lect5_6 - INTRODUCTION TO TRANSPORTATION SYSTEMS Lectures...

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Nigel H.M. Wilson 1.201, Fall 2006 Lecture 5 1 INTRODUCTION TO TRANSPORTATION SYSTEMS Lectures 5/6: Modeling/Equilibrium/Demand
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Nigel H.M. Wilson 1.201, Fall 2006 Lecture 5 2 OUTLINE 1. Conceptual view of TSA 2. Models: different roles and different types 3. Equilibrium 4. Demand Modeling References: Manheim, Fundamentals of Transportation Systems Analysis , Chapter 1 Gomez-Ibañez et al., Essays in Transportation Economics and Policy , Chapter 2
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Nigel H.M. Wilson 1.201, Fall 2006 Lecture 5 3 CONCEPTUAL VIEW OF TSA 3 elements in transport system problems: Transport system, T Activity system, A Flow pattern, F T A F III I II
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Nigel H.M. Wilson 1.201, Fall 2006 Lecture 5 4 CONCEPTUAL VIEW OF TSA 3 types of inter-relationships: Type I: Direct interaction between T and A to produce F The short-run "equlibrium" or outcome Many problems are dynamic rather than static Type II: Feedback from F to A A is continually in flux with some changes resulting from F Type III: Transport system changes as a result of F Transport operator adds service on a heavily-used route New highway link constructed
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Nigel H.M. Wilson 1.201, Fall 2006 Lecture 5 5 MODELS: DIFFERENT ROLES AND DIFFERENT TYPES Models represent real system to predict impacts if specific actions are taken Key elements of a model: Control variables: the decision variables Indirect control variables: these are indirectly affected by decisions Exogenous variables: known a priori , not affected by interactions Relationships between variables Parameters or coefficients
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Nigel H.M. Wilson 1.201, Fall 2006 Lecture 5 6 MODELS: DIFFERENT ROLES AND DIFFERENT TYPES Attributes of a model: Complexity Accuracy Data Requirements Computational Requirements Estimation Requirements
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Nigel H.M. Wilson 1.201, Fall 2006 Lecture 5 7 ROLES FOR MODELS IN TSA Performance models: predicts performance or service equality at different flow levels Demand models: predicts the flows that result at different levels of service quality and price Equilibrium models: predicts F , given T and A , or finds flow which simultaneously satisfies performance and demand relationships Activity shift models: predicts changes in A over time Competitor response models: predicts response by other operators to F and changes in T
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Nigel H.M. Wilson 1.201, Fall 2006 Lecture 5 8 PREDICTION REVISITED Existing T + Proposed Actions Existing Activity System, A Competitor Response Model Equilibrium Model Activity Shift Model Service/ Performance Model Demand Model Impacts
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Nigel H.M. Wilson 1.201, Fall 2006 Lecture 5 9 TYPES OF MODELS Descriptive: typical models for performance and demand simulation models systems of linear or non-linear equations cross-sectional vs time-series Optimization: used in designing some aspects of the transportation system continuous or discrete variables linear or non-linear functions
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Nigel H.M. Wilson 1.201, Fall 2006 Lecture 5 10 TRANSPORT DEMAND Basic premise: transport is a derived demand Classic simple demand function for a single O-D pair with fixed activity system Time Vol V 1 V 0 t 1 t 0
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Nigel H.M. Wilson
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lect5_6 - INTRODUCTION TO TRANSPORTATION SYSTEMS Lectures...

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