standard Test Method for Measuring the Coefficient of Retroreflected Luminance of Pavement Markings in a Standard Condition of Continuous Wetting (RL-2)
Standard Test Method for Measuring the Coefficient of Retroreflected Luminance of Pavement Markings in a Standard Condition of Continuous Wetting (R<inf>L-2</inf>)
SIGNIFICANCE AND USE
This test method produces a measure of retroreflective efficiency (coefficient of retroreflected luminance, RL-2) for a pavement marking system under conditions of continuous wetting. The test result depends on factors such as the pavement marking binder and optic materials, their application, wear from traffic and plowing, wetting rate, and road grade and cross slope.
The measured retroreflective efficiency under conditions of continuous wetting may be used to characterize the properties of a pavement marking on the road as water is continuously falling on it. The retroreflective efficiency of the marking under conditions of continuous wetting is almost always different than under dry conditions.
The wetting rate of 2 in./h represents the upper limit of what is meteorologically classified as heavy rainfall. Rainfall rates above 2 in./h are classified as extreme or violent, and are sometimes associated with weather such as tropical storms.
The retroreflectivity of pavement markings degrades with traffic wear and requires periodic measurement to ensure that the coefficient of retroreflected luminance under continuous wetting meets requirements and provides adequate visibility for nighttime drivers.
The continuous wetting rate as well as the roadway grade and cross slope impact the results of this test method. The user shall measure and report the rate used for testing.
The roadway grade and cross slope adjacent to the measurement area impact the results of this test method. A digital level (inclinometer) can be used to quickly measure grade and cross slope.
Results obtained using this test method should not be the sole basis for specifying and assessing the wet retroreflective effectiveness of pavement marking systems. Users should complement the results of this test method with other evaluation results, such as nighttime visual inspections.
SCOPE
1.1 This test method covers a measurement of the wet retroreflective (RL-2) properties of horizontal pavement marking materials, such as traffic stripes and road surface symbols. A standardized method utilizing a standardized continuous wetting device and a portable retroreflectometer is described to obtain measurements of the wet retroreflective properties of horizontal pavement markings.
1.2 Retroreflective performance obtained with this test in a standardized condition of continuous wetting does not necessarily relate to how markings perform in all conditions of natural rain.
Note 1—Test Method E2177 may be used to describe the retroreflective properties of pavement markings in conditions of wetness, such as after a period of rain.
1.3 This test method is suitable for measurements made in the laboratory and in the field when the necessary controls and precautions are followed.
1.4 This test method specifies the use of external beam retroreflectometers conforming to Test Method E1710. The entrance and observation angles required of the retroreflectometer in this test method are commonly referred to as “30 meter geometry.”
1.5 The test method excludes the effects of rain between the vehicle and the marking.
1.6 Results obtained using this test method should not be the sole basis for specifying and assessing the wet retroreflective effectiveness of pavement marking systems. Users should complement the results of this test method with other evaluation results, such as nighttime visual inspections.
1.7 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.
1.8 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 and health practices and determine the applicability of regulatory limitations prior to use.
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Designation:E2832 −12
Standard Test Method for
Measuring the Coefficient of Retroreflected Luminance of
Pavement Markings in a Standard Condition of Continuous
Wetting (R )
L-2
This standard is issued under the fixed designation E2832; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.7 The values stated in SI units are to be regarded as
standard. The values given in parentheses are for information
1.1 This test method covers a measurement of the wet
only.
retroreflective (R ) properties of horizontal pavement mark-
L-2
1.8 This standard does not purport to address all of the
ing materials, such as traffic stripes and road surface symbols.
safety concerns, if any, associated with its use. It is the
A standardized method utilizing a standardized continuous
responsibility of the user of this standard to establish appro-
wetting device and a portable retroreflectometer is described to
priate safety and health practices and determine the applica-
obtain measurements of the wet retroreflective properties of
bility of regulatory limitations prior to use.
horizontal pavement markings.
