capacity-constrained traffic assignment in network with residual queues and implementation in emme/2...

Capacity-constrained Traffic Assignment in Network with Residual Queues and

Implementation in EMME/2Yanping Zhang

Bucher, Willis & Ratliff Corp. 7920 Ward Pkwy, Kansas City, MO 64114

Tel.: 816-363-2696, Email: yzhang@bwrcorp.comTel.: 816-363-2696, Email: yzhang@bwrcorp.com

16th International EMME/2 User’s Group Conference16th International EMME/2 User’s Group ConferenceAlbuquerque, New Mexico, Mar. 18-20, 2002Albuquerque, New Mexico, Mar. 18-20, 2002

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

Basic Assumptions for Assignment

1) Assignment for single time period (e.g. peak hour period);

2) Fixed O-D demands; 3) Fixed exit capacity for each link;4) Vehicles in the residual queue, will follow the chosen

route to reach destinations in the next period;5) Link cost consists of travel delay cost and the residual

queue delay cost;6) Drivers always choose thre shortest routes7) No spill back effect on travel times in upstream links.

Simple Example

Comparison of Assignment Results

Assignment Model Formulation

User Equilibrium Assignment in Network with Queues

Solution Method

• Adding shadow links and modifying cost function

• Shadow links (only for carrying queues)

Path Operator in EMME/2

• Cut-off path operator (splitting the queue-delay path flow)

Equivalent Model in the Modified Network

Approximation of Link Cost Function

Solution Algorithm

Solution Algorithm

Example

Conclusion

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