Research On Evaluation Of Urban Road Junction Planning Based On Road Function Analysis

In china, traffic congestion in many cities largely results from the reason thatsystem structure of road resources didn’t adapt to multi-level traffic demands. Thedesigners paid more attention to the expansion of the road network facilities andignored improving the structure of the road network. In that case, it will cause thedisorder of road function. For the function hierarchy of the road network, eachclassification plays different function during the traffic flow distribution. It meansthat traffic flow is collected orderly from low level to high level roads, and isevacuated orderly from high level to low level roads. It is proposed clearly in theCode for Design of Urban Road Engineering CJJ37-2012that urban roads accordingto their importance, transportation function and service function in the network can bedivided into four levels, i.e. expressway, arterial road, minor arterial road and localroad. Each classification has its own different characteristic from other classifications,so at the network level, each road class should be connected properly according todifferent levels of traffic demands for the requirements of road function, which is theimportant composition part of the urban road network planning. It can ensure trafficflow distributes orderly among different classifications, and make the road networksystem achieve the best expected function. At present, the study on the urban roadjunction planning is relatively few, whether it is in the stage of urban comprehensivetransportation planning or in the stage of special planning for urban road network.Moreover, the study about quantitative evaluation of urban road junction planningbased on function analysis is especially lacking.The study is supported by National Nature Science Foundation Program ofTechnical Evaluation and Decision-making by Stages of Urban Road Traffic SchemeBased on Function Analysis (Program Number:51278468). Monte Carlo simulationbased on probability theory is used to study the evaluation methods of urban roadjunction planning which is on the basis of function analysis. The purpose of the studyis to provide decision basis and theoretical reference for urban road networkconstruction and renovation planning. Firstly, the paper proposes the following views: the urban road network systemshould regard the completion of traffic mobility function of the road network as animportant target during the stage of urban master planning and comprehensivetransportation planning, while in this stage there are three road classes,i.e.expressway, arterial road, minor arterial road. And the local roads should becomplemented to realize the service function of road network during the stage ofspecial planning for urban road network and regulatory detailed planning, Thecorresponding planning scheme should be evaluated depending on above views aswell. Meanings of the traffic mobility function and the service function are defined inthis paper.Secondly, the problem about leapfrog cross during the urban road networkjunction planning is analyzed, which is non-adjacent levels of road connected. TheMonte Carlo simulation method based on probability statistic is used to combine withthe calculation of system reliability, in order to study the evaluation methods of trafficmobility function in the stage of urban master planning and comprehensivetransportation planning, and service function in the stage of special planning forurban road network and regulatory detailed planning. Then the simulation testing andsensitivity analysis are carried out for leapfrog intersection. The results show that theleapfrog intersection in the urban road network will reduce the traffic mobilityfunction of road network system, and the incomplete branch network system willreduce the service function of road network.Finally, a road network system of an area in Zhengzhou city is taken as anexample. The proposed methods above are used to evaluate the traffic mobilityfunction of the arterial road network and the service function of the regional roadnetwork system; the road configuration and network density are used as constraint toput forward reconstruction plan in different stage of the road network, which canimprove the traffic mobility function and the service function of the regional roadnetwork.