Significance and Use
Measurements of RI made by this test method, with the 0.2° observation angle, are related to visual observation of raised retroreflective pavement markers at distances of approximately 220 m (720 ft) for cars or approximately 440 m (1440 ft) for trucks when illuminated by tungsten filament light sources such as car headlights.
There are some castings that block vehicle illumination of a portion of the marker mounted within it. In this case, measured RI can be significantly lower than when the marker is photometered outside the casting, but will correspond to the visual observation.
The test method is not applicable to raised pavement markers mounted in depressions cut into the pavement.
The coefficient of luminous intensity of raised retroreflective pavement markers degrades with traffic wear and requires periodic measurement to ensure that sufficient visibility is provided to the driver.
The quality of the pavement markers as to materials used, age and wear pattern, will have an effect on the coefficient of (retroreflected) luminous intensity. These conditions need to be observed and noted by the user.
1.1 This test method covers the measurement of the retroreflective properties of raised retroreflective pavement markers at a prescribed geometry, by means of a portable retroreflectometer that can be used in the field. The measurements can be compared to minimum requirements to determine the need for replacement.
1.2 The observation angle specified for retroreflectometers in this test method is that currently specified for raised pavement markers in the United States and may differ from the angles used elsewhere. For other jurisdictions, replace the observations angle specified herein with the observation angle specified by the pertinent agency.
1.3 This test method is intended to be used for field measurement of raised retroreflective pavement markers but may also be used to measure the performance of new markers before they are placed in the field.
1.4 This test method covers measurements of raised pavement markers mounted on a road surface or mounted in snow-plowable metal castings.
1.5 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.6 The 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.