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D4956-19 – Standard Test Method Technical Guide
📐 Specification Scope and Sheeting Types
This specification covers flexible, non-exposed glass-bead lens and microprismatic, retroreflective sheeting designed for use on traffic control signs, delineators, barricades, and other devices. This specification does not address inks, overlays, or other imaging methods that may be applied to retroreflective sheeting material to create traffic signs or other devices. Although this specification provides photometric requirements for retroreflective sheeting under evaluation, minimum performance requirements of in-service signs or other devices are outside the scope of this document. The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.
⚙️ Test Methods and Procedures
This standard references several ASTM standards for testing retroreflective sheeting. The following table lists key test methods used for evaluating photometric and colorimetric properties.
| 🟦 Standard | 📏 Application |
|---|---|
| E810 | Test Method for Coefficient of Retroreflection of Retroreflective Sheeting Using Coplanar Geometry |
| E811 | Practice for Measuring Colorimetric Characteristics of Retroreflectors Under Nighttime Conditions |
| E308 | Practice for Computing the Colors of Objects Using the CIE System |
| E1349 | Test Method for Reflectance Factor and Color by Spectrophotometry Using Bidirectional Geometry |
| E2301 | Test Method for Daytime Colorimetric Properties of Fluorescent Retroreflective Sheeting |
| E3165 | Test Method for Nighttime Retroreflected Chromaticity of Retroreflective Sheeting |
📊 Key Measured Properties
The standard specifies photometric requirements for retroreflective sheeting, including coefficient of retroreflection measured per E810, and colorimetric properties for daytime and nighttime conditions. Nighttime retroreflected chromaticity is measured per E3165, and daytime color is evaluated using methods like E1349 or E2301. The standard also references practices for environmental exposure testing per G7/G7M and terminology from E284 and G113. It is the responsibility of the user to establish safety, health, and environmental practices.
💡 Tip: The standard uses inch-pound units as primary. Ensure conversions to SI units are treated as supplementary.
✅ Note: This standard has been approved for use by agencies of the U.S. Department of Defense.
❓ Frequently Asked Questions
🔍 What types of retroreflective sheeting are covered by D4956-19?
The standard covers flexible, non-exposed glass-bead lens and microprismatic retroreflective sheeting for traffic control devices.
💡 Does this standard address imaging methods or in-service performance?
No, it does not address inks, overlays, or imaging methods, and in-service sign performance is outside its scope.
⚡ What are the key test methods referenced for retroreflection and color?
Key methods include E810 for coefficient of retroreflection, E811 for nighttime color, and E1349 for daytime color measurement.
📌 What safety precautions are mentioned in the standard?
The standard includes a safety hazards caveat for the test methods section, emphasizing the user’s responsibility to establish safety practices.