Road Safety
Infrastructure Risk Rating Manual for Australian Roads
- Publication no: AP-R587A-19
- ISBN: 978-1-925854-14-5
- Published: 4 March 2019
- PDF (free) Download
Infrastructure Risk Rating (IRR) is a road safety risk assessment methodology that is calculated by coding the following road and roadside features:
- Land use
- Road stereotype
- Lane and shoulder width
- Horizontal alignment
- Roadside hazards
- Intersection density
- Access density
- Traffic volume – rural roads only
- Speed limit – rural roads only.
This manual sets out the steps for undertaking an IRR assessment. It is divided into four parts:
- Identify supporting data sources
- Identify homogenous road sections
- Code road and roadside features
- Calculate IRR score and risk band.
The online map-based tool for calculating IRR, the IRR Tool, can be accessed from irrtool.austroads.com.au
Download the quick user guide to the IRR tool.
- Summary
- Step 1: Identify Supporting Data Sources
- Step 2: Identify Homogenous Sections
- Split roads by land use
- Split roads by road stereotype
- On rural roads, break sections where there is significant change in horizontal alignment
- Consider significant changes in traffic volume
- Consider other factors
- Cluster urban roads with similar IRR attributes
- Step 3: Code IRR attributes
- Land use
- Road stereotype
- Lane and shoulder width
- Horizontal alignment
- Roadside hazards
- Intersection density and access density
- Traffic volume (rural roads only)
- Speed limit (rural roads only)
- Step 4: Calculate IRR Score and Risk Band
- IRR category scores
- Operating Speed Factor (rural only)
- Appendix A IRR Attribute Coding Examples
- A.1 Land use
- A.2 Road Stereotype
- A.3 Roadside Hazards
- A.4 Horizontal Alignment
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