# Estimation of the Kinetic Coefficient of Friction of Asphalt Pavements Using the Top Topography Surface Roughness Power Spectrum

## TL;DR

This paper introduces a new method to estimate asphalt pavement friction using surface roughness data, improving accuracy by focusing on top surface features.

## Contribution

The novel approach uses top surface roughness power spectra and a cutting plane at 0.5 RMS height to estimate kinetic friction more accurately.

## Key findings

- The cutting plane at 0.5 RMS height showed highest robustness across pavement types.
- Estimated COF values matched measured values closely for all four tested surfaces.
- The method excludes non-contacting deep roughness components, improving friction estimation.

## Abstract

This study proposes a method for estimating the kinetic coefficient of friction (COF) for asphalt pavements by improving and applying Persson’s friction theory. The method utilizes the power spectral density (PSD) of the top surface topography instead of the full PSD to better reflect the actual contact conditions. This approach avoids including deeper roughness components that do not contribute to real rubber–pavement contact due to surface skewness. The key aspect of the method is determining an appropriate cutting plane to isolate the top surface. Four cutting strategies were evaluated. Results show that the cutting plane defined at 0.5 times the root mean square (RMS) height exhibits the highest robustness across all pavement types, with the estimated COF closely matching the measured values for all four tested surfaces. This study presents an improved method for estimating the kinetic coefficient of friction (COF) of asphalt pavements by employing the power spectral density (PSD) of the top surface roughness, rather than the total surface profile. This refinement is based on Persson’s friction theory and aims to exclude the influence of deep surface irregularities that do not make actual contact with the rubber interface. The core of the method lies in defining an appropriate cutting plane to isolate the topographical features that contribute most to frictional interactions. Four cutting strategies were investigated. Among them, the cutting plane positioned at 0.5 times the root mean square (RMS) height demonstrated the best overall applicability. COF estimates derived from this method showed strong consistency with experimentally measured values across all four tested asphalt pavement surfaces, indicating its robustness and practical potential.