The latest release of Aimsun Next (version 8.2.3, released March 2018) includes significant improvements to Aimsun Next traffic modeling software, both at the modeling and platform levels. This is a quick guide to the main highlights, followed by a breakdown of all enhancements and new features – you can also read this in the Aimsun Next software itself – just look up the New Features Guide after installation.
This procedure fits a multi-class, time-sliced demand to a real data set of traffic counts for multiple time intervals within the simulation period, be it a microscopic, mesoscopic or hybrid simulation.
Public Transport Assignment now supports a cost component that depends on: the load of the line (crowding); the calculation of an effective line frequency that reflects failure-to-board situations (congestion); flat and zone-based fare cost (in addition to fixed boarding fare cost and distance-based fare cost).
There are more DUE assignment options than ever: route a portion of the vehicles along pre-defined OD Routes; enjoy greater control over the choice set of alternative paths by providing an initial set of paths coded as OD Routes or read from a previously generated Path Assignment File; achieve convergence faster thanks to a new gradient-based assignment algorithm and the ability to discard paths that are not used much.
We’ve merged previous path assignment and path statistics into one path analysis tab, plus we’ve added all real vehicles paths. You can also visualise the paths of vehicles affected by a traffic management or vehicles that miss a turn.
Set a target Relative Gap by OD pair as stopping criterion for a Dynamic User Equilibrium assignment, and output the Relative Gap by OD pair at the end of both a Dynamic User Equilibrium and a Stochastic Route Choice assignment. You can see the sections that are more stable or unstable in terms of counts and travel times too.
We’ve improved car-following in congested conditions by using a modified Gipps model to achieve more accurate simulated speeds.
The previously combined Trip Distribution and Modal Split scenario has been separated into a Distribution Scenario and a Modal Split Scenario with the Distribution trip matrices stored in the project folder for input to the Modal Split process.
The Public Transport Assignment has been converted into an Iterative Equilibrium process in order to take into account crowding in the cost functions.
The Effective Frequency Model models the failure-to-board situation that can occur in a period of heavy congestion. To achieve this, the Effective Frequency Model updates the Public Transport Line frequency for a target stop to increase the waiting time faced by the boarding passengers when the residual capacity of the Public Transport Line is insufficient.
The Flat Fare structure uses a single entrance fare that will be added at the first use of a Public Transport Vehicle and allows the passenger to subsequently transfer within the Public Transport Network with no additional fare cost.
The PT Zone Fare structure adds an additional fare cost for travelling between different zones or within a single zone.
The Public Transport OD adjustment procedure now uses the equilibrium PT assignment engine to perform the network loading.
The Static Assignment Scenario and the Static OD Adjustment Scenario now take a Control Plan as input. The average cycle times and phases of each turn are exposed to be used in Turn Penalty Functions. In the Aimsun Next template, the Turn Penalty Functions are adapted to take into account the Control Plan included n the scenario.
An incremental DUE loads the demand in stages in the early iterations which helps prevent gridlocks as the route paths evolve. This enables the process to reach convergence faster.
Pre-defined OD Routes may be included in the route choice. In a SRC they are added in the set of path alternatives that will be used in the route choice function and in the DUE they are added in the path set that will be used either in the MSA or Gradient-based methods.
Several options have been added to the DUE assignment. The Traffic Assignment tab of the Experiment has been redesigned to provide access to the new functionality, simplify the configuration of the parameters, and offer a more consistent UI between DUE and SRC.
The new assignment method calculates the fraction of traffic that is rerouted on the shortest path based on the difference between the path cost and the shortest path cost, and uses this to reach convergence faster.
A path used by a fraction of vehicles below a user-defined threshold will be discarded. This opens a space in the paths list for a new and more efficient path to appear and to be added to the set of alternative paths.
A fraction of the vehicles may be designated to follow pre-defined OD Routes instead of paths calculated by the DUE.
For those vehicles not following OD Routes, the DUE can be made to use the alternative paths provided as input in a Path Assignment file or as OD Routes, and their utilisation updated without adding new paths.
A Relative Gap Matrix can be defined as the stopping criterion; when an OD pair reaches its specific target RGap, its alternative paths and path proportions are no longer updated.
