Study on Layout Optimization of Passenger Stationbased on Multi-objective PlanningAbstract—This paper study on the optimal layout of passenger station and the basic principle of selection location. There are both quantitative index and qualitative index existing in the evaluation indexes of the layout of passenger station. To unify the evaluation indexes, this paper establishes a multi-objective planning optimization model of the layout of passenger station, by using the basic idea of multi-objective planning and introducing the effect of targets of the evaluation indexes. In Nanning railway terminal for example, four evaluation indexes: construction investment、operation cost in railway terminal、cost of passenger trip and the other social benefits are determined. Calculate respectively all effect of targets of the evaluation indexes and then determine the optimal scheme of the layout of passenger station in Nanning railway hub by the total effect of targets after being weighted.Keywords-component; multi-objective; passenger station; Layout OptimizationIn the past, paying much attention to improving line carrying capacity and neglecting the carrying capacity of hubs or stations in China leaded to the shortage of passenger capacity and the difficulty in meeting the demand of transport market. At present, China is in the primary stage of high-speed railway construction. High-speed railway being introduced into existing railway terminal will break the transport pattern of existing railway hub and will dramatically change the original railway hub transportation structure、transportation operation mode and transportation path. It is an important question in railway terminal planning to reasonably determine the locations and the number of the high-speed passenger stations in hub and optimize the layout of passenger stations in terminal.I Layout Optimization model of Passenger Station in railway hubA. Layout of passenger station in railway hub and basic principle of selection location（1）For human-oriented, make the trip distance and time of passenger from the starting point to passenger station shortest、the travel cost lowest、the riding most convenient and reduce the passenger transfer or make it more convenient. (Includingthe transfer between one or multiple transport modes)（2）Take the market as the direction and make the benefits as the center. Passenger station in city is kind of large infrastructure. Inputs and outputs should be the standard of the evaluation of railway operation benefit. At the same time, removal expense which is relative to the selection location of passenger station 、investment of civil engineering 、completion time of project and some cost related to project should be brought into the constraint condition of selection location of passenger station. It still needs to compare the operating costs of different schemes of selection location of passenger station.（3）The development of city should be combined with the city planning. It includes urban master planning 、urban public transport planning 、urban rail transit network planning and so on. Their evaluation indexes are different. In a word, it should reflect the compatibility between railway station and the city, and guide and advance the development of the transportation of the city. [ 3 ]On above foundation of all basic principles, alternatives should be in accordance with the natural distributed discipline of passenger flow, and be beneficial to hub passenger train. They also should make full use of the railway existing equipment and the urban existing collecting and distributing centre. At the same time, they should have both good geological conditions and economic environment. B. Layout Optimization model of Passenger Station in railway hubThe economic evaluation indexes of layout optimization model of passenger station in railway hub have both quantitative indexes such as engineering investment 、operating costs and so on and some qualitative indexes which can’t be quantified directly such as cooperation with the development planning of city 、environment protection and so on. To be convenient to unify quantitative indexes and qualitative indexes, establish layout optimization model of passenger station below by applying the theory and method of multi-objective planning.1max Ii i i f w f ==∑ （1）In formula:i —Quantitative indexes and qualitative indexes of all design schemes. I evaluation indexes in all;i f —Effect of targets of all evaluation indexes （01i f ≤≤）. It is introduced for beconvenient to unify the dimension of quantitative and qualitative indexes. For the effect of targets of quantitative indexes, determine the corresponding value of zero and one, and then evaluate the value through insertion method. For the qualitative indexes, use the six-degree standard to quantify: Best —1、Better —0.8、General —0.6、bad —0.4、worse —0.2、worst —0.i w —Weight of all evaluation indexes. It can be confirmed by the means ofinvestigation and argumentation and experts. In addition,11Iii w==∑.f —Total effect of targets of all design schemes. Its value determines the finalgood or bad ranking of all design schemes.II Construction scheme of passenger station in Nanning railway hub A. Present situation and future planning of Nanning railway hubNanning railway hub is the important regional terminal in southwest railway network. At present, it is connected with three railway main lines: Hunan-Guilin line 、Nanning-Kunming line and Nanning-Fangchenggang line. The constructing line: Liuzhou-Nanning passenger dedicated line 、Nanning-Litang railway 、Yunnan-Guilin railway and Nanning-Qinzhou railway all introduced into Nanning hub. Recently, there will be Jinchengjiang-Nanning railway 、Naning-Pingxiang railway and so on introduced into Nanning terminal. At that time, the number of intersection railway lines will be nine in Nanning hub.In terminal , there’re only one passenger station—Nanning Station. It has five receiving-departure lines for passenger trains (including main line)、one freight through line 、four receiving-departure concurrently storage sidings 、four shunting lines.The population