基于安全车速的北京冬奥会山地道路冰雪路面通行能力研究

Capacity of Mountainous Roads with Ice and Snow Pavement During Beijing Winter Olympics Based on a Safe Speed Model

复杂山地线形和道路冰雪路面结合条件下的安全车速设置及通行能力保障是交通管理面临的新挑战。针对北京冬奥会延庆赛区复杂山地道路冰雪路面场景,建立了安全车速与道路线形设计及路面附着系数之间的关系,以安全车速为依据得到了不同路面条件下山地道路的通行能力。依据道路平曲线、竖曲线和横断面数据建立了山地道路三维空间模型;分析了车辆在山地道路平纵组合路段的受力情况,构建了车辆安全行驶速度与圆曲线半径、道路超高、纵坡坡度和路面附着系数的关系模型,并分析了基于安全车速模型的道路通行能力。为了验证模型,选取2种常见的冰雪路面状况和2种常用的车辆类型,获得不同条件下山地道路冰雪路面的安全车速。采用VISSIM软件设计了20种仿真场景,结合道路实测数据验证了安全车速模型的对山地道路冰雪路面车辆安全行驶的提升作用。实测与结果表明:相比全程单一限速模型,所建立的安全车速模型在冰膜路面的行程时间缩短了约38%(小汽车)和32%(大客车),雪板路面的行程时间缩短了约26%(小汽车)和24%(大客车)。山地道路交通流量存在1个自由流到饱和流的相变过程,冰膜路面小汽车下行最大交通量为241辆/h(单向行驶)和231辆/h(双向行驶),大客车下行最大交通量为227辆/h(单向行驶)和222辆/h(双向行驶);雪板路面小汽车下行最大交通量为319辆/h(单向行驶)和249辆/h(双向行驶),大客车下行最大交通量为301辆/h(单向行驶)和236辆/h(双向行驶)。

A novel challenge for traffic management is setting speed limits as well as guaranteeing road capacity under complex mountainous roads under the condition of ice and snow pavement. A safe speed model is proposed to solve this problem in Yanqing competition zone of Beijing Winter Olympics. The model studies relationships of safe speed, road alignment design, and adhesion coefficient, taking the safe speed as a basis to obtain the critical road capacity of mountainous roads under different conditions. A three-dimensional spatial model of mountainous road is developed by combining road horizontal curve, vertical curve, and cross section data. Based on the model, the forces acting on the vehicle in a mountainous road section of horizontal and vertical alignments is analyzed. The relationships between the safe speed and its influencing factors including radius of curves, road superelevation, downward slope, and adhesion coefficients of road is studied. The road capacity is analyzed based on the safe speed model. Two pavement conditions and two vehicle types are selected as case studies to obtain safe speeds on ice and snow pavement of mountain roads under different conditions. A total of 20 simulation scenarios are designed by VISSIM to verify the safe model. Combined with the actual traffic data, the simulation results show that compared with the traditional full speed limit model, the travel time of the developed model can reduce by 38%(car) and 32%(bus) with ice pavement;and reduce by 26%(car) and 24%(bus) with snow pavement. In addition, there is a phase transition from free flow to saturated flow in the traffic flow of mountainous road. The maximum road capacity for cars of the downward slope with ice pavement is 241 vehicles/h(one-way driving) and 231 vehicles/h(two-way driving);for buses is 227 vehicles/h(one-way driving) and 222 vehicles/h(two-way driving). The maximum road capacity for cars of the downward slope with snow pavement is 319 vehicles/h(one-way driving) and 249 vehicles/h(two-way driving);for buses is 301 vehicles/h(one-way driving) and 236 vehicles/h(two-way driving).