Study On Analytical Method Of Heterogeneous Traffic Flow Characteristics Under Connected And Autonomous Environment

When transportation systems are vigorously developed,a series of traffic problems arise.The driving behaviors of traditional drivers are limited because of their response abilities.Moreover,their differences in driving habits and driving mistakes also contribute to poor condition of traffic flow stability and frequent traffic problems.Scholars in various countries generally believe that Connected and Autonomous Vehicle(CAV)can improve traffic flow operations from the microscopic vehicular level in the connected and autonomous environment.Then CAV provides an effective way to solve traffic congestion and other problems.From the traffic engineering perspective,the study on systematic analysis method for impacts of CAV on traffic flow characteristics is helpful to provide scientific theoretical basis for large-scale real CAV implements and traffic management and control under CAV traffic flow background in the future.Therefore,this thesis aims at seeking the theoretical methods to systematically analyze the impacts of CAV on traffic flow characteristics.In this way,the methodology for characteristics analysis of CAV heterogeneous traffic flow will be achieved.This thesis is mainly composed of the following three aspects: the fundamental diagram and capacity analysis method of CAV heterogeneous traffic flow,the LWR model(Lighthill-Whitham-Richards)and Cell Transmission Model(CTM)of CAV heterogeneous traffic flow,and the analytical method of string stability of CAV heterogeneous traffic flow based on microscopic car-following models.(1)Base on the randomness of relative spatial positions of vehicles in CAV heterogeneous traffic flow,this study explores the mathematical expectation of the proportions of CACC vehicles,ACC vehicles,and human-driven vehicles.Then the function between speed and spacing at equilibrium is used to derive the fundamental diagram of the heterogeneous traffic flow mixed with different CAV penetration rates.Based on this,the study proposes the systematic method for capacity analysis of traffic flow under the background of connected and autonomous environment.Following that,control design methods of CACC and ACC system parameters are obtained,from the perspective of CAV heterogeneous traffic flow capacity.(2)This study explores the slope expression of flow-density curve of CAV heterogeneous traffic flow,based on which the theoretical calculation method of traffic wave speed in the heterogeneous vehicular flow is achieved.Then the modeling method for LWR model is proposed from the perspective of the fundamental diagram of the heterogeneous traffic flow.Moreover,focusing on heterogeneous triangular fundamental diagram,this study analyzes some key factors to present the modeling method for multi-class CTM of CAV heterogeneous traffic flow.Following that,the macroscopic traffic flow state evolution method is proposed under the large-scale CAV background.(3)Based on various model structure types of microscopic traffic flow car-following models,this study proposes the generalized analytical framework of string stability of CAV heterogeneous traffic flow.There are three generalized analytical frameworks proposed in this thesis: the analytical framework of string stability of CAV heterogeneous traffic flow based on the traditional car-following model structure,the analytical framework of string stability of CAV heterogeneous traffic flow considering acceleration feedback from the immediately preceding vehicle,and the analytical framework of string stability of CAV heterogeneous traffic flow considering acceleration feedbacks from multiple vehicles ahead.Based on the string stability analysis,control design methods are also presented to enhance string stability of CAV heterogeneous traffic flow.Meanwhile,this study also explores internal relevance between stability and traffic safety and emissions.This relevance can not only emphasize traffic engineering significance of analytical investigation of CAV heterogeneous traffic flow stability,but also have benefits in achieving the balance between theoretical investigation of stability and applications of traffic engineering.