A Critical Analysis of the Relationship Between Shoe-Heel Wear and Pedestrian/Walkway Slip Resistance

This study seeks to clarify issues in pedestrian/walkway slip safety by exploring in detail the relationship between shoe-heel wear and slip resistance. Importantly, this paper addresses the fact that slip resistance changes as a result of wear-generated changes in the shoe-bottom and, to a lesser extent, the test surface. Insights from this paper may provide a better way of characterizing slip resistance than the commonly used averaged coefficient-of-friction (COF) value that would be compared against single-value pedestrian-friction safety thresholds. Specifically, we have derived an alternative, systematic slip resistance measurement methodology by observing the variation of COF with changes in the friction force as a function of interface wear between a shoe heel and floor surface under dry test conditions. Surface changes of both bodies were quantified using two extreme roughness parameters: Rpm and Rvm. It was found that massive wear occurred on the shoe-heel surface from very early stages of sliding and continued until the surface layer was heavily worn out. Heel contact conditions, such as initial strike time and position, changed significantly with wear evolution and, importantly, were directly related to the displacement of the friction force. Our results clearly showed that COF is not constant with respect to shoe-heel wear and, thus, friction is a function of a given set of materials as well as environmental and wear conditions.