ASTM E811-09 (2025) PDF

Full title and description

Standard Practice for Measuring Colorimetric Characteristics of Retroreflectors Under Nighttime Conditions — ASTM E811-09, reapproved/reaffirmed in subsequent review cycles (listed as E811-09(2025) in current catalogs). This practice defines procedures for instrumental determination of retroreflected chromaticity coordinates of retroreflective materials and sign faces when viewed under nighttime (retroreflective) illumination geometries using telecolorimeters or telespectroradiometers.

Abstract

This practice describes measurement techniques and calculation methods to quantify the chromaticity (colorimetric) appearance of retroreflective materials as seen under typical vehicle headlamp illumination and driver observation geometries. It specifies test arrangement, reference illuminant (CIE Standard Source A), instrumentation options, and references related practices for geometry and chromaticity computation to ensure repeatable, comparable nighttime color measurements of retroreflectors.

General information

• Status: Active (reapproved/reissued in catalog listings as E811-09(2025)).
• Publication date: Original designation E811-09 — published January 12, 2009; current catalog entry/reapproval shown for 2025 (listed as E811-09(2025)).
• Publisher: ASTM International (Committee E12, Subcommittee E12.10 — Image and appearance).
• ICS / categories: 93.080.30 (Road equipment and installations), appearance and colorimetry categories.
• Edition / version: E811-09 (with reapproval/reissue entries shown as E811-09(2015), E811-09(2020)e1 and cataloged as E811-09(2025) in some listings).
• Number of pages: 7–8 pages (most catalog records list 8 pages for the E811-09 practice).

Scope

The practice covers instrumental determination of retroreflected chromaticity coordinates of retroreflectors using either telecolorimeters or telespectroradiometers under nighttime (retroreflective) illumination geometry. It addresses general measurement procedures for photometric-range measurements, specifies the use of a CIE Standard Source A to approximate vehicle headlamp spectral distribution, and references Practices E808 (geometry description) and E308 (calculation of chromaticity) for detailed geometry and computation methods. The practice is intended primarily for field and laboratory assessment of traffic sign materials and other vertical retroreflective surfaces to determine color appearance under night driving conditions.

Key topics and requirements

• Definition of nighttime (retroreflective) measurement geometry and required instrumentation (telecolorimeter, telespectroradiometer).
• Use of CIE Standard Source A to represent tungsten-headlamp illumination for chromaticity measurements.
• Procedures for measuring retroreflected spectral radiance and converting to chromaticity coordinates (reference to Practice E308 for calculations).
• Specification of observation/entrance angles (commonly 0.2° observation angle in this practice) and note on alternate angles (e.g., Test Method E2540 for 0.5°).
• Instructions for field and laboratory measurement practices, repeatability considerations, and comparison to minimum requirements for sign replacement decisions.

Typical use and users

Traffic engineering agencies, sign manufacturers, materials labs, retroreflective film and sheeting manufacturers, product acceptance and quality-control personnel, and researchers in road safety and optical materials use this practice to quantify and control the nighttime color appearance of signs and retroreflective devices. It is applied both for field spot-checks of installed signs and for laboratory characterization of candidate materials prior to installation.

Related standards

Commonly referenced and related documents include Practice E808 (geometry for retroreflective measurements), Practice/Test Method E308 (calculation of chromaticity), Test Method E2540 (measurements at 0.5° observation angle), ASTM D4956 (specification for retroreflective sheeting), and various ASTM D and E series standards referenced in retroreflective material testing and traffic device specifications. Revisions and cross-references in catalog listings also show this practice cited by several D-series and E-series standards related to sign testing and appearance measurement.

Keywords

retroreflector, retroreflection, chromaticity, colorimetry, telecolorimeter, telespectroradiometer, nighttime geometry, road signs, traffic sign color, CIE Standard Source A.

FAQ

Q: What is this standard?

A: ASTM E811-09 is a standard practice that specifies methods for measuring the colorimetric (chromaticity) characteristics of retroreflective materials under nighttime, retroreflective illumination and observation geometries.

Q: What does it cover?

A: It covers instrumental techniques (telecolorimeter or telespectroradiometer) for determining retroreflected chromaticity coordinates, selection of reference illuminant (CIE Standard Source A), measurement geometry considerations, and references to calculation and geometry practices (E308, E808). It is intended for both field and laboratory measurements of vertical retroreflective surfaces like traffic signs.

Q: Who typically uses it?

A: Traffic agencies, sign manufacturers and suppliers, testing laboratories, specification writers, and researchers involved in retroreflective materials and sign performance assessment use this practice to ensure consistent nighttime color measurement and specification compliance.

Q: Is it current or superseded?

A: The original was published in 2009 (E811-09). Catalog and reapproval entries show reissues/reaffirmations in later years and an entry listed as E811-09(2025) in recent catalogs; a work item for revision (WK94674) was also recorded in 2025, indicating active maintenance and possible revision activity. Users should confirm the specific edition/reapproval date required by their procuring or regulatory authority when specifying the standard.

Q: Is it part of a series?

A: Yes — E811 is part of ASTM Committee E12 work on image and appearance and is used alongside related practices and test methods (for example E808, E308, E2540) that together define geometry, measurement and calculation approaches for retroreflective and colorimetric testing.

Q: What are the key keywords?

A: Retroreflector, chromaticity, retroreflection, colorimetry, nighttime measurement, telecolorimeter, telespectroradiometer, CIE Standard Source A, traffic signs.