of Nanning in downtown is planning to be 69 million in 2010 and 78 million in 2020. The population of the center is planning to be below 21 million in 2010 and below 29 million in 2020.The existing layout of railway terminal is in loop mode. Affected by geological condition and features 、the limit of removal working, existing p assenger station can’t be reconstructed in large scale. All of passenger working being concentrated in a station leads large pressure to city traffic. Therefore, the layout mode should be thatdisperse several centers in different places. That needs new passenger stations to satisfy the operating demand.B. Scheme of passenger station in Nanning railway hubThe recent passenger volume in Nanning terminal is 8 billion per year and the long-term will be 17 billion per year. Affected by geological condition, Nanning station cannot satisfy the passenger demand of terminal. With the construction of south-north intercity railroad in Nanning railway terminal, the terminal passenger system will gradually form the “loop” pattern of “The main in north and the minor in south” by south -north loop line.According to the principle of selection and location of passenger station in hub, come up with three alternatives for the south-north passenger station: reconstructing Nanning station （1）、new building Nahuang station （2）、new building Fengling station （3）. [ 3 ]III Evaluation index of construction scheme of passenger station in Nanning railway terminalA. Costs of engineering investment 1zCalculate the investment of line 、demolition 、land expropriation 、bridge 、tunnels of the construction scheme of passenger station. The costs of engineering investment of all schemes are presented in table 1.Table 1 Main engineering investment of alternative stations （10 thousand Yuan ）2()2111 2JKLjkl jkl l j k l z u S λ====∑∑∑In formula:j —The number of passenger stations in hub; k —The direction in hub;l —Different trains in hub, including high-speed train and normal-speed train;jklu —The number of passengers in l kind train which is from j station to kdirection of hub;jklS —The distance of l kind train which is from j station to k direction of hub interminal;l λ—The unit operating cost of l kind train.In accordance with the cost of one person per kilometer, the operating cost of taking normal passenger train is 0.078Yuan per person in one kilometer. The operating cost of taking high-speed train-set is 0.094Yuan per person in one kilometer.For three alternative stations, the distance of different kinds of trains to each direction is listed in table 2 and the operating costs of different passenger station in hub are presented in table 3.Table 2 The shortest path of alternative stations in accordance with direction（km ）3()311 3IJij ij i j z c u ===∑∑In formula:3z —Cost of passenger going to station; iju —Total number of passengers from i district to j station for taking differentkinds of trains (including high-speed train and normal-speed train);ijc —Unit cost of passenger trips from i district to j station for taking trains.Table 3 Operating costs in hub (10 thousand Yuan)distribution of railways and rivers, Nanning can be distributed into six residents trip districts.Table 4 Costs from trip districts to alternative station (Yuan)thousand person per year)table 7.D. The other social benefits 4zBy applying the three-station scheme （1、2、3）, it is convenient to arrange the task of different stations in hub .The car flows travel smoothly in hub and it is convenient for passengers to take trains. The two-station scheme （1、2）can’t consider partial regions of the city and the contact between stations is not frequent and it is not convenient for passengers to go out.Table 6 The number of intercity passengers of trip districts (10 thousand personper year)hubA. Costs of engineering investment 1dTable 8 Costs of engineering investment（10 thousand Yuan ）11passenger station by using linear model. Supposed when 1z =520 billion Y uan, 1d equals zero and when 1z =200 billion Yuan, 1d equals one. Then layout schemes1d of all passenger stations will be evaluated. The results are listed in table 9.B. Operating costs in hub 2dOperating costs of layout schemes of passenger station in hub are presented in table 3. Supposed when 2z =12 billion, 2d equals zero and when 2z =6 billion,2d equals one. Then calculate the layout scheme 2d of passenger station by linearrelationship. The results are listed in table 10.Table 9 Effect of targets of engineering investment 1d23Costs of passenger trip are shown in table 7. Supposed when 2z =150 billion,3d equals zero and when 2z =80 billion, 3d equals one. Then calculate the layoutscheme 3d of passenger station by linear relationship. The results are listed in table 11.Table 11 Effect of targets of passenger trip 3d4E. Determine the weight of each evaluation indexBy combining all evaluation indexes with a certain nu mber of experts’ suggestions, the weight of each evaluation index is determined: 1w —0.5、2w —0.1、3w —0.3、4w —0.1.F. The optimal layout scheme of passenger stationComprehensive above results, evaluate the total effect of targets of layout scheme of passenger station in Nanning railway terminal. The results are listed in table 13.Table 12 Effect of targets of the other social benefitsd4three-station scheme, the optimal scheme is two-station scheme. That is reconstructing Nanning station and new building Nahuang station.The reconstruction and removal engineering are in large scale. To control the scale of Nanning station effectively, add five intermediate platforms and ten arrival-departure tracks to form fifteen mesas in scale. At the same time, build passenger coach preparing station and motor train-set application station. In Nahuang station, construct five arrival-departure tracks(including main line)、one basic platform、one intermediate platform、eight long-term reservation arrival-departure tracks 、four intermediate platforms and reserve motor train-set storage yard towards the station house.基于多目标规划的铁路枢纽客运站布局优化研究摘要：本文研究铁路枢纽内客运站布局及选址基本原则，客运站布局评价指标既有定量指标也有定性指标，为统一评价指标，本文运用多目标规划的基本思想，引入了评价指标的目标效应值，建立了多目标规划的客运站布局优化模型。