Study On The Congestion Characteristics And Control Methods On Complex Traffic Network

Currently, the congestion characteristics and control methods on urban traffic network are one of subjects collectively focused by domestic and overseas academe. On the basis of the existing research fruits, this dissertation systematically researches into a series of issues on this subject with the support of complex network theory and computer simulation, mainly including: evolving model for urban road networks, evolving model for trip networks, cascading failures on urban traffic networks, and control methods of traffic network congestion. The main research contents of this dissertation are listed as follows:1. Complex network theory was introduced into the research of congestion characteristics on urban traffic networks. A bi-level network model was established based on analyzing the characters of urban traffic network, in which the lower level represented road network and the upper level represented trip network. This work can provide a completely different research idea and direction from the existing researches.2. An evolving model for urban road network was built through abstracting network by means of primal approach. The result of the simulation model, which was done with Matlab7.0, shows that, urban road network could have a small average path length and a large clustering coefficient at the same time, proved to be a typical small-world network. Then, the responsive changes of the average path length, clustering coefficient, and average degree under the variant profit value were discussed, and the reasons were analyzed.3. An evolving model for scale-free network based on travel choice was built, and the three special cases in this model were listed. The evolution process of urban resident trip networks was simulated numerically, and the expression of degree distribution exponent was obtained by using the mean-filed theory to show the same result as the simulation result.4. Taking a two-dimensional grid with 100 nodes as road network, according to all-or-nothing model the flow assignment was done. Four basic parameters such as average load, standard deviation ect were introduced. Subsequently, the alteration of flow distribution and total system cost was compared through changing the structure of trip network.5. A cascading failures model was built after proposing the definition of cascading failures on urban traffic networks. The effects of network topology, vehicle generation rate, intersection capacity and network scale on the critical value of congestion transition were analyzed through computer simulation. The network was divided into three states (free flow, next to congestion and paralysis) by means of the derivative of arriving number with respect to time and the corresponding interval value was given.6. On the basis of cascading failures model on urban traffic networks, two parameters was introduced, which are the ratio of reconstructive node's number to the whole network(expressed by a) and the added proportion of intersection capacity (expressed by b). The core problem of increasing the traffic supply to alleviate traffic congestion was analyzed trough computer simulation, and the optimum combination of the two parameters mentioned before was obtained, a=0.04, b=0.5.7. Taking the investment of improving public traffic service level and restricting individual traffic as the two order parameters of the system, the evolution model of urban passenger traffic structure was built. By means of analyzing the model from four aspects, the evolving laws were revealed and the focus of management was pointed out.8. An influence Model of duration of traffic congestion was established through changing the cyclic Condition in the cascading failures model. By means of computer simulation, the greatest control value of traffic congestion duration under different control objectives was obtained.9. Finally, the main conclusions and creative points are summarized and the further directions are also presented.The above-mentioned contents and achievements provide a new methodology of alleviating congestion on complex traffic networks, and have very important significance in theoretical reference and practical guidance for traffic plan and management.