The need for better metrics for floor-tile topography: Conventional metrics correlate only modestly with shoe-floor friction

Roughness metrics measured with stylus profilometry are commonly used to explain a floor's friction performance, yet these metrics inconsistently predict shoe-floor friction. While strong correlations have been shown for systematically modified flooring, the goal of this study is to address a gap regarding the predictive ability of these metrics across heterogeneous porcelain flooring products. The predictive ability of four roughness metrics on oily friction performance was assessed using 23 floors and 4 shoe designs. Roughness was moderately correlated with friction (r ranged from 0.374 to 0.760). These results are a reference point for future studies that aim to improve predictions using novel surface characterization approaches that include multiple scales.