The Aimsun Next Environment

Aimsun Next provides an extensible environment that offers all the tools that an analyst requires to support a transport modeling project: importing and editing a transport network; estimating and refining the transport demand; simulating transport movement in static macroscopic assignments or in dynamic mesoscopic, microscopic or hybrid simulation with route paths derived by simple "All or Nothing" methods to complex Dynamic User Equilibrium algorithms. Aimsun Next also provides outputs ranging from 3D animation to sophisticated transport analysis and contains tools to assist in managing a project with a base model and multiple, multi-faceted option tests. All functions are contained in one application operating on a single project document.

An Aimsun Project

A typical workflow for an Aimsun project might include:

• Create a new project with a template and setting up the basic vehicle and road types, described in the New Project Section.
• Import a transport network from CAD, GIS or from other transport models. The Importers and Exporters Section describes how to import as a graphical background or as a pre-prepared transport network from multiple sources.
• Edit the network to refine it by shaping road sections, setting up turns at junctions, creating traffic signals and transit networks and adding 2D and 3D visualization objects. The Network Editing Section describes how to edit the traffic network while the Signal Control Section, the Transit Section and the Annotation Section describe how to add more features to the network.
• Edit the vehicle and user types to segment traffic demand . The demand might be a simple "Traffic State" based on observed counts only or it might be a "Traffic Demand" based on an OD demand matrix with a centroid configuration to represent a zoning scheme for the demand in the model. This is described in the Demand Section.
• Run a dynamic simulation using the microscopic simulator, the mesoscopic simulator the hybrid meso-micro simulator or the hybrid macro-meso simulator. Alternately the model can be used to assign traffic using the macroscopic module for a static traffic assignment.
• If needed, pedestrians can be included in a microsimulation model with the embedded pedestrian simulator.
• Dynamic traffic control can be simulated with adaptive signal control to include signal control systems such as SCATS or Yunex UTC (with SCOOT). ITS systems can be simulated with the traffic management tool set.
• Travel demand can be modeled to include trip generation, and trip distribution, and modal split. The OD matrices output by this process can be refined using the OD matrix tools and the matrix adjustment scenario.
• Outputs can be in the form of thematic maps, as animated views. Analytical outputs include graphs, data comparisons between model scenarios or with real data or might use specialized tools such as link analysis or isochrones, documented in the Analysis Section. They are also stored in the outputs database.

Aimsun Next includes management tools to manage different scenarios in a model. For example a typical project might have a base model and a number of road design options to test, the project might then require that options are tested in different traffic demand scenarios and with different signal control systems. Aimsun Next also provides tools to allow multiple modelers to collaborate on a single project.

Extendibility

Aimsun Next can be extended by users using programming tools at five levels.

• Aimsun Next scripting: Scripting is designed to automate operations that would otherwise be done manually with the GUI. Scripts can be used to import model data or to provide custom tools to automate editing.

• Aimsun Next API: Using the Application Programming Interface, it is possible to program operations that act during the microsimulation by changing signal control timings,ITS management, or vehicle parameters. The API is typically used in simulating advanced ITS or customized signals.

• Aimsun Next microSDK: The Microsimulator Software Development Kit is used to develop new microscopic simulation models (car following, lane changing, etc.) replacing those included in the Aimsun Next Microsimulator.

• Aimsun Next External Agent Interface: It gives a simple method of connecting a driving simulator or CAV controller to an Aimsun Next microsimulation.

• Aimsun Next V2X SDK: Designed to provide an extensible platform to include vehicle-to-vehicle and vehicle-to-infrastructure communications using standard CAV protocols or custom-developed, role-specific protocols in an Aimsun Next microsimulation.

This manual covers all aspects of modeling with Aimsun Next. It contains sections which describe editing a model, running a model, managing a model, and adding more complex features to a model. It finishes with a section reviewing the theoretical foundations of Aimsun Next and the algorithms it contains.