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Running a Simulation

In Aimsun Next, a scenario is based in the method of running the model; as a macroscopic assignment model, as a four stage planning model, or as a micro, meso, or hybrid simulation. Once the method of running the model is selected, the base network and demand configuration is described for the scenario and different experiments are created which contain the options to be tested.

This topic presents the ability of the Aimsun next to create scenarios and experiments with different options of network topology, transport demand, simulation method, and sets of calibration variables to provide an efficient method of generating the multiple model variants of a single traffic network and supporting the model management task.

The various Scenarios, Experiment, Results and Replications are:

  • Dynamic Scenarios and Experiments: Each Dynamic Scenario can include several Vehicle based simulators Experiments such as Micro, Meso, hybrid Meso-Micro or Macro-Meso and two different modes of Dynamic Traffic Assignment: Stochastic Route Choice (SRC) and Dynamic User Equilibrium (DUE).

  • Static Assignment Scenarios: In a Static Assignment Model, trips are assigned to the network using a choice of deterministic algorithms or a stochastic method.

  • Travel Demand Scenarios: A project which includes Travel Demand modeling uses a Four-Step Process which links trip generation with travel mode choice and assignment to the transport network. A Travel Demand model can include Generation/Attraction experiments, Distribution experiments, and Transit Assignment experiments. As with the static and dynamic assignment scenarios, different scenarios with different land use patterns and traveler response assumptions can be run using from a single document incorporating different road network changes as required.

Aimsun Next holds all options in one document and only brings them together as a model for each of the variants modeled by an experiment within a scenario. Multiple scenarios can be created in one document and as there is only one copy of each model component rather than multiple copies spread around multiple different models, the task of ensuring all model variants are consistent is greatly reduced. Furthermore, the method of simulation, (micro, meso, or hybrid), or whether this is to be a macro assignment is determined by the scenario and the model generated from the same data in the document.

If a scenario is used to describe the conditions placed on the transport network, an experiment is then used to describe the actions the transport planners might adopt in mitigation. For example, one scenario might be based on the premise that residential or commercial development has been planned and the experiments in that scenario look at the effect of options to cope with the increased demand. Another scenario in the same network might keep the network and demand constant and contain a set of experiments which look at the effect of signal and ITS control options on the existing congestion.

Well planned use of scenarios and experiments has the ability to save time in the transport modeling process and reduce the amount of error prone data transfers between modeling systems.

Also you will find a Command Line Options guide to launch an Aimsun Next simulation by using a command with the graphical user interface or in a console window with no UI.