5.1 This practice is suitable for the calculation of the average macrotexture depth from profile data. The results of this calculation (MPD) have proven to be useful in the prediction of the speed dependence of wet pavement friction.
5.2 The MPD can be used to estimate the result of a measurement of macrotexture depth using a volumetric technique according to Test Method E965. The values of MPD and MTD differ due to the finite size of the glass spheres used in the volumetric technique and because the MPD is derived from a two-dimensional profile rather than a three-dimensional surface. Therefore, a transformation equation must be used.
Note 2: The two concepts are closely related and have strong correlations; these correlations can differ depending on the pavement types used to establish the correlation. Although they are not the same physical characteristic, the MPD measurement technique is intended to replace the manual MTD measurements.
5.3 This practice may be used with pavement macrotexture profiles taken on actual road surfaces or from cores or laboratory-prepared samples.
5.4 Aggregate size, shape, and distribution are features which are not addressed in this practice. This practice is not meant to provide a complete assessment of texture characteristics. In particular, care should be used when interpreting the result for porous or grooved surfaces.
5.5 This practice does not address the problems associated with obtaining a measured profile. Laser or other optical noncontact methods of measuring profiles are usually preferred. However, contact methods using a stylus also can provide accurate profiles if properly performed.
1.1 This practice covers the calculation of mean profile depth from a profile of pavement macrotexture.
1.2 The mean profile depth has been shown to be useful in predicting the speed constant (gradient) of wet pavement friction.
1.3 A linear transformation of the mean profile depth can provide an estimate of the mean texture depth measured according to Test Method E965.
Note 1: A similar method for measurement and calculation of MPD is presented in ISO 13473-1. The only technical differences are the way spike removal and extreme MSD removal are calculated. Despite these differences, the ASTM and ISO methods will arrive at the same results, with only insignificant differences in normal cases. The ASTM method for spike removal applies calculations which are much more complicated but will result in less correct samples which are adjacent to spikes being removed. The extreme MSD removal in the ASTM method will also be more precise than the ISO method, but at the expense of more complicated calculations. Significant differences will potentially appear only on some uncommon or special textures, such as tined or grooved cement concrete pavements. In the next few years, attempts will be made to coordinate the calculations with a view to make them identical in both standards. The ISO standard includes eight annexes with additional information, for example about uncertainty calculations and how users can check their software against standard texture profiles. A note corresponding to this one will be included in the ISO 13473-1 standard.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.6 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.
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