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Repeatability and Bias of Two Walkway Safety Tribometers

Journal of Testing and Evaluation

Christopher M. Powers, Ph.D., P.T.

Assistant Professor, Department Biokinesiology and Physical Therapy, University of Southern California, 1540 E. Alcazar St. CHP-155, Los Angeles, CA 90033

Komelia Kulig, Ph.D., P.T.

Associate Professor of Clinical Physical Therapy, Department Biokinesiology and Physical Therapy, University of Southern California, 1540 E. Alcazar St. CHP-1 55, Los Angeles, CA 90033

James Flynn, P.E.

J₂ Engineering Inc., 7636 N. Ingram Avenue, Suite 108, Fresno, CA 93711

And

John R. Brault, M.S.

Senior Biomechanist, Biomechanics Research & Consulting Inc., 840 Apollo St., Suite 218, El Segundo, CA 90245

Abstract: Falls resulting from slips on walkway surfaces are a significant source of injury in society. To measure friction between the floor and the shoe, various types of tribometers and ASTM standards have been developed to assess walkway slip-resistance with the goal of improving pedestrian safety. The purpose of this study was to determine the repeatability and bias of the PIAST and VIT tribometers under both dry and wet conditions. Both devices were tested on an AMTI force platform over a wide range of angles. Bias was assessed by comparing the tribometer slip resistance reading to the actual Fx/Fz ratio measured by the force plate, while reliability was established by evaluating the ability of the tribometers to reproduce Fx, Fz and the Fx/Fz ratio. Both tribometers demonstrated high degrees of validity and reliability under both wet and dry conditions, however each measured different slip-resistance values for the same surface. Further study should be directed at establishing which tribometer best simulates initial foot contact during gait with respect to measuring slip-resistance.