MFD对车型构成的敏感性分析及车辆换算系数计算方法

Effects of Mixed Traffic Flow on Macroscopic Fundamental Diagrams and Its Application to Analysis of Passenger Car Equivalent

针对车辆的换算系数,现有研究较多集中于静态车辆换算系数,但静态车辆换算系数无法准确描述拥挤状态下车辆间的交互影响,未充分考虑车辆在不同交通状态下相互作用的动态变化对车辆换算系数取值的影响。为了能够适应动态交通的演化,以棋盘式路网为研究对象,利用宏观基本图(Macroscopic Fundamental Diagram,MFD)分析了宏观基本图曲线对大型车比例的敏感性,并针对不同的交通状态提出了相应的车辆换算系数计算方法。首先构建路网微观仿真模型,利用微观仿真试验证实了路网宏观基本图的存在;然后根据仿真数据采用分段函数拟合MFD曲线,通过改变大型车的比例设计多组仿真试验,并绘制出不同大型车比例下的MFD图形,分别从定性和定量2个层面分析宏观基本图曲线对车型比例的敏感性;最后根据敏感性分析结果,利用宏观基本图提出了一种针对不同交通状态的车辆换算系数计算方法。结果表明:当路网处于非拥挤状态时,对应于MFD曲线的上升段和持续段,车辆换算系数取值仅与大型车比例有关;而当路网处于拥挤状态时,对应于MFD曲线的下降段,车辆换算系数取值不受大型车比例的影响,其仅与路网存在车辆数有关。所提方法和思想为理解车型构成对路网交通状态的影响提供了新思路,有助于为交通规划和管理部门提供政策支撑。

Previous studies have focused mostly on static passenger car equivalent（PCE）and showed that static PCE cannot accurately describe the interaction among vehicles in a crowded state.They did not consider the influence of the dynamic interaction among vehicles in different traffic states.To estimate the PCE according to the traffic state of a network dynamically,thisstudy employed a macroscopic fundamental diagram（MFD）to analyze its sensitivity to the proportion of heavy goods vehicles（HGVs）on roads based on the checkerboard road network.This study also proposed a method to calculate the PCE of HGVs under various traffic states.First,the road network simulation model was constructed and the MFD was defined and verified using microscopic simulation.Secondly,the MFD of the network was modeled using apiecewise linear function according to simulation data,and multi-group simulation experiments were designed with changes in the proportion of large cars.Changes in the MFD shape along with various proportions of HGVs were studied.The sensitivity of the MFD to HGV proportion was analyzed qualitatively and quantitatively.Third,a method to estimate the PCE of HGVs under different typical traffic states based on the MFD was presented.The proposed PCE formulation indicates that the PCEs of HGVs are related to the proportion of HGVs under uncongested conditions,which corresponds to the rising section and continuous section of the MFD curve.When it is related to the number of vehicles in the network（or density）under congestion,it corresponds to the falling section.The method and insights proposed in this paper provide an understanding of HGV influence on the network traffic state,as well as provide support to transport planning and operation.