Differences in slip resistance measurements under dry and wet conditions on the same smooth walkway surface may occur when testing with a Neolite®4-Test-Liner (NTL) test foot using the PIAST [Slip Test Mark II] and VIT [English XL] tribometers. To investigate the causes of these differences, two sets of NTL test feet (smooth and grooved) for each instrument were cut from the same piece of material. Slip-resistance measurements were made under both wet and dry conditions. The same operator was used for each tribometer, an observer monitored each test, and all testing was performed in the same room at the same time. The walkway surfaces were commercial floor materials.
On dry surfaces, the measured slip resistance using the grooved test foot was the same or lower than the results using the smooth test feet. On wet surfaces, measured slip resistance using the grooved test feet increased slightly with the VIT and significantly using the PIAST. Averaged test results showed that the use of the grooved test feet on both instruments brought the readings these devices closer to each other; using the grooved test foot, the readings generated by the PIAST and VIT were not significantly different.