Traction and Braking Performance Comparison between Manufactured and Natural Snow Track Surfaces in a Controlled Environment

ABSTRACT Prepared hard-packed tracks made from manufactured and natural snow were compared under controlled indoor conditions at approximately −8 °C and 85% relative humidity. Three tire sets were evaluated using repeated acceleration and braking tests executed by experienced test drivers. Despite similar mean compacted track index (CTI) hardness values of 83.8 and 84.9, the tracks produced clear differences in frictional performance. Mean acceleration time was 4.43 s on manufactured snow and 4.92 s on natural snow, whereas mean braking distances were 12.35 and 13.93 m, respectively, equating to 11% longer acceleration time and 13% longer braking distance on natural snow. Manufactured snow also exhibited lower within-test variability: average standard deviations on the two surfaces were 0.08 vs 0.11 s for acceleration and 0.17 vs 0.36 m for braking. Degradation measurements indicated less negative performance change on manufactured snow, although this difference was less distinct. The snow surfaces generally displayed ∼0–1% in performance change. The two tested Nordic friction tires performed similarly and outperformed the tested European friction tires on both tracks, indicating that the Nordic friction tires were more suitable for pure snow tracks. The results show that similar CTI hardness does not necessarily imply similar tire–snow performance. Manufactured snow provided the more stable and reproducible test surface under the investigated conditions. Possible contributions from snow mechanical response, multiscale roughness, and rubber–surface contact are discussed qualitatively using snow mechanics and the Persson friction framework, but the governing mechanisms were not measured directly.