MRWA Supplement to Austroads Guide to Road Design - Part 2

Document No:  D11#308687
Revision:  1A
Date amended:  12-Jul-2016

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The information below is intended to reflect the preferred practice of Main Roads Western Australia ("Main Roads"). Main Roads reserves the right to update this information at any time without notice. If you have any questions or comments please contact Steve Curgenven by e-mail or on (08) 9323 4415.

To the extent permitted by law, Main Roads, its employees, agents, authors and contributors are not liable for any loss resulting from any action taken or reliance made by you on the information herein displayed.

Revision Register


Ed/Version Number Clause Number Description of Revision Date



Guideline Developed. 09-Dec-2011 
​1A​All​Contact person changed to Steve Curgenven​12-Jul-2016

Table of Content

MRWA Supplement to Austroads Guide to Road Design -

Part 2: Design Considerations

This Supplement has been developed to be read as a supplement to the Austroads Guide to Road Design (GRD) Part 2: Design Considerations (2006), a copy of which can be purchased via the Austroads website.

In Western Australia, state-based information, on this website and elsewhere, takes precedence over Austroads Guides and Standards Australia Standards. National Guides and Standards take precedence over International Guides and Standards, unless specifically stated otherwise.

This Supplement has the same structure as the equivalent Austroads Guide and only additional requirements, clarifications, or practices different from Austroads appear. Where appropriate, this Supplement may also contain additional sections and figures not covered by Austroads, but the numbering sequence found in the Austroads Guide remains. Figures and tables in this Supplement replace those with the same figure or table number in the equivalent Austroads Guide.


Main Roads has no supplementary comments for this section.



2.2 Normal Design Domain

The desirable lane width for rural and urban roads is 3.5m. 

Note that the reference to Section 11.2 of the Guide to the Geometric Design of Rural Roads, 2003 has been superseded by Section 4.2.4 of the Austroads Guide to Road Design Part 3: Geometric Design, 2009 and the Main Roads Supplementary Information. 

Section 4.2.4 defines the practical upper limit of lane width for a rural road as 3.7m, and no longer refers to a practical lower limit of 3m. Instead, it describes circumstances where narrower lane widths may be considered. In Western Australia Table 4.3 Main Roads Supplement to Austroads GRD Part 3: Geometric Design is still used as the primary guide for determining lane widths.
The Table is based upon previous Austroads and Main Roads guidelines but includes an alternative definition for Design AADT (Annual Average Daily Traffic). 




To the main factors in intersection safety, add:

    • Cycling / pedestrian facilities.


A discussion on context sensitive design can be found on the US FHWA web site at



Replace the reference to the Austroads Guide to Traffic Engineering Practice Part 2, Roadway Capacity (1988) with the Austroads Guide to Traffic Management, Part 3, Traffic Studies and Analysis (2009).