| With its fast speed and large flow,expressways become the skeleton of road network in many metropolises and megacities.For expressway control,ramp metering is the main and most effective way.However,many urban expressways in China are located in the central urban area and closely connected with other urban roads in the city.On-ramp metering which is not consider the traffic demand of upstream intersection may lead to congestion of general roads.Lacking of consideration for traffic conditions of downstream intersection is likely to lead to the off-ramp queue is too long to affect the normal passage of the mainline.Therefore,the ramp and its adjacent intersection should be regard as an integrated system.Research on coordinated control of expressway to improve regional traffic efficiency and achieve the goal of fairness is the basic requirement of urban expressway management.The development of cooperative vehicle infrastructure system(CVIS)has provided new technologies and methods to further improve the efficiency of roads,but it mainly focuses on the general urban roads including intersections.In the merging area of the continuous traffic flow,establish rules for the purpose of reducing vehicle conflicts and improving efficiency are studied.It is applicable to expressways and urban expressways that keep a certain distance from the general roads.It has not yet involved ramp and its adjacent intersection as an integrated system.Based on this,the coordinated control strategies of urban expressway and its adjacent intersection under CVIS were provided to satisfy different traffic demands,so as to improve regional efficiency and provide decision support for traffic management and control.The main work can be summarized as the following aspects:(1)The analysis of urban expressway and its adjacent intersection under CVIS.Analyzing the changes of driving behaviors and traffic flow characteristics of expressway and its adjacent intersection under CVIS,providing a theoretical basis for the coordinated control of urban expressway and its adjacent intersection under CVIS.(2)Coordinated control of urban expressway and its adjacent intersection under CVIS.The coordinated control strategies under CVIS were provided in order to satisfy different traffic demands.Under high saturation,a decentralized lane-changing of mainline adaptive control method is proposed and used for the subsystem of on-ramp and its adjacent intersection,where the lane-changing rules are obtained according to the densities of different lanes in merging area and the phases and their sequence are obtained in order to maximizing the mainline flow.A speed guidance of mainline adaptive control method is proposed and used for the subsystem of off-ramp and its adjacent intersection under overfull queue situation,where the speed guidance strategy is obtained according to the destinations of vehicles upstream of mainline and the priority of the correlated phase of off-ramp is obtained in order to match the demand and capacity of the off-ramp.(3)Establishment of cellular automata model(CAM).According to the actual road conditions and the changes of driving behaviors under CVIS,improved rules of vehicle operation to establish a CAM for coordinated control of urban expressway and its adjacent intersection under CVIS.Through investigation and simulation,the model is verified and the parameters are modified.(4)Simulation experiment.Urban expressway and its adjacent intersection are used as the studied object.Coordinated control under CVIS is compared with the non-coordinated control,traditional coordinated control,adaptive control for intersection under CVIS respectively.Total travel time,flow and queue length of ramp are compared to verify the effectiveness of the proposed this control method. |
