A Study On Dynamic Link Impedance Function Of Transportation Network

In the past decade, intelligent transportation systems(ITS) have attracted much interest among researchers and practitioners. The main objectives of ITS are to improve the efficiency of transportation networks, enhance traffic safety, and reduce delays and negative environmental effects by utilizing real-time or predicted traffic information. The dynamic transportation network model, has also been regarded widely. Dynamic traffic assignment is to assignment the time to time variational traffic into different routes to reduce traveler's cost or system's total cost. The paper analyses the optimal distributing form of the traffic flow pattern to support the traffic management and dynamic route guidance under the states of the traffic supply and the traffic demand known.After analyzing the basis on the model of dynamic traffic assignment and the generic form of the dynamic link travel time function in the dynamic network model, the paper analyses and compares some discrete dynamic link impedance functions used in abroad as well as in our country, and point out their advantages and disadvantages. At last the paper brings forward a new SQ model which has queue length by utilizing the principle of distributing wave in the traffic flow theory. The model reveals the dynamic character by using the flow density as a variable. It can be used to calculate the dynamic link travel time in dynamic signalized traffic network. After the analyses by example, it can been found that the SQ model is superior to any one of the four traditional discrete dynamic link travel time models in terms of the algorithm, model calibration, model discretization, accuracy, algorithm efficiency and memory consumption.The paper programs and calculates the time-space network, and utilizes the principle of variational inequality problem, the principle of the mathematics programming, probability, traffic engineering to analyses the algorithm of the dynamic transportation network model and establish a VIP model for the dynamic traffic assignment based on the research of the production of the ITS especial in DTA at home and abroad. The paper also designs a new algorithm for the model: nested diagonalization method.