Capacity-constrained Traffic Assignment in Network with Residual Queues and Implementation in EMME/2

1. Capacity-constrained Traffic Assignment in Network with Residual Queues and Implementation in EMME/2 Yanping ZhangBucher, Willis & Ratliff Corp. 7920 Ward Pkwy, Kansas City, MO 64114Tel.: 816-363-2696, Email: yzhang@bwrcorp.com16th International EMME/2 User’s Group ConferenceAlbuquerque, New Mexico, Mar. 18-20, 2002

2. Network with Residual Queues • Residual Queues - Overcapacity flow • Residual queue delay • Link outflow <= Link exit capacity • Unbalanced O-D flow • Spill-back queues on upstream link

3. Basic Assumptions for Assignment • Assignment for single time period (e.g. peak hour period); • Fixed O-D demands; • Fixed exit capacity for each link; • Vehicles in the residual queue, will follow the chosen route to reach destinations in the next period; • Link cost consists of travel delay cost and the residual queue delay cost; • Drivers always choose thre shortest routes • No spill back effect on travel times in upstream links.

4. Simple Example

5. Comparison of Assignment Results

6. Assignment Model Formulation

7. User Equilibrium Assignment in Network with Queues

8. Solution Method • Adding shadow links and modifying cost function • Shadow links (only for carrying queues)

9. Path Operator in EMME/2 • Cut-off path operator (splitting the queue-delay path flow)

10. Equivalent Model in the Modified Network

11. Approximation of Link Cost Function

12. Solution Algorithm

13. Solution Algorithm

14. Example

15. Conclusion • Model for assignment in network with Queues; • Solution method with modified network; • No consideration of queue spill-back • Extension to Multiple period Assignment.