Proof of shoe slip-resistance by a walking traction test

Abstract

Manning, D.P., Jones, C. and Bruce, M., 1990. Proof of shoe slip-resistance by a walking traction test. Journal of Occupational Accidents, 12: 255–270. There is no universally acceptable or reliable method of measuring shoe and floor friction, and few of the many published methods are capable of measuring coefficient of friction (c.o.f.) of shoes worn on the feet. A new walking traction test is described, in which a test subject walks on slippery floor surfaces, pulling against a set of springs and the maximum c.o.f. attained before the feet slip, is measured. Three soling materials were selected from a large number previously tested by a different method of measuring c.o.f. One had registered higher than average c.o.f. and the other two lower than average c.o.f. The three materials were moulded onto bowling shoes with flat soles and no separate heel or tread pattern. One set of three pairs was reserved for water lubricated surfaces and the other set for oily surfaces. Coefficient of friction of the shoes was measured by the new walking test on three separate floor surfaces lubricated in turn with water and oil. The shoe soles were then abraded or polished in ten stages with an orbital sander. Surface roughness and c.o.f. were measured after each abrasion treatment. With successive abrasion treatments, the soling selected for above average c.o.f. gradually became rougher than the other two materials and it nearly always recorded higher c.o.f. readings when tested by the walking traction method. Its superior grip was demonstrated at roughness readings above 15 microns on water lubricated floors; c.o.f. of 0.43 was achieved on all three floors. The other two solings could not be roughened more than 15 microns. On oily surfaces, soling roughness of 21.5 microns only produced a c.o.f. of 0.2. Permanent roughness of solings is one of the properties needed for safer walking in slippery conditions. This new walking traction test convincingly measures shoe and floor friction up to a maximum of 0.43 and will assist the search for slip-resistant footwear.