Research On The Guidance Method Of Urban Traffic District Based On MFD

With the acceleration of the urbanization process in China,the number of cars has increased year by year,resulting in an increasing number of vehicles in the urban road network and a serious traffic problem.The lack of transportation infrastructure and effective traffic guidance have exacerbated the congestion of urban traffic,making it no longer just congested at a certain intersection or road,but developed into a regional traffic congestion.As an important induction method widely used in the field of transportation,the variable information sign is mainly used in the transmission of community induced information,and has been widely used in large and medium-sized cities in China.This paper uses VMS,combined with fuzzy PID controller,to study and establish a guidance strategy based on macroscopic fundamental diagram to improve the efficiency of urban traffic guidance.Firstly,to meet the demand of traffic induction and reduce the complexity of traffic network,the improved Newman fast algorithm is used to divide the divisionl.According to the principle of homogeneity,the number of lanes,the number of vehicles and the length of lanes are selected as the calculation indexes of edge weights.According to the theory of community contribution degree,the division is calculated by calculating the contribution degree of the community to improve the efficiency of dividing the traffic community.The experimental results show that the divided traffic districts have good homogeneity.Secondly,fuzzy control is used to adjust the parameters of PID controller,which is difficult to adjust and can not be adjusted in real time.Based on the incremental PID control model,the traffic induced control model is established.The controller takes the total number of vehicles expected in the community as the input index of the control system,the actual total number of vehicles in the community as the output index of the system,and the traffic volume entering the community as the control variable.Establish fuzzy self-tuning rules for three parameters Kp,Ki and Kd of PID controller.The membership function and fuzzy inference rule in fuzzy controller are determined.Finally,the three control parameters of PID can be adjusted.Finally,the influence of traffic inducement on the macroscopic fundamental diagram is analyzed.In the oversaturation stage,the traffic guidance has a more obvious effect on the macroscopic fundamental diagram.The total number of vehicles in the community and the number of vehicles out are selected as variables to construct the macroscopic fundamental diagram,and the induction strategy based on the macroscopic fundamental diagram is established.Combining the theory of macroscopic fundamental diagram with the fuzzy PID control,the traffic area is taken as the unit of induction.Taking the number of vehicles running in the community as the judging index,the flow rate at the entrance of the community with crowding is induced.And VMS is used to release the induction information of the recommended bypass.The simulation through Vissim simulation software verifies the effectiveness of the induction strategy.