FOOTWEAR FRICTION ASSESSED BY WALKING EXPERIMENTS

Analyses of accidents and gait biomechanics by Strandberg (1983) point to the substantial influence on human safety of walking friction on contaminated surfaces. However, friction meter data often lack validity according to a past interlaboratory comparison. Therefore, the slip-resistance of 18 types of footwear (tof) on three contaminated floorings was assessed by experiments with 12 well-trained subjects, walking in a triangular closed path as fast as possible without slipping and falling into the safety harness. From the lap time the average value of the friction utilization (tfu) was computed with a model by Lanshammar and Strandberg (1985). Ground reaction force measurements from individual steps with sliding motions confirmed that the tfu was close to the actual coefficient of friction. On the most slippery surface the average time over five laps ranged between about 7 s and 20 s for the 18 tof. The corresponding tfu means were about 0.3 and 0.04. The 18 tof could be separated at about ten significantly different tfu levels. On the other two surfaces, the lap time variation was less pronounced and the rank order was different for certain tof. The lap time varied least between the three surfaces for the most slip-resistant tof - from 7 s to 8 s, while other tof varied between 9 s and 20 s. The results elucidate the influence of flooring and footwear parameters such as pattern, hysteresis, hardness and stiffness. (TRRL)