Capacity-constrained Traffic Assignment in
Network with Residual Queues and
Implementation in EMME/2
Yanping Zhang
Bucher, Willis & Ratliff Corp.
7920 Ward Pkwy, Kansas City, MO 64114
Tel.: 816-363-2696, Email: [email protected]
16th International EMME/2 User’s Group Conference
Albuquerque, New Mexico, Mar. 18-20, 2002
Network with Residual Queues
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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
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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.
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
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Model for assignment in network with Queues;
Solution method with modified network;
No consideration of queue spill-back
Extension to Multiple period Assignment.