Layout Optimization Of Entrances Of The Beltway Based On Boundary Theory

The Beltway of the city is closely connected with the urban road network.When the entrances and exits are arranged,the connection with the trunk road,the outgoing road and the important hub should be fully considered.so that the transit,exit-entry traffic and the short-distance detour traffic will be more convenient.This paper analyzes the relationship between the entrances of Beltway and the urban road system,and makes a quantitative study on the related problems of the entrances of Beltway of the city.Firstly,the characteristics of the Beltway and its entrances and exits are analyzed in detail,and the general principles of the entrances layout are summarized.This paper introduces the common methods of planning and layout of ordinary expressway entrances,and analyzes their inadaptability in Beltway.Secondly,this paper analyzes the system boundary of the Beltway on the basis of the system boundary theory(especially the boundary shell theory),and demonstrates the inherent relationship between the Beltway entrance and its system boundary shell properties.The mathematic expressions of the properties of the Beltway boundary shells,such as boundary density,boundary shell pressure and so on,are defined.The matter element of the boundary shells property of Beltway under the ideal condition is established.Then,the method of fuzzy clustering analysis is used to divide the grade of outgoing road which may converge with the Beltway.Specify a number of scenarios by priority.Compute the approximation degree between the matter element of every program and ideal matter element,to determine the proposed layout program.This paper also establishes an index system for the evaluation of the layout program of the Beltway entrance,and compares the advantages and disadvantages of different evaluation methods,and selects the fuzzy comprehensive evaluation method to evaluate the layout rationality of the Beltway entrance.Finally,taking the Lanzhou Beltway as an example,using the layout method of this paper to plan the entrances,and using the index system established in this paper to evaluate the layout program of the Beltway entrance in Xi’an.