The blocking back model (pseudo-dynamic assignment, pa) fills the gap between merely static procedures, which do not have any temporal reference and cannot determine congestion-related wait times, and dynamic procedures that require long computation times. The blocking back model is not an independent assignment procedure, but it modifies the results of a currently running or a previously run assignment (Fundamentals: Blocking back model).
The blocking back model can be applied together with the following static PrT assignment procedures:
- Incremental assignment
- Equilibrium assignment
- TRIBUT - Equilibrium assignment
- TRIBUT - Equilibrium_Lohse
- Stochastic assignment
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Notes: Please make sure, that the demand remains a realistic value when computing various scenarios with demand being increased step-by-step. Therefore, you should raise the demand by factors like 1.1 or 1.2 gradually. Changes to network data which is relevant to the blocking back model, e.g. capacity, will not automatically adjust the results of a previously calculated blocking back model (corrected volumes, wait times or absolute and relative queue length) accordingly. In this case, you need to re-calculate the blocking back model. An assignment with blocking back model determines the paths with their volumes first. Then, the spill-back impact is calculated which changes the link volumes. For this reason, the volumes of the OD pairs and of the paths resulting from assignment do not comply with the link volumes. Thus, the flow bundle volumes may differ from the link volumes. |
