What is Q-Traf ?

Q-traf is a trip-based macroscopic model which transforms OD trip matrices into traffics flows, by calculating the best route for each vehicle. Traffic assignment is the last step of travel demand/land-use/transportation modeling.

Why Q-Traf ?

There are already a lot of traffic or trips programs.

The points of Q-Traf are :

• free to use, there is no commercial purpose. All files can be read, created and manipulated with free and open-source (FOSS) softwares, like QGis and LibreOffice (but other GIS can be used)
• simple. As it could be
• no weird file formats : all files are *.txt (or *.csv) or shape files (*.shp)
• portable. No installation required. There is only one .exe file
• light. Only 1 Mo

• All the graphic visualization can be done with a GIS (like QGis)

A brief history

Q-traf has been developed through the years, beginning in 2014 with a simple Dijkstra algorithm and delay(flow) functions.

Then QGis has been used for all the graphic visualization and network building.

The simple speed(flow) functions have been replaced with two-phase traffic modelling.

Now Q-Traf can handle multiple OD matrices of multiple types of vehicles. As for the graphical results, they are only limited by what a Gis can do.

Performance and limitations

Q-Traf runs on Windows 10 and 11.

It can handle up to :

• 30 000 links
• 2 000 zones
• 4 categories of road vehicles (car, truck, bus, pedestrian) and 5 sub-types (car, truck)
• Park & Ride (car-bus trip)
• 20 scenarios (sets of networks + matrices, for comparison)
• LHD and RHD
• Day and hour analysis
• provide traffic flow, density, per vehicle type and PCU (Passenger Car Unit), zone analysis

(computing 20 000 links and 2 000 zones required 2 Go of RAM)

Method and principles

The basis of the program are :

• User equilibrium
• link-delay functions
• generalised travel cost (on delay and distance)

How to use the examples

To use Q-Traf with the provided examples, you need to download :

• One or several examples. Each example contains the program Q-Traf and all the folders and files needed. All the files are text files (“.csv” files)
• The notice

To see the results of a trips assignation of an example, you need to :

• (download and install QGis, ArcGis, or another GIS)
• Open a QGis project : The file *.qgz provided in the QGis folder, or create a new one and choose the correct SCR (indicated in the root folder )
• In the GIS, import the .csv files from the folder results (/_out_results_wkt) : Example/_out_results_wkt/troncons or links_xxx/”….uvp.csv” or “….TV.csv”

To run a simulation and calculate a new traffic assignment, you need to :

• Run Q-Traf.exe (in the root folder of each example provided)
• Once the execution is finished, close the window
• The new results are then written in the folder “_out_results_wkt”
• Open the results in a GIS (see above)

Downloads

The current version is Q-Traf 778

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