Currently, no standardized method exists for testing shoes on ice. SATRA's slip test machine includes a test method for different ice surfaces and the Kite Research Institute has developed a shoe grip test on ice suggesting potential changes in standards. With these tests in mind, we aimed to place a walking ramp test outside in a winter environment and investigate its potential for testing winter shoes and explore the applicability of the ramp test for classifying the friction of winter shoes.

11 pairs of commercial winter shoes have been examined when walking on a slope with a walking length of 3.5 m at different angles, and the maximum slope where slipping occurs has been detected. A single participant has walked up and down twice, and we registered a slip when it happened repeatedly. We tested the shoes at specific ramp angles between 0 and 30 degrees. The ice was prepared by brushing icy water perpendicular to the walking direction a night before the tests. The soles of winter shoes were prepared according to the cleaning protocol of ISO 13287 (European Committee for Standardization, 2019). Three measurement series were completed, one at – 8.5℃ and two at around – 1.4℃. 

The outdoor ramp test produced consistent results under the same temperature condition, revealing measurable differences, including variations between uphill and downhill measurements. However, comparing friction at different temperatures is challenging because of its critical effect, especially in the presence of ice. It is recommended that the ice is produced in a well-documented process that considers real conditions, such as testing the ice layer on asphalt, and its temperature and topography should be well documented during the tests. Labelling systems categorize shoes based on critical angles. However, looking at performance only at discrete angles can limit the differences observed between shoes.