Evaluation of Dense-Graded Asphalt Surfaces Texture Indexes Isotropy and 2D–3D Equivalency

Abstract

Pavement macrotexture is vital for skid resistance, especially in wet or icy conditions. Laser-based profilers are widely used to collect pavement macrotexture data due to their accuracy and reliability. While three-dimensional (3D) approaches provide area-based macrotexture characterization, most of these approaches require stationary measurements and traffic control, which limits their use for network-level evaluations. As a result, two-dimensional (2D) indexes are commonly used to describe pavement texture features. However, with advancements in laser texture scanners, 3D testing methods are expected to become standard in the future. This paper evaluated 15 2D surface texture indexes computed using different approaches seen across the pavement engineering literature. The study used data from 214 field cores taken from various pavements in North Carolina, scanned using a rapid laser texture scanner (rLTS), a static texture measuring device capable of 3D scans. The findings revealed that the only index that is truly isotropic (there is no statistically significant difference in the horizontal and orthogonal direction) is the mean absolute height (Ra). The root mean squared (RMS) and variance in height (Rva) showed isotropy only when the data was detrended and denoised. However, all other indexes demonstrate anisotropy, indicating that the measurement direction significantly impacts their values. This research sets the stage for future comparisons between 2D and 3D indexes, which could enable the utilization of historical texture data in pavement performance modeling and decision-making once 3D testing becomes more widespread.