Research On Urban Road Interchange Optimal Design

As the switching node of different direction of traffic flow,urban interchange plays an important role in ensuring the road network’s fast,efficient and safe operation.Reasonably determining the type and construction standard of interchange has become the foundation of performing the project’s function and arranging investment reasonably.In this study,the optimal design of urban interchange will be researched to provide science basis for interchange construction.Firstly,the problems along with the interchange’s development of recent years,such as choice of interchange types,determination of construction standards and scale,were discussed after a review of domestic and overseas interchange development.The interchange’s function was introduced from the aspects of traffic and service.Then the types of interchange were re-divided and the applicability of each type of interchange was analyzed.After that,the concrete content and procedure of interchange type selection were also presented after illuminating the factors influencing the choice of interchange types from the aspects of traffic,economy,environment,and landscape.The methods of traffic volume survey were studied and the principles of tr affic volume forecasting were presented.Then Multiple Linear Regression Method and Time Series Method were proposed to forecast the volume of interchange mainline,and Four Step Method was put forward to predict the volume of the crossing road.Frator model was used to calculate the turning volume.In addition,the optimal design procedures of horizontal alignment,vertical alignment,and combination alignment of horizontal and vertical were determined,and the traffic characteristics and capacity calculating methods for the ramp were also researched.The countermeasures for the problems existed in engineering practice were also presented.Then the evaluation methods for interchange design schemes were also discussed.The applicability of common evaluation methods was analyzed,and the comprehensive evaluation index system was established after considering the traffic function,safety,economy benefits,environment impacts and construction management.The quantitative method for each evaluation index was als o proposed.The comprehensive evaluation method combining Analytic Hierarchy Process and Fuzzy Evaluation Method was present,and the detailed evaluation procedure and steps were also showed.Lastly,a case study of interchange of Haihe passageway project in Tianjin was present.Two interchange design schemes were given after the procedure of interchange type selection,traffic volume forecasting,and alignment optimal design.The comprehensive evaluation method proposed in this study was used to evaluation the above-mentioned schemes to show the practicability and reasonability of the research results.