1.2 Retroreflective performance obtained with this test in a
2. Referenced Documents
standardized condition of continuous wetting does not neces-
2.1 ASTM Standards:
sarily relate to how markings perform in all conditions of
E177 Practice for Use of the Terms Precision and Bias in
natural rain.
ASTM Test Methods
NOTE 1—Test Method E2177 may be used to describe the retroreflec-
E691 Practice for Conducting an Interlaboratory Study to
tive properties of pavement markings in conditions of wetness, such as
after a period of rain. Determine the Precision of a Test Method
E965 Test Method for Measuring Pavement Macrotexture
1.3 This test method is suitable for measurements made in
Depth Using a Volumetric Technique
the laboratory and in the field when the necessary controls and
E1710 Test Method for Measurement of Retroreflective
precautions are followed.
Pavement Marking Materials with CEN-Prescribed Ge-
1.4 This test method specifies the use of external beam
ometry Using a Portable Retroreflectometer
retroreflectometers conforming to Test Method E1710. The
E2177 Test Method for Measuring the Coefficient of Ret-
entrance and observation angles required of the retroreflecto-
roreflected Luminance (R ) of Pavement Markings in a
L
meter in this test method are commonly referred to as “30
Standard Condition of Wetness
meter geometry.”
3. Terminology
1.5 The test method excludes the effects of rain between the
3.1 Definitions:
vehicle and the marking.
3.1.1 coeffıcient of retroreflected luminance, R ,n—the ratio
L
1.6 Resultsobtainedusingthistestmethodshouldnotbethe
of the luminance, L, of a projected surface to the normal
sole basis for specifying and assessing the wet retroreflective
illuminance, E, at the surface on a plane normal to the incident
effectiveness of pavement marking systems. Users should
light, expressed in millicandelas per square metre per lux
complement the results of this test method with other evalua-
(mcd/m /lx).
tion results, such as nighttime visual inspections.
3.1.2 conditions of continuous wetting, n—the test condition
where the pavement marking specimen is subjected to continu-
ously uninterrupted water spray applied uniformly over a
This test method is under the jurisdiction of ASTM Committee E12 on Color
pavement marking at a defined and controlled rate during
and Appearance and is the direct responsibility of Subcommittee E12.10 on
measurement.
Retroreflection.
Current edition approved April 1, 2012. Published May 2012. DOI: 10.15/
E2832–12.
2 3
Reference Test Method E1710. The standard measurement condition is in- For referenced ASTM standards, visit the ASTM website, www.astm.org, or
tended to represent the angles corresponding to a distance of 30 m for the driver of contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
a passenger car with an eye height of 1.2 m and a headlight height of 0.65 m above Standards volume information, refer to the standard’s Document Summary page on
the road. See Annex A1. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2832−12
3.1.3 external beam R retroreflectometers, n—a pavement digital level (inclinometer) can be used to quickly measure
L
marking retroreflectometer that measures the coefficient of grade and cross slope.
retroreflected luminance, R , in a measurement area that falls
L
5.7 Resultsobtainedusingthistestmethodshouldnotbethe
entirely outside the retroreflectometer.
sole basis for specifying and assessing the wet retroreflective
3.1.4 R ,n—the steady state coefficient of retroreflected
effectiveness of pavement marking systems. Users should
L-2
luminance, R , determined under defined conditions of con-
complement the results of this test method with other evalua-
L
tinuous wetting at a rate of 2 inches per hour.
tion results, such as nighttime visual inspections.
3.1.4.1 Discussion—The results from this test method shall
6. Interferences
bereportedas R( )where“2”designatesthewettingrateused
L-2
in inches per hour (in./h). 6.1 Newly installed pavement markings may have surface
properties that prevent uniform wetting. This hydrophobic
3.1.5 steady state conditions, n—the measurements have
condition can produce inconsistent and highly variable results
reached steady state when six consecutive retroreflectometer
when measuring the coefficient of retroreflected luminance
instrument readings made at approximately 10 s intervals show
under continuous wetting conditions.
no consistent tending of the coefficient of retroreflected lumi-
6.1.1 It is recommended that measurements be made at least
nance value up or down.
