交通规划-交通模式分割.ppt

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) analysi

2、s is to 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 modes Evaluate the impacts of alternative transport policies on modal sp

3、lit How to 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-maker Car availability and/or ownership Poss

4、ession of a driving license Household structure Income Residential density,Characteristics of the Journey (Trip) The trip purpose Time of Day when the journey is undertaken,Transportation Planning,Factors Influencing the Choice of Mode,Characteristics of the Transport Facility Quantitative factors s

5、uch as: Relative travel time Relative monetary costs Availability and cost of parking Qualitative factors (less easy to measure) such as: Comfort and convenience Reliability and regularity,Transportation Planning,Basic Consideration of Modal Choice,The factors influencing the choice of modes are use

6、d as independent variables to 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

7、choice of mode. When the relationships 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 di

8、sutility) function is typically expressed as the linear weighted sum of the independent variables or their transformation:,V is the utility derived from a choice defined by the magnitudes of the attributes X that are present in that choice and that are weighted by the model parameters a, parameters

9、can be estimated by linear regression, based 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,Bu

10、dget curve,Transportation Planning,Discrete Choice 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, objecti

11、ves) Alternatives -decision-maker n selects one facing Jn alternatives set Cn=1,2,Jn with Jn alternatives Attributes of alternatives -Travel time, cost, reliability, safety. Decision rules -Dominance, satisfaction, utility etc.,Transportation Planning,Discrete Choice Analysis,A Simple Example,tastes

12、,Transportation Planning,Discrete Choice Analysis,If U(train)U(bus)- train Probability(train)=1 If 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 Ut

13、ility Model,Decision rule: Utility maximization -Decision maker n selects 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,B

14、inary choice,Transportation Planning,Discrete Choice Analysis,Random Utility 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 divid

15、e the persons between the various modes according to each modes relative desirability 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 tra

16、veler.,Transportation Planning,The Logit Model,Different in times, cost, etc.,Probability 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 functi

17、ons,Simplest case,bus,auto,Binary Choice (Bus vs. Auto),Transportation Planning,The Logit 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 Ch

18、oice (Bus vs. Auto),Transportation Planning,The Logit Model,Bus share (%),Bus more preferable,Limiting 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 Plannin

19、g,The Logit Model,Assume that there are two alternatives for Hankou and Wuchang, i.e. Car and Train. Based 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

20、 Hankou and Wuchang QCar (assume car occupancy is 1, i.e. one passenger par car).,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,3. Change the toll charge for car (Toll), so that the car volume is reduced

21、 to,Example,Transportation Planning,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).,Solution,Transportation Planning,2. Determine the car volume suppose, due t

22、o traffic congestion, the travel time by car will depends on the car volume on the bridges, given by,Solution,Transportation 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 Alt

23、ernatives Property (IIA): The IIA property holds that for a specific individual, the ratio of the choice probabilities of any two alternatives is entirely unaffected by the systematic utilities of any other alternatives in the choice set.,The Logit Model,不相关选择项的独立性,Red/Blue Bus Example,Suppose in a

24、corridor, V(car) = V(bus), so, P(car) = P(bus) =1/2 Now suppose that the bus company pants half buses into blue color (the remaining half buses 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 b

25、us)=1/3 So 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)=1/4 some problems?,Transportation Planning,Nested Logit Model,Hierarchical Choice Structure,Overcome the IIA Problem of Multinomial Logit Alternatives are correlated (e.g.,

26、 red bus and blue bus),Transportation Planning,Nested Logit Model,Arunotayanun, K., 2010. Taste heterogeneity and market segmentation in freight shippers mode choice behaviour. Transportation Research Part E (in press).,Level of service for freight modal choice: Monetary cost Time cost Reliability F

27、lexibility Quality Cargo type and value,Transportation Planning,The Application of Discrete Choice Analysis,Example Suppose the dis-utility of the customers demanding the package delivery service between a specific OD pair is captured using service fare and time cost where parameter is called value-

28、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 Planning,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 at