Our former researches revealed that the wind speed and the temperature give a great influence on the snow depth on a roof. The purpose of this experimental study is to obtain indices for evaluating the snow depth on a flat roof, which is the simplest in shape, in relation with meteoro-logical conditions. We have established them from our year's observations of the snow depth on a flat roof and various experimental studies. We can estimate the strength of the drifting snow by using our indices deduced from the average of the wind speed and that of the temperature. Our method proved to be of high reliability agreeing with actual. results obtained in other researches.

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In this paper, first, experimental results of dynamic friction resistance between snow and various sheet materials are shown. These materials are used for structures in snowfall regions. Secondly, the basis of the theoretical analysis is constructed on the investigations for these results. The dynamic friction is not constant but influenced by various factors due to the specific properties of snow. This paper focuses on the effect of snow sliding velocity. The experimental results reveal that the snow temperature, especially near 0°C, the sliding velocity and the surface roughness of sheet materials have effect on the dynamic friction. The equations of the dynamic interaction between snow and sheet materials have been derived from the above mentioned results, and Stribeck curve based on the sliding velocity. By these theories, the relation between friction resistance of snow and sliding velocity can be understood. The results of this paper should be useful for the choice of materials for structures in snowfall regions.

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The studded tire prohibition law has been effective in Japan since 91/92 winter for the purpose of preventing dust pollution generated by studded tire. According to the law, studded tires are prohibited except for emergency vehicles such as fire engines in the areas designated by the Minister of Environment Agency. After April 1992, infringements of the law are punishable with a fine up to 100, 000 yen.
Therefore, in Hokkaido especially Sapporo area it can be considered "The first year of studless" in 92/93 winter.
This paper reports the circumstances behind enactment of the law, the effects of the enforcement of the law to road environment, road surface condition and road pavement and marking, equipping percentage of studded tires, traffic accidents, traffic characteristics and performance of "studless tire", etc and problems that follow.

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