ASTM D8379/D8379M-21
(Practice)Standard Practice for Evaluating Nighttime Retroreflective Sheeting Effectiveness Using Positive-Contrast Textual Sign Scenario Performance Analysis
Standard Practice for Evaluating Nighttime Retroreflective Sheeting Effectiveness Using Positive-Contrast Textual Sign Scenario Performance Analysis
SIGNIFICANCE AND USE
5.1 Retroreflective sheeting is commonly used to improve the nighttime visibility and legibility of traffic signs under vehicle headlight illumination. This standard provides a procedure for evaluating the nighttime retroreflective performance of sign sheeting used in roadway signing in terms of an overall average performance index for predefined road scenarios.
5.2 A procedure to characterize the relationship between sign luminance supply and driver luminance demand at night without conducting field work helps traffic engineers and transportation agencies responsible for specifying highway construction materials and maintaining roadway safety in making informed decisions about the performance of retroreflective sheeting on the signs. The procedure requires the comprehensive measurement of the retroreflective properties of a sheeting according to Practice E809 over a wide range of angles.
5.3 A variety of retroreflective sheeting is available for use on traffic signs. Coefficients of retroreflection are typically measured for a standard set of angle combinations and are used, in part, to certify conformance to a specification or standard. However, while coefficients of retroreflection on some standard angle sets can provide a general idea about a sheeting’s retroreflectivity and help certify conformance to a standard, a more comprehensive analysis is needed to determine how well a sheeting is expected to serve drivers in general, or in specific use-cases. Drivers of different vehicles viewing a multitude of signs in the real world experience a much more complex set of angular combinations than those captured in the standard angle sets. Furthermore, drivers observe luminance, which is affected by not only the coefficient of retroreflection, but also by headlight illumination, distance from the vehicle to the sign, and light attenuation, among other factors.
5.4 This practice utilizes a set of driver sign viewing scenarios. When combined with the coefficients...
SCOPE
1.1 This practice provides a framework to evaluate retroreflective sheeting performance in nighttime driving conditions without a need for field evaluations through a set of sign viewing scenarios representing common use-cases. The evaluation of performance of a specific sheeting is achieved by comparing the luminance provided by a sheeting to the luminance needed by drivers in each scenario. This comparison is expressed in terms of a “Performance Index,” which is a measure for how well the luminance provided to the driver meets their needs, in each of the scenarios. Comparison of the performance index values for different sheeting allows the user to predict differences in nighttime retroreflective performance when those sheeting are used on installed signs.
1.2 The driver-needs data is based on textual signs (not on symbolic signs) with positive contrast (sign text being brighter than its background), and the headlamp illumination is assumed to be low-beams; therefore, performance index is applicable only to textual signs viewed under low-beam headlamp illumination.
1.3 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The value stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the standard.
1.4 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommenda...
General Information
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation:D8379/D8379M −21
Standard Practice for
Evaluating Nighttime Retroreflective Sheeting Effectiveness
Using Positive-Contrast Textual Sign Scenario Performance
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Analysis
This standard is issued under the fixed designation D8379/D8379M; 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 Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
1.1 This practice provides a framework to evaluate retrore-
Barriers to Trade (TBT) Committee.
flective sheeting performance in nighttime driving conditions
without a need for field evaluations through a set of sign
2. Referenced Documents
viewing scenarios representing common use-cases. The evalu-
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2.1 ASTM Standards:
ation of performance of a specific sheeting is achieved by
B209/B209MSpecification for Aluminum and Aluminum-
comparing the luminance provided by a sheeting to the
Alloy Sheet and Plate
luminanceneededbydriversineachscenario.Thiscomparison
B449Specification for Chromates on Aluminum
is expressed in terms of a “Performance Index,” which is a
D8Terminology Relating to Materials for Roads and Pave-
measure for how well the luminance provided to the driver
ments
meets their needs, in each of the scenarios. Comparison of the
E284Terminology of Appearance
performanceindexvaluesfordifferentsheetingallowstheuser
E808Practice for Describing Retroreflection
to predict differences in nighttime retroreflective performance
E809Practice for Measuring Photometric Characteristics of
when those sheeting are used on installed signs.
Retroreflectors
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1.2 The driver-needs data is based on textual signs (not on
2.2 BSI Standard:
symbolic signs) with positive contrast (sign text being brighter
BS 8408:2005Road Traffic Signs. Testing and Performance
than its background), and the headlamp illumination is as-
of Microprismatic Retroreflective Sheeting Materials.
sumed to be low-beams; therefore, performance index is
Specification (Withdrawn)
applicable only to textual signs viewed under low-beam
3. Terminology
headlamp illumination.
3.1 Definitions—For definitions of technical terms used in
1.3 Units—The values stated in either SI units or inch-
this practice, see Terminologies D8 and E284.
pound units are to be regarded separately as standard. The
value stated in each system may not be exact equivalents;
3.2 Definitions of Terms Specific to This Standard:
therefore,eachsystemshallbeusedindependentlyoftheother.
3.2.1 legibility index, n—a surrogate metric for the size of
Combining values from the two systems may result in noncon-
the image on the retina, expressed in terms of the longitudinal
formance with the standard.
(roadway) distance to the sign divided by the height of the
uppercase alphanumeric on the text.
1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the 3.2.2 legibility range, n—the range of distances to a sign,
responsibility of the user of this standard to establish appro-
expressed longitudinally along the roadway centerline, that are
priate safety, health, and environmental practices and deter- between a legibility index of 40 ft/in. [4.8 m/cm] and 20 ft/in.
mine the applicability of regulatory limitations prior to use.
[2.4 m/cm].
1.5 This international standard was developed in accor-
3.2.3 performance index, n—a measure that approximates a
dance with internationally recognized principles on standard-
sign sheeting’s performance, in terms of luminance observed
ization established in the Decision on Principles for the
by the driver, in a given scenario.
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For referenced ASTM standards, visit the ASTM website, www.astm.org, or
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This practice is under the jurisdiction of ASTM Committee D04 on Road and contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Paving Materials and is the direct responsibility of Subcommittee D04.38 on Standards volume information, refer to the standard’s Document Summary page on
Highway Traffic Control Materials. the ASTM website.
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Current edition approved Nov. 1, 2021. Published December 2021. DOI: Available from British Standards Institution (BSI), 389 Chiswick High Rd.,
10.1520/D8379_D8379M-21. London W4 4AL, U.K., http://www.bsigroup.com.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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