The latest release of Aimsun Next (version 8.3, released September 7th 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.
Aimsun Next 8.3 has been developed with a focus on improving the performance of all model runs, enriching the tools for the preparation of the traffic demand, and removing some constraints when running microsimulation with pedestrians.
Quite simply, this is the fastest version yet of Aimsun Next. Performance improvements include:
Supernodes have been modified to extend their functionality:
A new Dynamic OD Departure Time Rescheduling Experiment has been provided. This adjustment performs peak spreading to simulate drivers changing their departure time to achieve the same arrival time as congestion in the road network increases. The adjustment is based on the HADES (Heterogeneous Arrival and Departure Times with Equilibrium Scheduling) algorithm, which was developed by Mott Mac Donald on behalf of the UK Department for Transport. The algorithm estimates a new departure time based on the perceived cost of reaching a destination outside of the previously experienced arrival time window.
If detectors or detector stations are close to the end of the section and cover group of lanes that corresponds to a turn or a group of turns, the adjustment associates the real data to those turns instead of extrapolating to the section, making a better use of the information you provide.
The London Emissions Model (LEM) is a new mesoscopic emissions model developed in collaboration with Transport for London (TfL) in response to observations that average speed models tended to under-predict emissions at low speeds and that variability in vehicle activity meant that predictions based on average link speeds on short links or for short time periods had significant uncertainty. The LEM model approach is to derive the emissions for and individual vehicle using its average speed in a set of micro trips that form its whole journey. A micro trip is defined as a segment of the trip where the speed rises from stationary to > 5 km/h and back to stationary as illustrated below in a typical plot of speed vs time in an urban drive cycle.
The LEM was calibrated in 2017 using measurements taken in London.
The Detailed Node View has been revised to improve visualisation of assigned volume, count, and flow data for a node.
Subpaths are able to filter the outputs they collect to select only those vehicles on a selection of public transport routes.
The Re-Evaluate when Travel Time Is Updated option in the Forced Enroute Assignment action causes vehicles that have already been affected by the enroute action to re-consider their route choice if a DTA paths update occurs while they are on the road section where the traffic action takes place.
For each destination section in a Forced Turn action it is now possible to specify more than one subpath with the proportion of vehicles to follow it.
Now you are not limited to using a 0.6 second timestep when simulating using Legion for Aimsun. Legion for Aimsun will still use a fixed 0.6 second timestep but the microsimulation model hosting the Legion pedestrians can now be configured to use any time step length you like.
The plugin has been updated to work with Legion Spaceworks 6.5.2.
Mesoscopic simulation is now able to use multiple threads in a CPU and hence run faster in large models. The number of threads is specified in the mesoscopic experiment.
In a DUE Result there is an option to disable queue propagation. This has the effect of giving road sections an infinite storage space and prevents queue propagation. This option is intended to be used in a preliminary DUE run aimed at producing an APA file to warm-start a DUE process. If a DUE is run without an input path file, over-saturation on some sections is likely to cause gridlocks that distort the path calculation in later iterations. By disabling queue propagation, this option prevents gridlocks and thus allows a cold-start DUE find reasonable paths to be fed in a DUE run without this option. This option should only be used to prepare an initial set of paths, and not to produce final results.
An Initial State may be saved and used to initialize a hybrid simulation experiment.
In dynamic assignment, the cycle time sets how often path costs are re-computed and a different set of paths is provided to vehicles departing during the following interval. The changes in path costs, and hence the changes in the path choice set, will be higher during the peak periods than during off-peak periods, therefore the cycle time should be shorter during the peak periods than during off-peak periods.
The Profiled Route Choice option allows route choice intervals to be grouped and the path costs evaluated at less frequent intervals when there is less variation in congestion and hence less need to re-compute path costs and vary path choice.
A Detector Station is a defined set of detectors in a single section used to automatically aggregate statistics from them. Data for detector stations can be imported into a Real Data Set and used as if it represented one detector.Detector stations have two main objectives:
A filter in the Geometry Configuration Editor has been implemented to help manage the list of objects which exist, or do not exist in a Geometry Configuration.
Russian has been added to the Aimsun Next Software in addition to the existing Spanish, Portuguese and French translations.
The Lisa+ adaptive signal controller dynamically controls signals based on the actions of vehicles passing over detector loops in the vicinity of the signalized junctions to optimize the traffic flows. Aimsun Next is now able to use the Lisa+ Controller to provide dynamic control of simulated signals using the Adaptive Control Interfaces extension.
The existing SIDRA control plan importer/exporter is now able to export the network geometry to SIDRA. It has also been updated to work with SIDRA Intersection 8.0.
WMS (Web Map Service) is a protocol for serving geo-referenced map images from a server. Aimsun Next is now able to import WMS images into a new graphical layer and display them in the simulation model.
Functions are available to manage public transport routes in response to incidents by making changes to the route either for all vehicles, a proportion of vehicles, or for a specific vehicle following that route. Changes are made using new API functions
Some Traffic Management Actions were not accessible via the API. New functions have been included in Aimsun Next 8.3 to correct this. The new functions are:
The main change in Aimsun 8.3 is the deprecation of all the different scripting classes to do the calculation procedures (dynamic simulations, assignment, adjustment, outputs retrieval, travel demand modelling procedures, etc.).
Those classes and functions have been substituted by a mechanism, called Kernel Actions, for the different calculation procedures (dynamic simulations, assignment, adjustment, travel demand modelling procedures, etc.) to provide a common interface to command their execution.
Aimsun Next version 8.3 uses QT 5.9 in the Mac and Linux versions and QT 5.6 in the Windows version.