Development of a Mean Profile Depth to Mean Texture Depth Shift Factor for Asphalt Pavements

The initial condition of a newly constructed pavement structure, also known as the zero point, provides valuable information and can be included in pavement management systems. The zero point data for the initial macrotexture level can be gathered both quickly and efficiently by measuring the mean profile depth (MPD) of the pavement surface with a laser profiler immediately after the end of the construction phase and before the road pavement is opened to traffic. However, in many countries the specifications for macrotexture levels during this phase are gathered through the mean texture depth (MTD) index derived from the sand patch method, which is both location specific and time-consuming. Thus, the study presented in this paper investigated the applicability of the ASTM E1845 equation to the field data collected from a newly constructed highway and then developed a methodology to form a shift factor that could allow the direct estimation of MTD data with MPD data. The investigation findings showed that the applicability of the ASTM equation was not validated for the particular highway, a conclusion that was drawn in other relevant investigations. On the contrary, the developed factor to shift MPD data to MTD appears to be effective for use by pavement engineers with validation results supporting the conclusion. This paper presents details highlighting the need to consider the individual characteristics of each pavement surface, as improper use of the ASTM equation could lead to erroneous results.