Volume 41, Issue 5 (September 1996)
Required Coefficient of Friction Versus Top-Piece/Outsole Hardness and Walking Speed: Significance of Correlations
Slip resistance of shoes in relation to walkway surfaces is of importance to forensic science. Pedestrians adapt to changes in shoe construction, walkway, and interface characteristics by altering patterns of movement. The instantaneous ratio of tangential to normal ground reaction forces (required coefficient of friction) is affected by such movement alterations. Slip probability depends on the ratio of required to available coefficient of friction (μr/μa). However, there are practical problems in application of this concept. Adequate assessments of the safety of footwear/walkway-surface interactions should take into account subject tests of μr in actual walking scenarios as well as material tests of μa and relevant footwear/walkway characteristics.
Based on the literature, this paper discusses the relationship of μr to top-piece/outsole hardness and walking speed. A pilot experiment is described in which subjects walked across a force plate at a series of increasing speeds wearing shoes with the top-piece/outsoles replaced by various test materials. Correlations of μr versus top-piece/outsole hardness and walking speed are presented from data analysis of a single representative subject. The paper explores how biomechanical adaptations of the subject to his foot-wear may account for the fair-moderate correlations observed.