The quantitative analysis of road network traffic performed through static assignment models yields the transport demand-supply equilibrium under the assumption of within-day stationarity. This implies that the relevant variables of the system (i.e. user flows, travel times, costs) are assumed to be constant over time within the reference period. Although static assignment models satisfactorily reproduce congestion effects on traffic flow and cost patterns, they do not allow to represent the variation over time of the demand flows (for example, around the rush hour) and of the network performances (for example in presence of time varying tolls, lane usage, signal plans, link usage permission). Most importantly, they cannot reproduce some important dynamic phenomena, such as the formation and dispersion of vehicle queues due to the temporary over-saturation of link sections, and the spillback, that is queues propagation towards upstream links. For these use cases, dynamic models are available.
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Note: In the directory C:\Users\Public\Documents\PTV Vision\PTV Visum 2021/Examples, you can find an example of use on this topic. The PrT Assignment DUE example describes two variants (with and without spillback) of the dynamic user equilibrium assignment. |
