Research On The Theory And Quantitative Method Of Urban Rail Transit Category Selection In The Planning Phase

As we all know,urban rail transit is one of the most effective ways to solve various traffic problems in big cities.With the development of industry and technological progress,urban rail transit has gradually evolved into a variety of types of categories,which have significant differences in traffic volume,driving orientation and speed.Each type of urban rail transit category has its own traffic functions,which can meet different traffic needs.The process of clarifying the function of a certain urban rail transit line in the city and selecting the appropriate category to match this demand is the selection of urban rail transit category.However,urban rail transit often has the characteristics of difficult construction and high cost.It needs to be planned in detail before construction,and the selection of mode is the most important part of the planning link.Only by reasonably selecting the mode category that meets the line positioning and requirements in all aspects can we achieve the primary goal of solving traffic problems and facilitating residents ’ travel,and guide the better development of the city on the basis of relying on the general planning of the city.Nowadays,most of the researches on the mode selection of urban rail transit in China are based on the qualitative analysis of the characteristics of various modes and the subjective selection of experts ’ opinions.There are few quantitative methods,which expose the problem that human factors have great influence on the mode selection.After accumulating the relevant data and experience in the field of exploring mode selection for many years,the original qualitative method should be improved by quantitative thinking in order to avoid the influence of subjective factors and be more objective and reasonable.Considering the complexity of urban rail transit planning and influencing factors,based on the three stages of planning,aiming at the planning content and research depth of each stage,this paper puts forward the calculation method or model of mode selection in each stage,so as to construct a systematic method of mode selection.The main research contents and innovations are as follows:(1)The theoretical framework of “three-stage-four-dimensional” mode selection is constructed,and the specific content and indicators of the four objectives in each stage are analyzed in detail with the target requirements of the four dimensions as the horizontal.Taking the planning stage of urban rail transit as the vertical direction,this paper visually compares the progress and depth of research content from the network planning to the engineering and research stage under each factor goal,so as to establish the logical framework of the full text.(2)In the online network planning stage,in order to determine the “volume +speed + service level” line combination mode as the goal,the volume level is determined in the passenger flow dimension,and the speed requirement is determined in the time dimension.In the spatial dimension,the circle structure of the urban core area,the central area,the periphery and the suburbs is divided,and the three quantitative indexes of the line space subordination,the line equivalent station spatial distribution and the line station spacing coefficient are constructed to calculate the main service area of the line,namely the service level.Thus,the method of judging the recommended formula scheme under each combination mode is given,and the feasibility of the formula is judged in the economic dimension.(3)In the construction planning stage,in order to determine the “ line combination mode + line level” as the goal,using the research results of the previous stage in space,time and passenger flow,the highest speed is determined in the time dimension.In the passenger flow dimension,the station density(ride comfort)and departure interval are concerned.In the spatial dimension,the line passenger flow and length adaptation coefficient,line level shape coefficient,line guide coefficient to urban spatial structure,line station equivalent ratio,line degree centrality value and line average distance coefficient are constructed.The entropy-grey fixed weight clustering model is used to divide the line level.Based on this,a method to judge the recommended scheme under each ’ line combination mode + line level ’ is given,the feasibility of the scheme is judged in the economic dimension,and the quantitative method to determine the vehicle type(vehicle type and marshalling)by suitability function is given.(4)In the stage of engineering feasibility study(hereinafter referred to as engineering feasibility study),in order to improve the objectivity and comprehensiveness of urban rail transit mode selection,relying on the research results of service level and line level in the first two stages,a total of 16 indicators in four dimensions of space,time,passenger flow and economic benefit are constructed,and the method of calculating urban rail transit mode scheme by mathematical model is given.In this paper,a comprehensive decision-making model of ’ CRITIC-grey association TOPSIS ’ is constructed.CRITIC method can comprehensively consider the variability of indicators and the correlation between indicators for objective weighting.Combining grey correlation analysis and TOPSIS evaluation,the concept of comprehensive proximity is proposed,and it is used to describe the difference of similarity and distance between each scheme and the ideal scheme.(5)Taking Changchun urban rail transit line 2 and line 8 as the research object,using the theoretical framework and method of ’ space-time-passenger flow ’ urban rail transit mode selection in the planning stage proposed in this paper,the mode selection is studied from the three stages of line network planning,construction planning and industrial feasibility study.The combination mode of line 2 is “large volume + general speed + central urban level”.The line grade is the main line,and the 6 B marshalling subway mode should be used,and the long-term 8 sections are reserved.The combination mode of Line 8 is “medium traffic volume + normal speed + regional level”,and the line grade is the extension line.The light rail category of 6C grouping should be adopted.The above conclusions are the same as the category selected by the two lines,and the operation effect is good.It can be considered that the theory and method of this paper are feasible and reasonable,which provides reference for the selection of urban rail transit category in the future.