1.1 This test method covers a measurement of the wet retroreflective (R_L-Rain) properties of horizontal pavement marking materials, such as traffic stripes and road surface symbols.

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

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

1.3 This test method is most suitable for laboratory use under controlled conditions, but may also be used for field measurements when the necessary controls and precautions are followed.

1.4 This test method specifies the use of 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."

1.5 This test method has been shown to produce reasonable results for pavement marking systems with optics having an index of refraction greater than 2.0 and structured markings having vertical structures greater than or equal to 3 mm. Users should exercise caution when using this test method for pavement marking systems with optics having an index of refraction less than 2.0 or markings having vertical structures less than 3 mm.

1.6 Results obtained using this test method should not be the sole basis for specifying and assessing the wet retroreflective effectiveness of pavement marking systems. Users should complement the results of this test method with other evaluation results, such as nighttime visual inspections.

1.7 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.

Note 2 - An alternative test method designed to better represent the retroreflective efficiency of pavement marking systems under typical rain events is under development.

FIG. 1 Illustration of Measurement