Variable Inclinable Stepmeter: Using Test Subjects to Evaluate Walkway Surface/Footwear Combinations

A variety of techniques have been used to measure walkway-surface/shoe-outsole slip resistance, employing both stationary and portable devices. In operation, typically, a shoe outsole material is placed in contact with a walkway surface and the ratio of the tangential force to the normal force at motion inception is a measure of the static coefficient of friction between the surfaces.

Recently introduced in Europe is a motorized inclinable ramp. A test subject walks both up and down the inclineable ramp and the ramp angle is incrementally increased until a slip occurs. The tangent of the ramp angle when slip occurs is an indication of the slip resistance between the walkway and shoe bottom. The ramp surface can be covered with a liquid for testing wet floor surfaces

The device described in this paper, called a ‘Stepmeter,’ is a simplified ramp device. It has a test subject stepping down with one foot on a variably inclinable ramp surface. The test subject's other foot rests on a flat, level surface. The ramp angle is incrementally increased until the subject's foot slips. The tangent of the angle at slip is a measure of the slip resistance between the shoe bottom and walkway surface. Tribometer test feet were constructed from the same shoe outsoles as on the shoes worn by the test subjects. These test feet were used in two portable tribometers on the same test surfaces as used in the device we developed.

Preliminary results indicate that this device can reproduce consistent results. Stepmeter results and the (limited) portable-tribometer slip resistance test results were similar.