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Department of Transport and Main Roads

Vehicle Path

Vehicle Path (VPath) calculates the swept path of vehicles which follow a predefined steering path. Vehicle swept paths are used in road design to check that there is sufficient room for turning vehicles to operate safely on the road network and to avoid causing damage to roadside furniture. Swept path templates are also used by vehicle designers to check that vehicles will meet the swept path performance standards set by vehicle licencing authorities.

The primary intention behind VPath is to enable the design of Queensland Transport and Main Roads intersections with reference to vehicles defined in Austroads Design Vehicles and Turning Path Templates (AP-G34-13). Extensive standard and custom vehicle lists are provided.

VPath 4 modernises the underlying code and enhances the user interface.

VPath 4 can operate in 3 modes:

  1. Standalone with no additional software required.
    1. Paths can be generated using:
      1. Horizontal Cubic Splines
      2. IP Curves
      3. Angle of Turn
    2. Export is via DXF
      1. All AutoCAD and 12d Model source path types can be exported to DXF.
      2. Hatch export has proved troublesome due to AutoCAD object handle issues. Envelope hatching is not supported.

  2. Interoperating with a running AutoCAD session with an open DWG file
    1. AutoCAD POLYLINE or LWPOLYLINE objects can be used as reference paths.
    2. AutoCAD LINE objects can be used to generate templates in specific locations.
    3. Export is direct to the current, open AutoCAD DWG file.
      1. All standalone and 12d Model sourced path types can be exported to AutoCAD.
      2. Hatch export has proven troublesome due to some version specific behaviours. Envelope hatching is not supported.
    4. AutoCAD LT is not supported. 
      1. This is due to LT not supporting “add-on apps” or tools employing Autodesk’s Application Programming Interface (API).
      2. Export via DXF.
    5. The “COM Interop” technology used is not perfect. See Known Issues below.

  3. Interoperating with 12d Model after launching from 12 Model via a supplied macro.
    1. Path 4 no longer relies on the 12d Solutions supplied and maintained macro.
    2. Inclusion of a 12d menu item is via “Tools->Options->12d user menu” which enables editing of your usermenu.4d file.
    3. Export is direct to the current 12d Model project.
      1. All standalone and AutoCAD sourced path types can be exported to 12d Model.
      2. Once VPath is launched from 12d, it is possible to export to all three export targets.
      3. Envelope hatching is supported when envelopes are requested.
    4. Interaction with 12d is not perfect. See Known Issues below.

All paths for the current “session” of VPath can be saved to a “session” file with the extension “.vpsession”.  

  • This file can be exchanged with other VPath 4 users.  
  • All custom vehicle definitions are carried with this file.
    • These are appended to the recipients custom vehicle file when the session file is loaded.
  • The consumer of the session file does not need AutoCAD or 12d Model to export to DXF.

Known issues

AutoCAD “COM Interop”

Based on Autodesk’s API documentation content, there is a distinct preference for the development of ‘plug-in’ applications that run from within AutoCAD’s memory space.  This does make programming easier, and the result more reliable.  Both AutoTURN and Autodesk Vehicle Tracking function in this way. VPath has not been developed in this way due to the requirements of standalone operation and 12d Model interaction.

Component Object Model (COM) Interop is not without its issues.  AutoCAD can often be “not ready” and will reject a COM request. We can only advise that you persist. It does work.

12d Object Selection

Original advice was that screen picking of 12d Model objects was temperamental. With recent 12d Model changes to widget events
(V14.0 C2h +), object picking has become much more stable.

CADD Systems would still appreciate being informed of any poor picking behaviour so that we can investigate the source.

What's New

November 2021

  • VPath 4.1.1 addresses an issue introduced with Microsoft updates KB5006670 and KB5005539, where lines in the Preview Window and Vehicle Editor, are drawn very thickly:

April 2021

  • AutoCAD improvements
    • Path type change from "Steering Path Segments" to "IP Curve"
      • Improved reliability. No longer sensitive to tangency.
    • Additional efforts to stabilise AutoCAD interaction
      •  More stable. Not perfect.
    • Ability to edit the path in VPath
      • Can then be updated in AutoCAD.
  • IP Curve paths
    • Export to a drawing other than the source of the polyline
  • 12d Model
    • Fixed a bug that was still impacting string selection.

February 2021

  • Fix applied to accommodate "Wait_on_widgets" event changes in macro language for 12d Model V14 C2h and later. String picking improves as a result.

July 2020

  • Added Insert Before/After and Delete options for IP Curve IPs and Horizontal Cubic Spline control points.
  • Added Zoom Extents options to Vehicle Swept Paths, individual swept paths, Background Strings and Background Image.
  • Enabled picking AutoCAD polyline in “Direction Of Polyline” and “Reverse Of Polyline”.
  • Fixed inconsistent behaviour when altering the scale of a background image after initial scale setting.
  • More robust AutoCAD detection ensuring options are not available if AutoCAD has no open and active drawing.

Support Details

VPath 4 is provided free of charge. The provision of full technical support is limited to users who are employees of the Department of Transport and Main Roads Queensland or consultants performing work for the department.

For further details, refer to the 'Help > About' dialog in VPath.

To be notified of updates to VPath click on the following link and provide your contact details in the e-mail body:
Register Contact Details

For more information, contact CADD Systems via the Service Centre:

Service Centre
Phone: (07) 3066 2000

If your request is of an urgent nature, could you please follow your email up with a phone call to (07) 3066 2000, as the Service Centre mailbox is primarily for non urgent requests.


The VPath V4.1.1.0 installation is available below. The VPath help file is provided as an optional standalone download if required.

When the VPath help file (CHM) is first downloaded, Windows will regard it as suspect and is likely to present the following message:

To view the help file content, you must remove the tick from the “Always ask before opening this file”.

Likewise, if the CHM file is opened from a network folder, content may be missing, however you may not be presented with the message. In this case, make sure the help file is opened from a local folder on the PC.

This is not the case with the help file installed with the application.


  1. Download the installation folder to a folder on your hard drive. 
  2. If you have a previous version of VPath for Windows, go to 'Control Panel, Add/Remove Programs' and remove it.
  3. Run the installation file “TMR.VPath4003setup.exe”, follow the instructions.
    1. Administrator credentials will be requested.
  4. A program group will be created for All Users - Start\Programs\TMR.VPATH
  5. For a more detailed description of the program, refer to the VPath help file that is accessible after installation.

System requirements:

  • Windows 7 or later

Interoperates with:

  • AutoCAD 2008 or later (including Map and Civil 3D) (AutoCAD® © Autodesk, Inc.)
  • 12d Model V12 or later (12d® Model™ © 12D Solutions Pty Ltd).
Last updated 2 November 2022