Affiliations: Finnish Institute of Occupational Health, Department
of Occupational Safety, Topeliuksenkatu, Helsinki, Finland | Liberty Mutual Research Center for Safety and Health,
Hopkinton MA, USA | Finnish Institute of Occupational Health, Department
of Physics, Topeliuksenkatu, Helsinki, Finland
Note: [] Corresponding author: Raoul Grönqvist, Finnish institute of
Occupational Health Department of Occupational Safety, Topeliuksenkatu 41 a A,
Fin-00250, Helsinki, Finland
Abstract: The variation in utilized and available friction over shoe-floor
contact time was determined in the presence of high- and low-viscosity
contaminants. The objectives were to improve the validity of slipperiness
evaluations and to find better criteria for safe friction during heel strike.
The utilized friction coefficients for six shoe types were determined during
gait-trials with male participants. The available friction coefficients of
these shoes were measured with a test rig simulating heel slipping. The
experiments were performed on a stainless steel floor with concentrated
glycerol ('oily' condition) and diluted glycerol (1:10 in water) as
contaminants. It was hypothesized that any single friction measurement
criterion would be an insufficient predictor for safe gait with no slip or with
slip recovery, not leading to a fall. The results showed that both transitional
friction (time-intervals from zero to about 250 ms of heel contact) and steady
state kinetic friction (time-intervals from about 250 ms to 450 ms) properties
in the shoe and floor interface play an important role in slipperiness
measurement and slip/fall risk assessment. The role of static friction in the
risk assessment remained unclear.
Keywords: slipperiness measurement, available friction, utilized and required friction, heel contact phase, slip/fall risk, walking safety
