| With the rapid development of China’s social economy,the number of motor vehicles in China has surged rapidly.In addition,due to the unreasonable ratio of road network level and uneven distribution of traffic flow,urban road network traffic congestion and low operating efficiency are becoming more and more serious.How to quickly and accurately identify the efficiency and performance of urban multilevel road network,so as to find out the crux of the problems such as low efficiency of road network operation,which is a subject worthy of further study.The research content of this paper mainly includes the following items:(1)The multilevel road network and traffic characteristics are studied.This paper expounds the definition of multilevel road network,taking the main urban area of Chongqing city as an example,analyzes the traffic characteristics of multilevel road network and the influencing factors of the road network characteristics.(2)The system of multilevel road network efficiency and performance evaluation index is constructed.This paper expounds the design principle of the evaluation index system,and proposes to identify the network efficiency and performance from the three aspects of road network capacity,operating efficiency and network reliability.This paper introduces the application environment and influencing factors of the basic characteristic theory model of MFD,and proposes a new MFD theory model for network efficiency and performance evaluation.Based on the characteristics of road network MFD,the evaluation indexes of road network capacity,operating efficiency and network reliability are selected to establish an evaluation index system of road network efficiency and performance based on MFD.(3)An MFD modeling method for multilevel road network efficiency and performance evaluation.The simulation road network is constructed by VISSIM,and the required data is obtained by simulation experiment.It is proposed that K-Means is used to cluster the data,and least square method is used to fit the data,so as to obtain a more accurate piece wise MFD function.Finally,the process of network efficiency evaluation from three aspects of network operating efficiency and network reliability is described in detail.(4)Road network efficiency and performance evaluation based on MFD.The characteristics of MFD of urban multilevel road network are carefully analyzed,and the traffic flow density corresponding to the falling section of road network MFD is used as the evaluation index of road network capacity.The operating time of the road network when the carrying capacity of the road network reaches the descending section and the density range and time range corresponding to the stationary section of the MFD are used as the index to identify the operating efficiency of the road network.The discrete time and density stability indexes of road network operation efficiency were used as road network reliability evaluation indexes.The efficiency and performance of each road network was identified,and the road network capacity,operation efficiency and reliability of the road network were found to be influenced by the capacity of intersections and the ratio of road grades.(5)The road network near Xuefu Avenue in Nanan District of Chongqing was selected for efficiency evaluation.According to the actual survey data,the parameters are set and the simulation experiment is carried out by using the road network of VISSIM reproduction case.Compared with the design road network,the ratio of road level in the case road network does not meet the recommendations of road network planning.Moreover,due to the influence of terrain conditions,no widening design has been done at each intersection.After the failure of key sections,the reliability evaluation index of the case road network changes greatly and the reliability is low.Reasonable adjustment of the ratio of road network grade to the widening design of the intersection can improve the operation efficiency and reliability of road network carrying capacity.In this paper,a new MFD theoretical model is proposed,and an index system and method are constructed to evaluate the efficiency and performance of multilevel road network from the aspects of road network capacity,operating efficiency and network reliability,so as to evaluate the efficiency and performance of road network and provide a relatively accurate reference for traffic managers to understand and improve the efficiency and performance of road network. |
