Despite the long history on the study of friction and ease of sliding, there are few studies on friction of metal with smooth surfaces such as ice. The aim of this study was to determine the best surface roughness measure that correlates with the ease of sliding. Ice was chosen as the smooth surface since it is easy to produce. Stainless steel blocks were abraded with different grades of sandpaper to produce parallel scratches in the metal surface. Single roughness measures (Ra, Sa, SSk, Sds, Sdq, and RSm) and RSm/Sa that is related to the Criterion for Contact were extracted from a 3D profilometry measurement on metal blocks scratched with 400 to 3000 grades of sandpaper. The scratched metal blocks were slid down an ice-track to determine the sliding speed of blocks with different roughness. The relationship between the roughness parameters and sliding velocity was then investigated. It was shown that the best correlation between the surface roughness and the sliding speed was for the "Criterion for Contact" roughness measure, RSm/Sa. A critical value of roughness was essential for achieving the best sliding. A method was established for measuring and characterizing the roughness of a surface for applications requiring low friction.