Travel Demand Forecasting Traffic Assignment CE 331 Transportation
- Slides: 15
Travel Demand Forecasting: Traffic Assignment CE 331 Transportation Engineering
Overall Procedure Land Use and Socioeconomic Projections Trip Generation Trip Distribution Modal Split Traffic Assignment Direct User Impacts Transportation System Specifications
Traffic Assignment ¢ What route to choose? l l ¢ Input l l l ¢ Mostly for auto mode Intermodal network OD matrix by mode Roadway network (for auto) and/or transit network Characteristics (travel time, cost, …) of each route connecting an OD pair Output l Vehicular flow on each link of the network
Assignment Techniques ¢ Basic Assumption l ¢ Travelers always choose the least cost route connecting the OD All or nothing assignment Assign all trips/vehicles to the route with minimum cost l Assume travel time does not change with volume l ¢ Equilibrium assignment
All or Nothing Assignment 10 min 600 veh 600 O D 12 min 0 veh If there are 600 vehicles traveling between O and D, all of them will be assigned to the shortest route (with 10 min travel time).
Problems of “All or Nothing” Assignment Ignore capacity constraint ¢ Ignore the fact that travel time is related to flow level ¢
Highway Performance Function ¢ Flow-dependent travel time l l Free flow travel time (tf) Typical form: a. k. a. BPR function
Equilibrium Assignment ¢ Basic Assumptions Travelers know the exact cost of choosing each route l Travelers always choose the routes that minimize their own travel cost l
User Equilibrium Model travelers’ route choice behavior ¢ Equilibrium condition: ¢ l Between an OD pair, • All used routes will have the same travel time; • All unused routes will have longer travel time(s).
Example 1 t 1 = 6 + 4 x 1 (thousand vehs) 4500 O D t 2 = 4 + x 22 x 2 (thousand vehs) At equilibrium, let t 1 = t 2 6 + 4 x 1 = 4 + x 22 x 1 + x 2 = 4. 5 x 1 = 1. 6 x 2 = 2. 9
Population, Household by TAZ – Woodford County
Estimated Speed
Congestion Level (V/C ratio) Estimation
- Travel demand forecasting
- Air travel demand forecasting
- What is demand estimation in managerial economics
- Intelligent traffic solutions
- Inbound traffic vs outbound traffic
- Transportation and assignment problems
- Hungarian algorithm worksheet
- Objectives of assignment model
- Chapter 10 driving in rural areas
- Chapter 10 driving in rural areas
- Forecasting and demand measurement in marketing
- Demand forecasting in operations management
- Statistical methods of demand forecasting
- Simultaneous equation method in demand forecasting
- Objectives of hrp
- Collaborative demand planning