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Comments on ASTM F2508-13

Oren Masory

In 2013 the American Society of Testing and Materials (ASTM) F13 committee on Pedestrian/Walkway Safety and Footwear, adapted a new standard F2508-13 “Standard Practice for Validation, Calibration, and Certification of Walkway Tribometers Using Reference Surfaces”. The purpose of the standard is to provide a procedure for validation and calibration of tribmeters so that that their readings of the Coefficient Of Friction (COF) in wet conditions will be more reliable and consistent. The drive behind for this standard is a well-known problem where there is a large deviation between the readings obtained by different tribometers when measuring the COF between the same surfaces under wet conditions. The standard is based on a study in which four different reference surfaces were ranked according to their slipperiness measured by the number of slips detected while subjects were walking across them. A validated tribometer, according to this standard, is required to correctly rank the slipperiness of reference tiles with statistically significant differentiation between the COF readings. It is should be emphasize that the standard does not dictate any particular COFs’ values for these reference surfaces. The purpose of this paper is to point out some of the difficulties in applying this standard: 1) Different validated tribometers produce different values for the COF of the same ranked surface. Or, vice versa, for the same value of the COF different tribometers will rank the surface’s slipperiness differently; 2) Reference surfaces are not the same; and 3) The COF of the higher friction surfaces depends on the direction of the test which is not necessarily in the direction that a person slipped during the accident. These issues will present confusion in case of litigation and the test results are subjected to subjective interpretations.