ASTM E3320-21 PDF

SIGNIFICANCE AND USE 5.1 The quality of the pavement marking is determined by the coefficient of retroreflected luminance, RL, and depends on the materials used, age, wear pattern, application method, pavements surface, and other conditions. 5.2 Under the same conditions of illumination and viewing, larger values of RL correspond to higher levels of visual performance in dark conditions. 5.3 Retroreflectivity of pavement (road) markings degrades with traffic wear and requires periodic measurement to ensure that sufficient line visibility is provided to drivers. 5.4 MRUs are used to measure RL values of road markings while moving at traffic speed, and can be used for longer stretches of road than portable instruments and in cases where the use of portable instruments require extensive precautions, in particular on motorways. 5.5 The measurement geometry of the MRU is based on a viewing distance of 30 m, a headlight mounting height of 0.65 m directly over the stripe, and an eye height of 1.2 m directly over the marking according to CEN 1436 and Test Method E1710. 5.6 MRUs are to be calibrated, maintained, and operated according to instructions by the instrument supplier or manufacturer. 5.7 It shall be the responsibility of the user to employ an MRU fulfilling the required specifications in this standard. SCOPE 1.1 This test method covers measurement of the retroreflective properties of horizontal pavement marking materials containing retroreflecting optics, such as traffic stripes and surface symbols, using a mobile retroreflectometer unit that can be operated at traffic speed, mounted on a vehicle to measure the retroreflection at a prescribed geometry. 1.2 The entrance and observation angles of the MRU affect the readings. As specified by the European Committee for Standardization (CEN) and in Test Method E1710, the entrance and observation angles shall be 88.76° and 1.05°, respectively. 1.3 This test method is intended to be used for field measurement of pavement markings at traffic speed. 1.4 This test method is intended to be used for retroreflectivity measurement of dry pavement markings. 1.5 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard. 1.6 This standard does not purport to address regulatory and safety regulations of the MRU and its use. It is the responsibility of the manufacturer to fulfill regulatory standards. 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. 1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.