<p>Improvement study of the prediction methodology which represents the friction properties of rubber blocks on ice has been conducted. The 2-D coupled block model with sipes and the mechanical analysis methodology have been applied towards the intuitive understanding of tribology mechanisms and improvement of grip performances of winter tires on icy road surface. The effects of the ploughing of ice surface by sipe edges and the decrease of actual contact area caused by the block deflection are taken into account in order to evaluate the effects of the sipe density and the block stiffness of tread pattern. It had been derived that the contribution of ploughing resistance of sipe edges to friction coefficient on ice could be negligible and that the main factors of friction improvements by sipe edges were assumed to be "scraping effects" which improved adhesive friction and adhesion ratio in the contact patch by scraping away softened ice layer and water film on the ice surface. The characteristics of predicted friction coefficients regarding the sipe density had been partly validated with experimental results. Predicted friction coefficients were described as the diagram of the sipe density and the block stiffness. The diagram expressed that the compatibility of these two prime factors would be effective in the increase of friction coefficient on ice. This result suggests the potential of sipe structure improvements on the tread pattern of winter tires.</p>