Traffic Assignment Model And Application In The Road Network With Congested Links

With the urban population and size rapidly growing, travel demand of residents is increasing correspondingly. Traffic congestion often occurs during the morning and evening peak time. Under the influence of the rain and snow or other adverse weather, it is also likely to cause a large area of urban congestion. Traffic congestion has become a common problem of cities all around the world, which affects the healthy development of the city. The important work about traffic infrastructure construction and design is the plan of urban road network. The effective planning for urban traffic organization and management can provide reasonable physical basis. It can also to analyze the traffic assignment in the road network with congested links. The problems of traffic congestion can be effectively solved though the planning stage.The static congested traffic assignment model is constructed to overcome the flaw that the traditional traffic assignment model cannot effectively depict drivers’route choice behavior under congested traffic condition. The influences of traffic congestion on traffic assignment are also discussed. This paper takes the link and road network as the research objects, based on the traffic characteristics of the road and fundamental diagram method to make a study. The main contents of this study are as follows:Firstly, the concept of traffic demand, running and delay volume are put forward based on the congestion of the real road network. The impedance function under smooth and congested link is built based on the velocity-density linear relationship model. It can overcome the traditional function’flow which couldn’t reflect the process of link from smooth to congested. Then, the congestion-delay mechanism, which is applied when the traffic demand of a link exceeds its traffic capacity, is also put forward to describe the effects of traffic congestion on traffic assignment. Subsequently, the static congested traffic assignment model is constructed based on incremental assignment and successive average method.Secondly, this paper takes the road network as the research object to analyze macroscopic fundamental diagram (MFD) based on the relationship between volume, speed and density of links. The impact of different number of O-D pairs on network-wide traffic flow characteristics is analyzed based on network transformation algorithm. The distribution ratio of O-D pairs is got when the road network in the optimal state.Finally, this paper analyzes the application of models based on traffic flow characteristics with congested links. According to the traffic location theory, this paper defined the location and minor links to analyze the advantages and disadvantages of location theory under different state of road network.