Effects of winter Tyre type on roughness and polishing of road surfaces covered with ice and compact snow

Purpose: This field study was designed to compare to what degree various proportions of studded and unstudded winter tyres affect the roughness and polishing of road surfaces covered with ice and compact snow.Methods: Test cars equipped with studded and unstudded winter tyres drove around a test track according to the designed procedure. The main straight section of the track had five lanes, each with a different proportion of cars with studded tyres: 100%, 75%, 50%, 25% and 0% of the respective lane traffic. The remainder were cars with unstudded winter tyres. Each lane included sections of ice and compact snow with subsections for constant speed, braking and acceleration. The lanes were driven 642 times. The ambient temperature was approximately 0 °C during the test.Results: The overall results showed that there was no substantial difference in friction of the road surface between lanes having 100%, 75% or 50% of cars with studded tyres. However, the friction was much poorer in lanes having fewer cars with studded tyres.Conclusions: These results suggest that traffic with 50% of cars having studded tyres results in adequate friction of icy road surfaces in the test conditions