Abstract
To elucidate the mechanism whereby vehicles become stranded on roads during heavy snowfall, we investigated the conditions of the compacted-snow road surface under a standing vehicle during heavy snowfall and conducted standing vehicle tests, tire spinning tests and vehicle start tests on compacted-snow roads.
We found that compacted-snow road surfaces with the formation of pits and with a rough, wavy, irregular profile were generated under the standing vehicle. From the vehicle tests, we found the following. The wheel load of a standing vehicle, the heat transfer from the vehicle and the spinning of the tires at starting promote the melting and compaction of snow. When snow melts and is compacted under the tire, the tire starts to sink into the snow. At the same time, the sliding friction coefficient of the road surface directly under the tire decreases. It was shown that the stranding of vehicles is less likely to occur as the wheel load increases.
The mechanism of vehicle stranding is as follows. Heavy snowfall reduces the smoothness of trafficability and increases vehicle standing time and the number of starts. The increases in standing time and number of starts induce the formation of pits and decrease the friction coefficient. They promote tire spinning that further deepens the pits and decreases the sliding friction coefficient. This negative cycle leads to the stranding of vehicles. This paper gives a chart that shows the flow leading to the stranding of vehicles and the flow for avoiding it.
