The Research On Spatial Layout And Traffic Organization Of Urban Viaduct Access Area

In order to meet the city's growing traffic demand,many cities in our country build viaducts on the municipal road so as to make the traffic flow spatial separate and improve transportation efficiency.At present,there is a lack of the research on this kind of viaduct and related specification,and actual operation in the process of the viaduct has exposed a series of traffic problems.The paper defined urban viaduct fall-ramp location sections as urban viaduct access area.Spatial layout method and traffic organization strategy of urban viaduct access area are the main research contents.Firstly,according to the traffic characteristics of the city viaduct access areas,the city viaduct access area was defined.Then the access area road function and vehicle operating characteristics in access area were analyzed.Secondly,different vehicle lane changing behaviors in urban viaduct access area were analyzed,and entrances spacing factors in access area were analyzed.Through the analysis of the vehicle lane changing preconditions and lane changing process,based on the theory of probability formula,vehicles lane changing success probability and range of the relational model was built,urban viaduct access area entrances'spacing recommended value was given,and different types of inward and outward minimum distance of the urban viaduct access area were obtained.Thirdly,urban viaduct access area space layout principles were put forward and access area spatial layout scheme influence factors were listed based on the relevant planning road network design.Three stages space layout selection method of urban viaduct access area was proposed.At first,space layout alternatives to access area was designed based on urban viaduct access area entrances' safe distance recommended value in the first stage.Then spatial layout alternatives were simulated through the vissim traffic simulation software in the second stage.At last,composite element method was adopted to make unified program evaluation and determine the optimal layout scheme in the third stage.Fourthly,corresponding solutions to traffic organization problem of urban viaduct access area were proposed from the level of road.In order to improve the efficiency of U-turn vehicles,the waiting area was set through using space reasonably under the viaduct.Bus stations were organized so as to reduce bus stop time.Grade-separated pedestrian crossings were set to serve the slow traffic.The different traffic users' travel efficiency in access area was improved.Then the feasible scheme were proposed of accesses' traffic organization in the access area.Finally,Longyao-Sierting viaduct access area in the Fuzhou second ring road was selected as case analysis to test the urban viaduct access area space layout plan in the paper was better than the original plan.The urban viaduct access area space layout plan in the paper helped to improve traffic safety and efficiency in urban viaduct access areas and had a certain application and the value of further study.Based on the access area traffic operation characteristics and basic principle of probability theory,the lane changing probability and vehicle safety distance model of access area was established to get inward and outward spacing recommended value of access area.Based on the value,urban viaduct access area spatial layout method was put forward.Traffic organization strategies were optimized to improve the traffic operation in access area.With the simulation analysis,feasibility of the research results in this paper was verified.