Boundary Signal Control And Route Guidance For Urban CBD Based On MFD

The complexity and difficulty of urban traffic control management is increasing because of the complexity of traffic network and traffic flow.It is meaningful that make use of the existing infrastructure and rationally redistribute the in-transit traffic flow through control and guidance strategies to reduce the time delay and parking times of the whole road network.Macroscopic Fundamental Diagram(MFD)is an important theoretical tool for characterizing the characteristics of traffic flow from the subregional level.The implementation of boundary control based on MFD to alleviate traffic congestion in protected areas is one of the popular research in current academic.The theoretical basis for implementing boundary control is the macroscopic traffic flow model.Therefore,this paper proposes to graphically express the macroscopic traffic flow model with multiple subregions by colored Petri nets.The spatial and temporal evolution of real traffic flow will be more realistic by introducing transfer flow and travel delay.More importantly,for the first time,the gated links and junctions on the border of the protected network are abstracted as so-called buffers.Based on queue length in buffer zones,a framework of boundary control and traffic flow guidance is established,which expands the current research ideas of boundary control.Moreover,a perimeter control framework integrated with route guidance is proposed for enhancing the ability of perimeter control on alleviating total travel delay out of the protected network.There are mainly three modules in this integrated framework.Firstly,perimeter control inputs are optimized by the method of model predictive control at region level.Secondly,a set of internal flow controllers are adopted to homogenize traffic density among subregions and route guidance strategies are used by monitoring the number of queuing vehicles in buffers.Finally,the proposed traffic model is served as a plant for evaluating network performances objectively.Based on the above integrated control framework,numerical simulation results show that the proposed control strategy can effectively reduce the accumulated travel time of the network and balance the accumulation in each region under the situation of large and unbalanced traffic demand.This paper alsocarries out sensitivity analysis and experience summary on the impact of buffer capacity on the overall network performance,paving the way for the application of relevant theoretical research in practice.