Key Optimization Technology Of Urban Expressway Interchange System

Urban expressway interchange is an important part of urban expressway network. Itnot only connects the urban expressway network and other urban road network,achieving road grade transition, but also affects the benefits of urban expresswaynetwork directly whether it is arranged rationally or not. The optimization technologyson urban expressway interchange system are researched to resolve traffic problembecause of indefinite hierarchie, unreasonable planning and imperfect function.The key optimization technologys are analysed on the basis of literature review,urban traffic flow characteristics and urban expressway layout.(1) The functions of urban expressway interchange on inner ring, middle ring andouter ring are determined with analyzing the classification and hierarchies. Theaffecting factors, merits and faults of different type are sunmmarized to concludespecific scope of application.(2) The planning principles such as comprehensiveness principle, coordinationprinciple, advancement principle, systemic principle, effectiveness principle andsustainable development principle are proposed based on major affecting factor. Thenode important degree method is used to plan urban expressway interchange based onturning volume, straight volume, plot ratio, the lane number of intersected roads asevaluation index and the weight way combined variable weight and information entropytheory.(3)The lengths of acceleration lane and deceleration lane under the condition ofdifferent grade and longitudinal gradient are determined on the basis of distancecompositions of urban expressway interchange. Clear distance of urban expresswayinterchange is studied with differential method considering the variable critical gap of merging behavior on urban expressway. The minimum distances between hub grade andhub grade interchange, hub grade and service grade interchange, service grade andservice grade interchange are proposed reasonably on multilane urban expressway.(4) A new method based on matter element analysis theory and information entropytheory is presented to evaluate urban expressway interchange. First of all, evaluationindex system of urban expressway interchange is established on the basis of influencefactors. Secondly, information entropies, correlation functions and matter elements arecombined to model urban expressway interchange. Finally, the model is solved on thebasis of determining each index weigh by relational entropy to optimize siteplanning.The tested result shows that the model is simple and practicable if theinterchange scheme design is reasonable or not.The correlation theories and methods in site flanning of urban expresswayinterchange are synthesized and developed, successful experiences are provided withthe theoretic importance and practice value.