Lecture 2.pdf

Transportation supply and demand Lecture 2 Prediction of flows Flow prediction in TAF system Supply and demand function existence of equilibrium Transportation - demand Transportation - supply Equilibrium Service and demand functions Specifying T establishes...

Transportation supply and demand Lecture 2 Prediction of flows Flow prediction in TAF system Supply and demand function existence of equilibrium Transportation - demand Transportation - supply Equilibrium Service and demand functions Specifying T establishes a Service function, J S = J(T, V) Specifying A establishes a Demand function, D V = D(A, S) S => Level of service (TT, C, etc) V => Vol of travellers (Pax, Cars, etc) Flow Pattern, F consists of equilibrium volume, V0 using the system and level of service, S0 0 0 F = (V ,S ) Equilibrium Service and demand curves Existence of simple equilibrium Equilibrium between supply and demand Transportation intervention - Improvement in service If transportation system To is improved to T1 e.g. by adding traffic lanes. The service attribute S will also change and there will be equilibrium shift. Introduction of a new facility Example Service function Demand Function Flow pattern and Equilibrium Solution Determine F = (V, S) algebraically. Determine F = (V, S) using the graphical method Solving the problem gives V = 2,000 V/hr and t = 30 minutes. [ F  (2000, 30] Consider a new service function t = 10 + 0.005V and solve the problem for the same Demand. Activity/system shifts (relations 2 and 3) These are shifts due to changes in both T and A. (T1, A1) [F1 = (V1, S1)]  A11 Effect of activity-system changes Introduction of a new road – 10 yrs Prediction – Broader view Resource requirements Basic prediction models Service models i.e. S = J(T, V) Demand models i.e. V = D(A, S) Equilibrium models (Short term equilibration) Resource models – Resource requirements Activity shift models - long term changes as a consequence of short term flow patterns Basic prediction models Core of TSA Establishing relationship between TAF Project changes in Activity Propose changes in Transportation Predict resulting Flows And the associated Impact Google earth flow projection NexTA Model flow projection TransDNA flow projection TransCAD assignment model Overview of travel demand modeling