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1、谭志加Office#616,华中科技大学管理学院,交通组织运输学,The 4-Step Model,Transportation Planning,Modal choice,train,bus,auto,Transportation Planning,Transportation Planning,Modal Choice,Overview,Methodologies Discrete choice analysis Logit models,Transportation Planning,Mode usage(modal choice,or modal split)analysis is t
2、o estimate the proportion of trip-makers traveling between each pair of origin-destination zones who are likely to use each mode(public transit or auto).Understand the factors that influence individual choices of travel modesEvaluate the impacts of alternative transport policies on modal splitHow to
3、 achieve a balanced use of different travel modes through efficient traffic control and management(e.g.road pricing),Objectives of Modal Choice Analysis,Transportation Planning,Factors Influencing the Choice of Mode,Characteristics of the Trip-makerCar availability and/or ownershipPossession of a dr
4、iving licenseHousehold structureIncomeResidential density,Characteristics of the Journey(Trip)The trip purposeTime of Day when the journey is undertaken,Transportation Planning,Factors Influencing the Choice of Mode,Characteristics of the Transport FacilityQuantitative factors such as:Relative trave
5、l timeRelative monetary costsAvailability and cost of parkingQualitative factors(less easy to measure)such as:Comfort and convenienceReliability and regularity,Transportation Planning,Basic Consideration of Modal Choice,The factors influencing the choice of modes are used as independent variables to
6、 be included in mathematical models of modal choice.The dependent variable being the market share or the percent of travelers that are expected to use each of the available modes.The planner looks at how these characteristics interact to jointly affect the trip makers choice of mode.When the relatio
7、nships have been discovered,the planner can predict how the population of the future will choose from among the modes that will be available.,Transportation Planning,Utility and Disutility Functions,Modal choice has a relationship with the utility.The utility(or disutility)function is typically expr
8、essed as the linear weighted sum of the independent variables or their transformation:,V is the utility derived from a choice defined by the magnitudesof the attributes X that are present in that choice and that areweighted by the model parameters a,parameters can beestimated by linear regression,ba
9、sed on actual choice results.,Transportation Planning,Example of Disutility Functions,A linear utility function:,Where X1=in-vehicle travel time X2=monetary cost X3=cost/income X4=reliability,Continuous vs.Discrete Goods,Bus,Auto,Indifferent curve,Budget curve,Transportation Planning,Discrete Choice
10、 Analysis,Time cost,Monetary cost,Continuous vs.Discrete Goods,Transportation Planning,Discrete Choice Analysis,快递公司,Discrete Choice Framework,Decision-Maker-Individual(person/private/public sector)-Socio-economic characteristics(income,objectives)Alternatives-decision-maker n selects one facing Jn
11、alternatives set Cn=1,2,Jn with Jn alternativesAttributes of alternatives-Travel time,cost,reliability,safety.Decision rules-Dominance,satisfaction,utility etc.,Transportation Planning,Discrete Choice Analysis,A Simple Example,tastes,Transportation Planning,Discrete Choice Analysis,If U(train)U(bus)
12、-train Probability(train)=1If U(train)bus Probability(train)=0,Transportation Planning,Discrete Choice Analysis,A Simple Example,Imperfect information,Transportation Planning,Discrete Choice Analysis,Random Utility Model,Random Utility Model,Decision rule:Utility maximization-Decision maker n select
13、s the alternative i with the highest utility Ui among J alternatives in the choice set C,Systematic utility:function of the observed variables,Random utility,Choice probability,Transportation Planning,Discrete Choice Analysis,Binary choice,Transportation Planning,Discrete Choice Analysis,Random Util
14、ity Model,Binary Logit(Logistic Probability Unit),Transportation Planning,The Logit Model,Transportation Planning,The Logit Model,S-shaped logit curve used to fit the model data in the case of two modes.A share model to divide the persons between the various modes according to each modes relative de
15、sirability for any given trip.Modes are relatively more desirable if they are faster,cheaper,or have other more favorable features than competitive modes.The better a mode is,the more utility it has for the potential traveler.,Transportation Planning,The Logit Model,Different in times,cost,etc.,Prob
16、ability of using mode i,Pi,is given by,Sum corresponding to all competing modes,Utility-measure the degree of satisfaction of the mode Disutility-measure the generalized cost(impedance.),if given disutility functions,Simplest case,bus,auto,Binary Choice(Bus vs.Auto),Transportation Planning,The Logit
17、 Model,Generalized travel cost,I do not care the cost.For any travel cost,I choose one in probability.,I do care the cost very mush.I choose the one with lower cost in probability 1.,more sensitive,Binary Choice(Bus vs.Auto),Transportation Planning,The Logit Model,Bus share(%),Bus more preferable,Li
