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 Albert Wong by e-mail or on (08) 9323 4153.
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.
MRWA Supplement to Austroads Guide to Road Design
Part 1: Introduction to Road Design
This Supplement has been developed to be read in conjunction with Austroads Guide to Road Design (GRD) Part 1: Introduction to Road Design (2009), 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.
1.4 Parts of the Guide to Road Design
Road Designers need to have a sound understanding of all Parts of the Austroads Guide to Road Design and the relationships between them, as well as the relevant Western Australian requirements. Designers are also referred to other Austroads Guides, including the Guide to Traffic Management and the Guide to Road Safety, which contain a wealth of useful information.
The philosophy and principles set out in the suite of Austroads Guides, and Main Roads Supplementary Information, underpin the creation of a successful, site-specific design solution.
Designers choose the features of the road and dimensions of its elements based on technical guides, calculations and their own experience and judgement. However, a very important principle in choosing these dimensions is to avoid combinations of minimum or limiting values of different design elements as this has the potential to quickly reduce the inherent safety of the overall solution.
The practice of good road design, especially under constraints, involves judgement as well as calculation. It involves compromises between conflicting goals. Experience assists the Designer to arrive at an appropriate balance that cannot be met by a system of mathematical rules alone. The Austroads Guides and the Main Roads Supplementary Information give ranges of values within which the Designer has reasonable flexibility to produce an appropriate design solution for a specific problem, whilst retaining a reasonable overall level of uniformity.
3.3 Context-Sensitive Design
Context-Sensitive Design is explained in greater detail in Austroads Part 2: Design Considerations where there is reference to the Design Domain and Extended Design Domain. A value outside the Normal Design Domain may only be used with the explicit approval of the Manager Road & Traffic Engineering, supported by a documented risk assessment that fully justifies the use of that value.
Main Roads has no supplementary comments for this section.
Project Managers and Designers are referred to Austroads Part 8: Process and Documentation (2009) for expanded information relating to this subject.