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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: [email protected].: 816-363-2696, Email: [email protected]
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
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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
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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.
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Simple Example
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Comparison of Assignment Results
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Assignment Model Formulation
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User Equilibrium Assignment in Network with Queues
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Solution Method
• Adding shadow links and modifying cost function
• Shadow links (only for carrying queues)
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Path Operator in EMME/2
• Cut-off path operator (splitting the queue-delay path flow)
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Equivalent Model in the Modified Network
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Approximation of Link Cost Function
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Solution Algorithm
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Solution Algorithm
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Example
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Conclusion
• Model for assignment in network with Queues;• Solution method with modified network;• No consideration of queue spill-back • Extension to Multiple period Assignment.