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What is Q-Traf ?

Q-Traf is a trip-based macroscopic program which calculates and draws traffic flows, based on OD trip matrices, by calculating the best route for each vehicle (“assignment”). Traffic assignment is the last step of travel demand/land-use/transportation modeling.

Q-Traf can handle large scale network, with more than 30 000 links, 2 000 zones, tens of matrices and 10 different categories of vehicle.

Apart from the demand (trips matrices), a large scale network can be modelling in a day or less if a GIS road layer is available.

Why Q-Traf ?

There are already a lot of traffic or trips programs.

The points of Q-Traf are :

• All the graphical modelling and data visualization are done with a GIS (like QGis)

• 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), and WKT (Well Known Text) and shape files (*.shp)
• portable. No installation required. There is only one “.exe” file
• light. Only 1 Mo

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)

Downloads

The current version is : Q-Traf 780d

Installation

There is no software installation needed. Just double-click on Q-Traf.exe (in the root folder of each example provided).

But the program in itself is not enough ; you need all the necessary folders and files of the input data. They are all provided in the examples to download. The list and details of the needed data, and their structures, are described in the “Users manual”.

How to use the examples

Q-Traf needs some data files and folders. 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 a provided example, you need to :

• have a GIS (as QGis, ArcGis, or another)
• Open a QGis project : With 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 / launch 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)

Users Manual

Changelogs

Version 780

Modification of the structure of the file “2_veh_sub_parent_types_and_link_autorization.csv”. Old files don’t work anymore with Q-Traf version 780.

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