14 days after markings are applied. Hydrophobic conditions
4. Summary of Test Method
are generally eliminated by exposure to the environment and
wear of traffic.
4.1 This test method describes a standard procedure for
6.1.2 For laboratory measurements of pavement marking
measuring the retroreflective properties of horizontally applied
systems installed on panels, particular care must be taken to
pavement marking systems under conditions of continuous
avoid hydrophobic conditions, since the panels are typically
wetting.
not exposed to traffic. The use of a surfactant in the water
4.2 The pavement marking system under test is subjected to
reservoir has created problems of microscopic foaming and
continuous wetting delivered by a wetting device of a specified
bubbles,resultinginunacceptablevariabilityinreadings.More
design calibrated to provide a controlled wetting rate.
testing is needed before a specific surfactant can be recom-
4.3 A protocol and instrument requirements are described
mended.
for measuring R under a defined condition of continuous
L-2
7. Apparatus
wetting.
7.1 Retroreflectometer:
5. Significance and Use
7.1.1 The retroreflectometer shall be an external beam R
L
5.1 This test method produces a measure of retroreflective
retroreflectometer (see 3.1.3).
efficiency (coefficient of retroreflected luminance, R ) for a
7.1.2 The retroreflectometer shall have such dimensions and
L-2
pavement marking system under conditions of continuous
location of the measurement area such that the retroreflecto-
wetting. The test result depends on factors such as the
meter can be placed relative to the wetting device so that the
pavementmarkingbinderandopticmaterials,theirapplication,
measurement area falls entirely within the wetted area inside
wear from traffic and plowing, wetting rate, and road grade and
the wetting device.
cross slope.
7.1.3 The retroreflectometer shall meet the requirements of
Test Method E1710.
5.2 The measured retroreflective efficiency under conditions
of continuous wetting may be used to characterize the proper-
7.2 Wetting Device:
tiesofapavementmarkingontheroadaswateriscontinuously
7.2.1 The wetting device shall conform to the design and
fallingonit.Theretroreflectiveefficiencyofthemarkingunder
operating parameters in Annex A1.
conditions of continuous wetting is almost always different
NOTE 2—Water drop size and velocity at impact will impact retrore-
than under dry conditions.
flected luminance measurements of markings. The wetting apparatus
described in Annex A1 has particular water impact characteristics that
5.3 The wetting rate of 2 in./h represents the upper limit of
have not been quantified. In order to measure the retroreflected luminance
what is meteorologically classified as heavy rainfall. Rainfall
measurements of markings under conditions of continuous wetting in a
rates above 2 in./h are classified as extreme or violent, and are
standard way, the design and construction of the wetting device described
sometimes associated with weather such as tropical storms.
in Annex A1 must be followed.
5.4 The retroreflectivity of pavement markings degrades
8. Reagents and Materials
with traffic wear and requires periodic measurement to ensure
8.1 Cleanwaterfreeofparticulateanddissolvedsolidsshall
that the coefficient of retroreflected luminance under continu-
be used to prevent clogging of the nozzles. Commercial
ous wetting meets requirements and provides adequate visibil-
distilled drinking water is recommended.
ity for nighttime drivers.
5.5 The continuous wetting rate as well as the roadway 9. Sampling, Test Specimens, and Test Units
grade and cross slope impact the results of this test method.
9.1 For field measurements, the test specimens selected
The user shall measure and report the rate used for testing.
shall be visually representative of the pavement marking to be
5.6 The roadway grade and cross slope adjacent to the evaluated and free of obvious excessive wear such as skid
measurement area impact the results of this test method. A marks or plow damage.
E2832−12
9.2 Although only one test specimen is required, multiple 10.2.3 Wetting Rate Calculation—Calculate the wetting rate
test specimens are recommended. for each container from Eq 1. The required wetting rate is 2.0
6 0.2 in./h.
