Study On The Characteristics Of Multi-Lane Traffic Flow Considering CACC Vehicles’ Cooperative Driving Strategy

In this paper,focus on the heterogeneous traffic flow mixed with adaptive cruise control(ACC)vehicles,cooperative adaptive cruise control(CACC)vehicles and manual driving vehicles,a four-lane traffic flow model considering the cooperative driving strategy of CACC vehicles is proposed by using the cellular automata traffic flow model.Numerical simulation and theoretical analysis are carried out,and the nonlinear characteristics of traffic flow are studied.Furthermore,considering the character difference of drivers and truck mixing,the four lane cellular automata traffic model is modified and deepened.This will be served as the preliminary research for the cooperative driving strategy study on the multi-lane system considering autonomous vehicles with vehicular networking available.The paper consists of the following three main parts.(1)A four-lane cellular automata traffic modeling framework is proposed to simulate the heterogeneous traffic flow mixed with ACC vehicles,CACC vehicles,and manual driving vehicles.The longitudinal position updating rules for CACC and ACC are set up based on the car-following models proposed by PATH laboratory of University of California,Berkeley.The R-MCD traffic flow model is used for the longitudinal position updating rules of manual driving vehicles.And three types of cooperative driving strategies are proposed,which are reflected in the lane-changing rules,i.e.,the baseline lane-changing rules,the promoting string strategy and the managed lane strategy.The nonlinear characteristics of four-lane mixed traffic flow under these three cooperative driving strategies are studied.The numerical results show that the proposed cooperative driving strategies are effective to enable CACC to be assembled into strings.And the mixed traffic flow shows different properties in terms of capacity and traffic congestion when different cooperative driving strategies are adopted.At the same time,the increase of CACC penetration could effectively alleviate traffic congestion and improve traffic capacity and stability.(2)On the basis of the above proposed model,a four-lane traffic flow model considering driver’s character difference is proposed.The drivers who control automated vehicles are classified into adaptive and inadaptive drivers,and the drivers of manual vehicles are classified into aggressive and cautious drivers.The drivers’ character difference is embodied in the vehicle position updating rules and the lane-changing rules.The influence of drivers’ character difference on cooperative driving strategy of CACC strings and traffic capacity is analyzed,so as to reveal the important influence of drivers’ character difference on the nonlinear characteristics of mixed traffic flow.Numerical results show that the cooperative driving strategy of CACC would work better and the traffic capacity enhances with the increasing of the adaptive drivers.On the other hand,with the increasing of the aggressive drivers,the vehicle clusters and stop-and-go waves occurred more frequently,thus the traffic capacity decreases.It can be found that the drivers’ character difference do affect the nonlinear properties of mixed traffic flow.And it indicates that the mixed traffic flow shows different properties in terms of capacity and traffic congestion when different components of drivers’ character are involved.(3)A four-lane traffic model mixed with ACC / CACC vehicles is proposed under the open boundary condition,in which the manual driving vehicles,ACC and CACC vehicles are all divided into two parts: cars and trucks.The characteristics of these different types of vehicles are reflected in the vehicle position updating rules and the lane-changing rules.The influence of truck mixing on the cooperative driving strategy of CACC platoon and traffic capacity is analyzed.The numerical results show that the capacity and the ratio of CACC integrated in strings decrease with the increase of truck mixing rate,and the influence of CACC trucks on the capacity and the ratio of CACC integrated in strings is greater than that of manual driving trucks.It is difficult for CACC vehicles to form large-scale platoons under limited road length.In addition,with the decrease of the vanishing probability of vehicles on the right boundary,i.e.the increase of the density,the average platoon length of CACC vehicles will increase when there is no truck,while the result is just the opposite when there is truck mixing in.According to the different mixing rate of CACC trucks and manual driving trucks,the managed lane strategy is proposed for trucks aim to improve the traffic capacity.