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Department of Transport and Main Roads

Guide to Traffic Impact Assessment

The Guide to Traffic Impact Assessment provides guidance for development proponents on how to assess the traffic impacts of a proposed development on the state-controlled road network.

The guide outlines the principles and the framework for undertaking a traffic impact assessment and provides advice on mitigation strategies to address traffic impacts. The guide provides advice for both development proposals assessable under the Planning Act 2016, as well as for major development assessed under other assessment frameworks (usually subject to an environmental impact statement, or a notifiable road use).

Supporting material

Several tools are available to assist industry in understanding and applying the Guide, including answers to frequently asked questions and videos about the guide, intersection delay assessments, pavement impact assessments and road safety assessments.

The Guide to Traffic Impact Assessment Case Studies provide step-by-step guidance for completing a traffic impact assessment in four different scenarios:

  • high density residential development in an over capacity road network 
  • large hardware retailer in an under capacity road network
  • large quarry in a rural area (view video), and
  • small residential development in an under- capacity road network (view video).

The Pavement  Impact Assessment Practice Note provides further guidance on how to prepare a pavement impact assessment, including step-by-step examples for a number of different development scenarios.

The department also can provide road asset data used in traffic impact assessments and information such as marginal cost rates for pavement impact assessments. To obtain access to this data please complete the Road Asset Data Request Form and submit to your local region or

View the embedded videos for further information.

Overview to Guide to Traffic Impact Assessment

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Case Study 1 - Quarry in a rural area

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Case Study 2 - Small residential development

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Intersection Delay Assessment

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Pavement Impact Assessment

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Safety Assessment

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Superseded guide versions

Guide  to Traffic Impact Assessment (commenced July 2017, replaced October 2018).

Contact us

For general enquiries about the guidelines, please contact:

Director (Corridor Management and Protection Unit)
Transport Strategy and Planning Branch
Transport and Main Roads

For technical enquiries please contact your local region.

Last updated 30 July 2019