9.3 Measurements shall be recorded only after steady state
Wetting Rate in./h 5 VPM/Area *0.394 in./cm *60 min./h (1)
~ ! ~ ! ~ ! ~ !
conditions have been achieved. Record a minimum of four
instrument readings before moving the wetting apparatus.
where:
VPM = volume per minute, in mL/min; and
10. Calibration and Standardization
Area = container opening area, in cm .
10.1 External Beam Retroreflectometer:
10.2.4 To check the spray pattern for uniformity across the
10.1.1 The retroreflectometer shall be standardized accord-
measurement area, compare wetting rates calculated for the
ing to the instructions from the instrument manufacturer using
three containers. The wetting rates measured for each indi-
the calibrated reference or working standard supplied with the
vidual container shall be within 20 percent of the average
instrument.
wetting rate of the three containers.
10.1.2 Transporting portable retroreflectometers from an air
10.2.5 The wetting rate and uniformity of spray shall be
conditionedareatothetestsitemayresultinfoggingofmirrors
checked regularly. It is recommended that the wetting rate and
in the instrument. If there is any doubt concerning the
uniformity of spray should be verified at least daily and prior
standardization or if the readings of the reference or working
to taking measurements. If the spray pattern or wetting rate
standard are not constant, allow the instrument to reach
changes, check the nozzles for debris that may have accumu-
ambient conditions and re-standardize with the reference or
lated. The nozzles shall be cleaned and the wetting rate
working standard. If the problem persists, suspend the mea-
rechecked. A visual inspection of the spray pattern can be
surements until the instrument can be repaired.
helpful to identify non-uniform spray and the need to clean the
10.1.3 The standardization of the instrument shall be re-
nozzles.
verified at least once per day under dry conditions. If the
10.2.6 A light trap shall be installed opposite the retrore-
subsequent readings on the reference standard deviate by more
flectometer opening to reduce stray light from positively
than five percent from the reference value, re-standardization
biasing the measurement. To determine if the light trap is
shall be performed. If the readings on the reference standard
functioning as desired, position the retroreflectometer and
deviate by more than ten percent from the reference value,
wetting apparatus over a flat pavement surface without retrore-
re-standardize and, in addition, repeat all measurements made
flective markings. Once the pavement surface is saturated and
subsequent to the prior successful verification or standardiza-
while the wetting device is operating at the desired wetting
tion.
rate, record a reading. The reading must be less than 5
mcd/lx/m when no retroreflective marking is present.
10.2 Wetting Device:
10.2.1 Calibration of the wetting rate shall be performed
11. Procedure
prior to any measurements. Adjust the nozzle angle and
11.1 Measure the grade and cross slope of the pavement
operating pressure until the required continuous wetting rate is
adjacent to the test specimen.
achieved.
11.1.1 Measurements in the field shall not be made where
10.2.2 Center three adjacently placed dry containers of
both the cross slope and grade are less than 0.5 percent, or
known opening area (each measuring approximately 100 mm
where the water submerges the test specimen.
(4in.)wideby100mm(4in.)long)overtheretroreflectometer
11.1.2 Measurements in the laboratory shall be made with
measurementarea(thecontainersshallbeatleast12.5mm(0.5
thetestspecimenrestingonatwopercentcrossslopeandaone
in.) deep). Turn on the wetting device and collect water for at
percent grade.
least two minutes. Determine the volume of water using one of
the following procedures.
11.2 Place the wetting device on the test specimen making
10.2.2.1 Volumetric Method—Pour the contents of each sure that the wetting area is aligned with the test specimen.
container into a dry 50 mL graduated cylinder. Record the
11.3 Turn on the wetting device pump, check the pressure,
volume of water collected to the nearest 0.1 mL in each
and verify that the test specimen is being uniformly wetted at
individual container. Divide the volume of water by the
a rate of 2.0 6 0.2 in./h.
collection time in minutes. Record the volume per minute in
11.4 With the wetting device in position, gently place t
...
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