Standard Test Method for Measurement of Retroreflective Signs Using a Portable Retroreflectometer at a 0.2 Degree Observation Angle
This standard is issued under the fixed designation E1709; the number immediately following the designation indicates the year of onginal 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 indlicates an editorial change since the last revision or reapproval.
1.1 This test method covers measurement of the retroreflective properties of sign materials such as traffic signs and symbols (vertical surfaces) using a portable retroreflectometer that can be used in the field. The portable retroreflectometer is a hand-held instrument with a defined standard geometry that can be placed in contact with sign material to measure the retroreflection in a standard geometry. The measurements can be compared to minimum requirements to determine the need for replacement. Entrance and observation angles specified in this test method are those used currently in the United States and may differ from the angles used elsewhere in the world.
FIG. 1 Annular and Point Aperture Instrument Angles
1.2 This test method is intended to be used for the field measurement of traffic signs but may be used to measure the performance of materials before placing the sign in the field or before placing the sign material on the sign face.
1.3 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 to determine the applicability of regulatory limitations prior to use.
NOTE 1—For each instrument type, the illumination beam is 4° downward For the point instrument, receiver is above source.
FIG. 2 Upright Optical Schematics
2. Referenced Documents
2.1 ASTM Standards:
E 284 Terminology of Appearance
E 808 Practice for Describing Retroreflection
E 809 Practice for Measuring Photometric Characteristics of Retroreflectors
E 810 Test Method for Coefficient of Retroreflection or Retroreflective Sheeting
4.Summary of Test Method
4.1 This test method involves the use of commercial portable retroreflectometers for determining the retroreflectivity of highway signing materials.
4.2 The entrance angle shall be -4°.
4.3 The observation angle shall be 0.2°.
4.4 The portable retroreflectometer uses a instrument standard for standardization.
4.5 After standardization, the retroreflectometer is placed in contact with the sign to be tested,ensuring that only the desired portion of the sign is within the measurement area of the instrument.
4.6 The reading displayed by the retroreflectometer is re- corded. The retroreflectometer is then moved to another position on the sign, and this value is recorded.A minimum of four readings shall be taken and averaged for each retroreflective color on the sign to be tested.