Jung, K . and Fischer, A ., 1993
. An ISO-test method for determining slip resistance of footwear .
Determination of its precision . Safety Science, 16 : 115-127 .
Co-operative tests were conducted by a working group of the "Foot Protection" ISO standardizing committee ISO/TC94/SC3, with the participation of seven countries, using a total of eight test facilities for determining shoe anti-slip characteristics . The underlying examination plan is based on an ISO-draft proposal "The Measurement of the Slip Resistance of Safety, Protective and Occupational Footwear for Professional Use" defining requirements for the testing machines .
The friction coefficients (cof) thereby determined, underlay the statistical evaluation .
The correlation analysis of the raw data showed that correlation could be established between the measured results from most of the test machines, despite different observed values for differentt lubricants . While glycerine gives too low friction coefficients, Berol leads to increased ones .
Different friction coefficients measured for the right and the left shoe of the same pair are of purely coincidental nature .
No correlation was found between the friction coefficients determined for glycerine and 13erol . Friction coefficients measured with one of the two lubricants are not transferable to the other lubricant .
As to precision of the coefficient of friction data, the absolute repeatibility limit as well as the absolute reproducibility limit for Berol are greater than they are in the case of glycerine ; in addition, they depend on the friction coefficient . The test machines reveal a relative repeatibility limit of 10% and a relative reproducibility limit of 70% and 100% respectively, i .e . that there is a 95% reliability of reproducing the same results with the same testing machine within a 10% friction coefficient range whereas the 95% range of the test results obtained with different testing machines comes up to 70','c and 100% of the friction coefficient respectively . Although every single machine furnishes results of acceptable accuracy, the measuring results of the various machines differ considerably .
In contrast to the first inter-laboratory trial by Jung and Schenk . it was possible to improve the repeat ibility limit, while the reproducibility limit became worse .