Original publication: 2020 | Peer-reviewed journal article
Source authors: S. R. Lewis, K. Hallas, B. Keen, G. Hunwin, R. Shaw and M. J. Carré
About this research
Understanding how well footwear grips a surface requires a test method that reflects the mechanical conditions of a pedestrian slip. Standardised mechanical methods provide repeatable friction measurements, but the interaction between a complete shoe, the floor and any contaminant is complex.
This research developed and evaluated a new Shoe Slip Tester (SST) intended to provide a practical way to test complete footwear while reproducing important features of heel contact during walking.
It was undertaken collaboratively by researchers from the University of Sheffield, the Health and Safety Laboratory (HSL) and SyxRail.
A different approach to measuring footwear grip
The research rig used pneumatic actuation to bring a shoe into contact with a flooring sample. The apparatus incorporated an articulated ankle arrangement and adjustable shoe and heel orientation to investigate the transition between grip and slip.
The objective was to combine mechanically controlled testing with contact conditions relevant to human footwear performance, offering a repeatable approach to distinguishing shoes that behave differently on the same surface.
How the research was conducted
Four footwear models were tested under water contamination on a stainless-steel flooring surface. The SST experiments varied pneumatic test pressure (3, 4 and 5 bar) and heel contact angle (7°, 14° and 21°) and compared results with those from the HSL human-based ramp test.
The investigators assessed how changing the test settings influenced the measured friction and how closely results corresponded with the ramp method.
Key findings
The SST differentiated between footwear designs.
The tested models displayed a substantial range of grip performance. The apparatus identified meaningful differences between the shoes rather than producing essentially identical results from every test.
Selected operating conditions produced close agreement with the human ramp.
With the test set to 5 bar and 21° heel angle, the mean signed percentage difference across the four footwear models was approximately 3% relative to the ramp results. This demonstrated that, with suitable settings, the new apparatus could reproduce the relative performance observed using an established human-based reference.
Test conditions materially affected the results.
Changes in impact pressure and heel angle produced clear differences in measured performance, reinforcing the need to establish appropriate operating conditions for a mechanised whole-shoe test.
The significance of the research
The study demonstrated the feasibility of a practical, mechanically controlled footwear slip tester that incorporates critical aspects of heel contact rather than relying solely on a flat sliding-contact measurement.
Its value lies in the development and evaluation of the apparatus and in the evidence that footwear performance can be differentiated in a way consistent with the human-based ramp under the studied conditions.
As a development study, the experiments were limited to four footwear designs and the particular flooring and contamination conditions investigated. They did not establish universal equivalence to every other slip-resistance method or real-world slip outcome.
Why it remains relevant
The research established a foundation for more practical testing of complete footwear with controlled physical contact. It also illustrates the scientific discipline required when developing a measurement method: determining which operating conditions matter and comparing the results with a relevant reference.
Original research
Lewis, S. R., Hallas, K., Keen, B., Hunwin, G., Shaw, R. and Carré, M. J. (2020). Development of a New Shoe/Floor Slip Resistance Test Rig. Tribology International, 151, 106500. DOI: 10.1016/j.triboint.2020.106500.