Summary for Second Edition

Aerial photograph of road

A critical review of Austroads Report AP-R621-20

Revised version published as Austroads Report AP-R647-21 “Management of Traffic Modelling Processes and Applications”


AKÇELIK, R., BESLEY, M., ESPADA, I. and NASH, D. (2021). Management of traffic modelling - a critique of Austroads Report AP-R621-20 (Transport modelling for project managers), 2nd Edition. Technical Note. Akcelik & Associates Pty Ltd, Melbourne, Australia.

Summary for Second Edition

On this page, we present a summary of the findings and recommendations of this second edition of the critical review.

In June 2020, Austroads published Research Report AP-R621-20 (Building Transport Modelling Management Capability) In response to this report, a detailed critique report entitled Transport Modelling for Project Managers - Critique of AUSTROADS Report AP-R621-20 was published in August 2020. 

The critique highlighted key areas of deficiencies of the Austroads report, in particular its traffic model categorisation scheme which formed the basis of the report. This categorisation scheme and various detailed characterisations of intersection and small network modelling techniques were inconsistent and undervalued analytical modelling techniques. These deficiencies in guidance could lead to misinformed decision making in the preparation of modelling briefs and specifications by managers of transport and traffic modelling projects which could have impacts on the efficiency and quality of modelling outputs used in the design and operation of critical traffic facilities.

In response to the critique report Austroads carried out a major revision of Research Report AP-R621-20 and replaced it with Research Report AP-R647-21 (Management of Traffic Modelling Processes and Applications).

In its RoadWatch: News Alert dated 9 March 2021, Austroads noted:

In response to industry feedback, Austroads re-engaged with its member agencies to revise the report. Key updates to the revised edition include:

  • Additional acknowledgements that the traffic and transport modelling industry is constantly evolving and that the Austroads report is reflective of the research and information at the time of development.
  • Additional clarity and transparency on the purpose of the report, in providing high-level guidance to non-modellers while also directing them to other publications / guidelines or subject matter experts where relevant. This included changing the report title to “Management of Traffic Modelling Processes and Applications”.
  • Clearer definition of the terms “traffic” and “transport” as it relates to the report content.
  • Additional explanations accompanying the model categorisation to clearly articulate its intentions and target audience.
  • Revision and update of specific technical information contained in the report, particularly in “Chapter 4 - Intersection Models” by clarifying that the term “intersection models” can contain multiple intersections along a small corridor / network.

“We thank Sidra Solutions for sharing its perspectives and expertise,” said Richard Delplace, Program Manager Transport Network Operations. “We reviewed their feedback in collaboration with the subject matter experts from each of our member agencies and made multiple updates in response.”


The new Austroads report AP-R647-21 was reviewed and detailed responses were included in a second edition of the critique report, now entitled Management of Traffic Modelling - A critique of Austroads Report AP-R621-20A, Transport modelling for project managers, 2nd Edition.

The authors of the critique report and SIDRA SOLUTIONS thank professionals who supported our submission to Austroads, and Austroads for its positive response to our feedback that led to the revision of the report.

Model categories and software assessment

In summary, there have been significant improvements in report AP-R647-21 in removing and clarifying technical aspects of the previous report AP-R621-20 which were criticised. Advising project managers to consult expert model users about the choice of appropriate modelling techniques and software is an important improvement.

However, the criticised Model Categorisation scheme remains unchanged in the new report.  Our disagreement about the "Simulation Model - Intersection Model" dichotomy remains. Our preferred Model Categorisation based on the geographic extent of the area to be modelled and the purpose of model use remains current.

The criticism of lumping together different software packages into forced model categories also remains. A method is proposed for the assessment of model categories and key model features that apply to individual software packages.

Transport and Traffic Model Categories
Assessing Software Packages

Technical details

The first edition of the critique report presented detailed discussions of specific technical aspects of Austroads report AP-R621-20. These included capacity estimation as a function of road geometry, traffic flows and signal timings; modelling of peak demand period; treatment of pedestrians and vehicle classes including bicycles, buses and trams / light rail; and various misleading aspects of the report.

Some detailed technical issues persist including Appendix D that remains unchanged in report AP-R647-21 with misleading information about the capabilities of different modelling techniques.  Refer to Sections 3.3 and 4 of the second edition of the critique report for details.


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