Studies on traffic disaster in cold regions caused by road freezing and drifting snow

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Observations of road surface freezing were carried out at Sekihoku Pass on Road 39 and Tanno Tunnel on Road 333 in Hokkaido during two winter seasons (1993-94 and 1994-95). In Sekihoku Pass, the surface temperature was automatically observed on a road on a usual road, a road on a bridge (bridge road) and a road in snowshed (snowshed road). The bridge road surface was more frequently frozen than usual road, especially in the beginning of winter season, October and November. In the winter season, January and February, the surface temperature of bridge road was lower than that of usual road about 1 or 2 ﾟC,but higher in spring season, after May, which means a bridge road is more quickly heated and cooled than a usual road. On the snowshed road, sherbet surface often appeared until April while other surface was frequently dry, which means the solar radiation does not contribute to heating the surface in a snowshed.The surface temperature was simulated from air temperature, wind speed and radiative temperature of sky as an index of long-wave radiation. The obtained temperature trends were well agreed with the observed data on the three types of road whereas the average was lower about 1-2ﾟC.The outdoor experiments for road heating was carried out at Kitami. The most economical heating operation was obtained using of a precipitation sensor and a freezing sensor.Calculating the movement of individual snow particles, the drifting snow around obstacles was simulated to evaluate the snow fence performance. For the air flow conditions, the average stream line was given from observation and the turbulence components were assumed as sinusoidal variation. In this model the movement of each snow particle was calculated, and accumulating lots of particle movement the formation of snow drift was reappeared.