Research On Capacity Of Road Network

In this dissertation, capacity of road network is studied.Road network is made of road sections and intersections. The determining of capacity of road network not only can provide transportation plan and management with basic data and measured evidence, but also it is one of necessary parts for consummating the theory of traffic engineering. Further more, no method can computer the capacity of the road network hitherto. So it is very meaningful to research the capacity of road network.According to the literature about capacity of road network, there exist several methods for studying capacity of road network in the world, namely Time and Space Consummation Method, Linear Planning Method, Cut Set Method, Traffic Assignment and Simulation Method, Special Capacity Method, and Providing and Analyzing Method. And there are two kinds of conception explaining the capacity of the road network. One is the ability passing the road network, that is, the result of the conception is the sum of the number of vehicles passing several key sections in one hour, and the other is the number that vehicle can be served by the road network in one hour. On the previous research, traffic characteristics on the road network is analyzed, the minimal length used for studying capacity of road network and the main factors influencing the capacity of the road network are determined in this dissertation. Considering the conception of capacity of road section, a new definition of the capacity of road network is made. The new definition is made of two parts: the definition of ideal capacity of road network and the definition of real capacity of road network. Each is defined as follows:Definition of ideal capacity of road network: under the ideal road and traffic condition, every traffic individual chooses his (or her) path whose cost is minimal. Only if there is road on the road network, there must be traffic individual traveling on it. Under reasonable condition, the number of traffic individual served by the road network in unit time.The definition of real capacity of road network: on the basis of the definition of ideal capacity of road network, adjusting what is not consistent with ideal road, traffic condition, and behavior to choosing path, and the matching degree of road network distribution, and so on. The result is real capacity of road network.On the basis of the new definition, contrasting all kinds of methods about theory, arithmetic and the degree studying the capacity of road network, "Time and Space Consummation Method" is adopted in this dissertation, a generalized model is made, parameters needed to be studied are also determined. Because these parameters can be gotten only by investigating site data on a large scale, and veracity of these data is suspected hitherto, the key processes are to determine these parameters from theory point.According to the result of analyzing track that each traffic individual travels in the all kinds of intersections, effective traveling space on each class road is determined. Then effective traveling time provided by each intersection in one day is researched. At last, under the ideal condition, the model of time and space resource provided by the road network in one day is made.The theory of optimization and car-following are adopted to determine the relationship between traveling speed and headway in this dissertation, and a model about critical speed is made. Moreover, introducing the geographical positional system to collect traffic data, I applied critical speed model to compute critical speed on Beijing road network, on the ideal stage.Then, stochastic theory is applied to make average traveling time model, under the ideal condition. In order to using expediently the model, the computing step and flow-chart is also given.At last, under the ideal condition, the model computing capacity of road network has been made. After contrasting ideal with real condition, the factors needed to adjust and the adjusting methods respectively are determined, the real capacity of t...