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利用元胞自动机，建立了冰雪条件下城市道路单车道和双车道交通流微观模型。针对冰雪条件下驾驶员出于安全考虑降低车速、保持较大车间距的现象，细化了元胞尺寸，引入反映不同冰雪条件的速度因子参数和间距因子参数。通过数值模拟，得出了正常天气和冰雪天气下的车辆速度、密度、流量间的关系曲线，并分析了不同冰雪条件对交通流的影响。研究发现，中雪条件下的车速波动程度及范围最大；基本图显示冰雪条件对于临界密度、最大流量等参数影响较大；冰雪条件下的亚稳回滞现象不明显，未出现换道频率局部最大值。

Cellular Automaton Model for Traffic Flow under Ice and Snowfall Conditions

A single-lane and a two-lane urban microscopic traffic flow models are developed under ice and snowfall conditions based on cellular automata. Drivers prefer to reduce speed and keep larger vehicle spacing for safety on ice and snowfall road. According to this phenomenon, this paper considers the cellular size and introduces speed factor and spacing factor which are different under different ice snowfall conditions. By numerical simulation, the curve diagram is obtained between velocity, density and flow in both normal and snow weather, and it analyzes the effects of different snow conditions on the traffic flow. It is found that the fluctuation range and level of vehicle speed in moderate snow is the maximum. Fundamental diagrams show that the ice and snowfall conditions have great influence on the critical density, maximum flow and other parameters. Metastable hysteresis phenomenon is not obvious, and the maximum of changing-lane frequency does not exist under ice and snowfall conditions.