Study On Regional Road Network Perimeter Control Based On MFD

With the development of urban economy,the vehicle number increased,regional traffic congestion often occurs in urban road networks at peak times.Oversaturated road network increased travel time and reduced service quality.Some existing urban road network control strategies need to be complicatedly mathematically modeled for large scale regional traffic congestion in macro road networks,making it difficult to apply these strategies in practice because it is difficult to obtain accurate OD distribution data of the road network.However,MFD is an intrinsic property of the road network and exists independently of traffic demand.It does not need complex OD data of the road network and is suitable for short term and large scale traffic operational state determination.This paper makes use of this feature of MFD,and puts forward the research method of regional network perimeter control based on MFD,which mainly includes the following three aspects.(1)As an objective sub-network in boundary flow control,MFD with high fitting degree and compactness is its first premise.Firstly,this paper analyzes the basic theory of MFD,combs its basic properties,relevant characteristics and applications,and then divides the road network into a plurality of homogeneous sub-regions,chooses the congested sub-network with the optimal fitting degree MFD as the objective sub-network in boundary flow control,so as to determine the area boundaries of the perimeter control,the closed boundary of the network as the controlled area,and then analysis MFD characteristics of the controlled area,according to the traffic flow conservation law to establish the flow equilibrium equation in the region,and finally identify traffic operational state of the controlled area with the help of MFD curve change rules.(2)In this paper,the weighted flow of vehicles in controlled areas is the most important control target.A perimeter feedback control strategy is proposed for the controlled area.Boundary control constraint condition and regional control model is established by considering the storage team capacity of the upstream section of the boundary intersection.This paper maintains the accumulated number of vehicles in the controlled area near the optimal threshold to ensure that the controlled area is concentrated on the left half of the MFD,always remains the state of efficient operation and not affect the operation efficiency of the road network outside the border.(3)In this paper,the actual road network is used as the research object to validate the effect.According to the output of Vissim simulation,the MFD cubic fitting curve of the controlled area is established by Matlab software,and the related parameters of the MFD in the controlled area.Then this paper comparatively analyzes the indicators of the controlled area under no-boundary control,deterministic boundary control and extendable boundary control respectively,and the simulation results under three different strategies are given.The results show that the implementation of the scalable perimeter control strategy proposed in this paper can significantly improve traffic indicators in the road network and effectively reduce the number of stops and queue length at the border intersections,and solve the problem of queuing too long or even back overflow to the upstream intersection problems.