Study Of The Impact Of Urban Passenger And Freight Transport On Traffic Congestion Based On Sysrem Dynamics

With the combined increase of the population of the city and the continuous growth of residents' income,the demand for passenger transport in social,recreational,commuting and other areas is rapidly increasing.At the same time,the express delivery services and commercial supermarket delivery services that meet the needs of urban residents are also increasing.The traffic congestion caused by urban passenger and freight transport had become one of the bottlenecks that restrict the overall development of cities.The urban passenger and freight transport system is a complex,non-linear and dynamic development system that is affected by many factors such as population,economy,resources,environment,and transport(including traffic demand,traffic supply,traffic operation and traffic management).Traditional quantitative statistics methods cannot describe the dynamic behavior feedback within the system.System Dynamics(SD)can not only deal with the complexity of the system,but also express the system behavior in the form of dynamic feedback.It has unparalleled advantages when used to deal with high-order and multiple-feedback complex system problems.As previous studies often overlook the impact of urban freight on traffic congestion,this paper took the urban passenger and freight transport system as the research object and used SD theory to divide the urban passenger and freight transport system into urban development module and urban traffic module.This paper used the Interpretative Structural Modeling(ISM)method to determine the interaction mechanism of subsystems and adopted Partial Least Squares Regression(PLSR)method and general linear regression method to design the structural equation of the model.With the purpose of studying the formation mechanism of urban traffic congestion,this work constructed the traffic congestion SD model of urban passenger and freight transport from the macro point of passenger and freight transport and microscopic view of travel mode choices.Based on the Vensim PLE platform,Beijing was taken as an example for simulation.Through comparison and analysis of the simulation results under the eight kinds of traffic scenarios,relevant suggestions for blockage prevention were proposed to provide decision-making reference for the effective control of urban traffic congestion problems.The main work and research results of this paper are included as follows:Firstly,from the perspective of system theory,this paper analyzed the problem of traffic congestion in urban passenger and freight transport.Combining the influencing factors of urban passenger and freight transport under the development of the new era,the impact variables and boundaries of the system were systematically analyzed.The ISM model of impact variables was constructed through structural analysis,and the interaction mechanism of each subsystem was clarified.Then,based on the causal loop diagram of the main variables that the traffic congestion system caused by urban passenger and freight transport,the PLSR method was used to forecast the demand of urban passenger and freight for solving the multiple correlation between variables.With the general statistical regression methods,the structural equations of system variables in other subsystems were determined.Finally,a traffic congestion SD model for urban passenger and freight transport was built and parameters such as calibration data and conversion data were set.Based on the Vensim PLE simulation platform,Beijing was taken as an example to analyze the stability,effectiveness and sensitivity of the model.By simulating eight different traffic scenarios,the simulation data of the relevant variables in the urban development and urban traffic modules before and after the adjustment of traffic management policies were compared and analyzed.The results showed that,the SD model based on urban passenger and freight transport can better express the changing rules of traffic congestion,the influence of urban freight transport on traffic congestion cannot be ignored,and it should be placed on the same important position as urban passenger transport.On this basis,it was proposed that the problem of urban traffic congestion can be effectively mitigated by reasonably controlling the vehicle ownership,improving passenger and freight travel accessibility,encouraging passengers to share passenger travel and freight resources.