Falls due to slipping are one of the costliest injuries in the workplace. The coefficient of friction (COF) between the worker’s footwear and the floor is the main physical factor that determines slipping. There are two main categories of slip risk assessment (SRA) devices: laboratory-based devices that re-create the mechanics of walking, but which are not portable, and field tribometers that do not re-create human heel-strike kinematics. This paper investigates the reasons why no SRA device is simultaneously portable, biofidelic, and validated against human slip outcomes, and proposes design requirements for such a device. Literature was located through four databases (Scopus, Web of Science, PubMed, and IEEE Xplore). Through examining existing SRA devices according to three independent criteria: portability, biofidelity, and validation against human slips, it becomes evident that no current device fulfills all three criteria. The reasons for the lack of devices that fulfill these criteria are that wearable sensors rarely measure shear and normal force simultaneously between shoe-floor interactions, that environmental conditions are rarely incorporated into the measurements of those forces, and that portable SRA devices are almost never validated against gait-laboratory reference data. Each of these factors presents quantified design requirements for the next generation of SRA devices, including a sampling-rate specification based on the measured frequency content of gait rather than from convention, and a validation protocol grounded in established statistics. This paper, therefore, presents a concrete design specification for such a device. This specification provides the criteria against which the next generation of SRA devices can be built and evaluated.

Keywords

Coefficient of friction; slip risk; tribometer; wearable sensing; gap analysis; design requirements