18、miting cases,What happens as,What happens as,Transportation Planning,The Logit Model,Binary Choice(Bus vs.Auto),How about the general case?,(1)What happens as,(2)What happens as,Transportation Planning,The Logit Model,Assume that there are two alternatives for Hankou and Wuchang,i.e.Car and Train.Ba
19、sed on survey and calibration,the utility function for the two alternatives are given by,1.Applying logit model to determine the number of passengers using Train QTrain and the car volume between Hankou and Wuchang QCar(assume car occupancy is 1,i.e.one passenger par car).,2.Determine the car volume
20、 suppose,due to traffic congestion,the travel time by car will depends on the car volume on the bridges,given by,3.Change the toll charge for car(Toll),so that the car volume is reduced to,Example,Transportation Planning,1.Applying logit model to determine the number of passengers using Train QTrain
21、 and the car volume between Hankou and Wuchang QCar(assume car occupancy is 1,i.e.one passenger par car).,Solution,Transportation Planning,2.Determine the car volume suppose,due to traffic congestion,the travel time by car will depends on the car volume on the bridges,given by,Solution,Transportatio
22、n Planning,3.Change the toll charge for car(Toll),so that the car volume is reduced to,Solution,Transportation Planning,Transportation Planning,Independence of Irrelevant Alternatives Property(IIA):The IIA property holds that for a specific individual,the ratioof the choice probabilities of any two
23、alternatives is entirelyunaffected by the systematic utilities of any other alternativesin the choice set.,The Logit Model,不相关选择项的独立性,Red/Blue Bus Example,Suppose in a corridor,V(car)=V(bus),so,P(car)=P(bus)=1/2Now suppose that the bus company pants half buses into blue color(the remaining half buse
24、s are still in red color).We thus have RED and BLUE buses as two of the available alternatives.Applying the Logit model P(car)=1/3;P(red bus)=1/3;P(blue bus)=1/3So P(bus):1/2 2/3(Impossible in reality),after changing color,Observed result:P(car)=1/2;P(red bus)=1/4;P(blue bus)=1/4some problems?,Trans
25、portation Planning,Nested Logit Model,Hierarchical Choice Structure,Overcome the IIA Problem of Multinomial Logit Alternatives are correlated(e.g.,red bus and blue bus),Transportation Planning,Nested Logit Model,Arunotayanun,K.,2010.Taste heterogeneity and market segmentation in freight shippers mod
26、e choice behaviour.Transportation Research Part E(in press).,Level of service for freight modal choice:Monetary costTime costReliabilityFlexibilityQualityCargo type and value,Transportation Planning,The Application of Discrete Choice Analysis,ExampleSuppose the dis-utility of the customers demanding
27、 the package delivery service between a specific OD pair is captured using service fare and time costwhere parameter is called value-of-time and follows the following cumulative distribution,For a certain commodity(e.g.,weight below 100g),the total demand is exogenously given,Q.,Transportation Plann
28、ing,The Application of Logit Model,Depicting the suppliers in the market,Transportation Planning,快递公司,The Application of Logit Model,Discussions(1)Which supplier will survive in this market?Why?(2)How does the suppliers act to attract more demand?(3)How to calculate the market share for a certain su
29、pplier?(4)How to capture individual customers perceived error?,Transportation Planning,The Application of Logit Model,Service fare,Service time,(1)Which supplier will survive in this market?Why?,Transportation Planning,The Application of Logit Model,(2)How does the suppliers act to attract more dema
30、nd?,Service fare,Service time,Transportation Planning,The Application of Logit Model,Service fare,Service time,(3)How to calculate the market share for a certain supplier?,Transportation Planning,The Application of Logit Model,Service fare,Service time,(4)How to capture individual customers perceive
31、d error?,Mixed logit model,Transportation Planning,The Application of Logit Model,Piyush,T.,Hidekazu,I.,Masayuki,D.,2003,Shippers port and carrier selection behaviour in China:a discrete choice analysis.Maritime Economics&Logistics,Vol.5,pp:23-39.,Transportation Planning,The Application of Logit Mod
32、el,Transportation Planning,The Application of Logit Model,Problem,Methodology,Standard multinomial logit Model,Port characteristics:ship calls,total TEU,numbers of berths,cranes,offered routesShipping line characteristics:scale(TEU,fleet size)Shipper characteristics:distance,trade type,Transportatio
33、n Planning,The Application of Logit Model,Findings/Contributions,Significance analysis:the significant variables of port are distance,number of berths,TEU.The significant variables of carriers is fleet size.Elasticity Estimation(to capture market shares):,Transportation Planning,The Application of L
34、ogit Model,Verma,R.,Pullman,M.,1998.An analysis of the supplier selection process.OMEGA int.J.Mgmt.Sci,Vol.26(6),pp:739-750.Verma,R.,Kimes,S.and Dixon,M.“New Applications of Customer Choice Modeling in the Hospitality and Related Service Industries”,Cornell Hospitality Quarterly,forthcoming,2010.,Transportation Planning,The Application of Logit Model,Hints:Making choice from discrete alternative set(vendor,supplier choice process;carrier choice;route assignment),
