The quality of the pavement marking is determined by the coefficient of retroreflected luminance, R_L, be it dry or wet, and depends on the materials used, age, and wear pattern. These conditions shall be observed and noted by the user.

Under identical conditions of headlight illumination and driver’viewing, larger values of R_L correspond to higher levels of visual performance at corresponding geometry.

The pavement marking’measured performance in conditions of continuous wetting may be used to characterize the performance of the marking on the road as water is continuously falling on it and may be representative to a period of rain. This performance of the marking may be different than that experienced when the markings are just wet or damp.

Retroreflectivity of pavement (road) markings degrades with traffic wear and requires periodic measurement to ensure that sufficient line visibility is provided to drivers. For example see Specification D 6359 for dry reflectivity requirements.

For a given viewing distance, measurements of R_L made with a retroreflectometer having a geometry corresponding to that viewing distance are a good indicator of the visual ranking of the material measured.

As specified by Test Method E 1710, the measurement geometry of the instrument is based on a viewing distance of 30 m, an eye height of 1.2 m and a headlight mounting height of 0.65 m (see Appendix X1).

Newly installed pavement markings may have a natural surface tension or release agents which prevent the wetting out of the product by rain/water. This phenomenon produces an interference when assessing the wet characteristics of a pavement marking. Attempt to measure markings with this surface “non-wetting” of the water may give higher values. This condition is short lived and markings that have been on the road for one month or more do not exhibit this non-wetting.

It shall be the responsibility of the user to employ an instrument having the specified observation and entrance angles.

1.1 This test method covers the measurement of the wet retroreflective (R_L) properties of horizontal pavement marking materials, such as traffic stripes and road surface symbols, using a portable or mobile retroreflectometer that can be placed on or before the road marking to measure the retroreflection at the prescribed geometry.

1.2 This method of measuring of the wet retroreflective properties (R_L) of pavement markings utilizes a method of continuously wetting the marking during measurement with the retroreflectometer (see Fig 1).

Note 1—Test Method E 2177 may be used to describe the performance of pavement markings in conditions of wetness after a period of rain.

1.3 This test method specifies the use of portable or mobile reflectometers that can measure pavement markings per Test Method E 1710. The entrance and observation angles required of the retroreflectometer in this test method are commonly referred to as "30 meter geometry."

1.4 This test method is intended to be used for field measurement of pavement markings but may be used to measure the performance of materials on sample panels before placing the marking material in the field.

1.5 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 determine the applicability of regulatory limitations prior to use.