In a DUE assignment, convergence may be analysed by section to identify those that are more stable or unstable in terms of counts and travel times.
Statistics from vehicles that have completed any subpath are now available in the Database (table SUBPATH_VEHICLES).
Statistics for a Subpath can be calculated using only the vehicles that use a specified turn to enter and/or exit the Subpath.
The relative gap is now also calculated in a one shot simulation and can be accessed in the time series of the Replication.
The Relative Gap can be output by OD Pair for both DUE and SRC Experiments and stored as an OD Matrix.
The Path Assignment and Path Statistics dialog tabs have been merged into one Path Analysis tab. Now the theoretical path percentages calculated by the assignment and the actual path percentages resulting in the simulation are presented together. Link analysis can be performed considering either of these percentages. Paths loaded from a Path Assignment Result and or OD Routes are visible during the simulation and so are paths of vehicles affected by a traffic management action or vehicles that missed a turn.
Record the animation of a microscopic or mesoscopic simulation and then replay it for easier analysis of events that occurred during the simulation.
There is a modified Gipps model which uses a vehicle aggression parameter to achieve simulated speeds under congested conditions in highways closer to the speeds observed.
The two-lane car-following has been extended to support the case in which adjacent lanes in the same direction are coded as separate sections. Two adjacent subpaths can be selected and the two-lane car-following model will be applied in their sections.
The active signal group can be designated “flash in red” where vehicles behave as in front of a stop sign, “flash in yellow” where vehicles behave as in front of a yield sign, or “flash in green” where vehicles behave as in front of a solid green.
The stop line, located by default at the end of the section, can now be moved back. It can also have a different position on each lane.
A Section may now be coded with lanes of different widths.
Vehicles can be forced to slow as they pass an incident in a section to simulate the increased hazard of passing the incident.
The Attractiveness parameter was set for a section in the Section Editor. It is now set for each turn in the Turn Editor mirroring the internal logic of Aimsun Next where it is applied for each “link”, (the section and turn combined) and allowing more control over the costs in the path costs calculations.
Trajectories for Pedestrians can now be output giving global or detailed trajectories.
A mesoscopic simulation can be started with an Initial State.
As mentioned in the highlights section, a mesoscopic simulation or a microsimulation may be recorded and replayed forwards and backwards to analyse events in the simulation using the Record option.
A new action is available that applies an enroute (a new path selection with updated costs) at a given location of the network.
There is now a GUI for the APA Fixer which takes a Path Assignment file and adjusts it so it can be used in a network with modified geometry.
The user interface to define a new project has been modified to configure the main settings in a more user-friendly way.
The User Manual and tutorials are now available also as ePub.
An interface with SCATS ITS Dataport for users with access to the Adaptive Control Interfaces license has been included.
For dynamic simulations that receive the control information from SCATS controllers, it is now possible to generate files for each controller with the information received.
It is now possible to simulate SCATS controllers without connecting to SCATSim. This uses log files with the signal group information instead. The log files are derived from a previous Aimsun Next simulation or from historical SCATS ITS Dataport files.
An Interface to export flows from Aimsun Next to “SIDRA Intersection” and to import the resulting Control Plan from “SIDRA Intersection” has been included.
A General Transit Feed Specification (GTFS) importer has been included. GTFS, also known as GTFS static, defines a common format for public transport schedules and their associated geographic information.
OpenStreetMap decoration and additional geometry may be imported using the extended OSM Importer into an existing Aimsun Next model.
Aimsun Next can read and write matrices using the OMX file format.
The Versit extension for the microscopic simulator generates a file that will be read by Versit+.
Versit is used to predict representative emission factors and energy use factors for vehicle fleets where the emission factors are differentiated for various vehicle types and traffic situations, and take into account real-world driving conditions.
The interface to import a Vissim model is now compatible with Vissim *.inpx files up to version 8.0.
A file is output from a dynamic simulation to give the headways between vehicles as they cross a signalised junction stopline. This file is intended to be used to calculate Saturation Flows at junctions.
Now Aimsun Next supports the use of Python 3rd-party libraries by loading the paths to the modules.
Aimsun Next 8.2 uses QT 5.6.