Austroads has released new recommendations to update several of its national road design guides, following a detailed review of how well current standards accommodate large freight vehicles.
The research highlights growing gaps between today’s heavy vehicle combinations and the geometric design assumptions many roads were originally built to.
The report, released as AP-R745-25, examines the physical space required for safe and efficient LFV movements.
It specifically looks at turning paths, intersection layouts, lane widths, cross-sections, and roadside elements that influence how longer, more productive combinations behave on the network.
Growing LFV use demands modernised design standards
Austroads Transport Network Operations Program Manager Amy Naulls says recent innovation has increased the diversity and size of vehicles on the road.
“We have seen more larger vehicle combinations and strong industry support for B-doubles and other PBS combinations,” Naulls says.
She says updated guidance will help improve productivity, safety and sustainability outcomes across Australia and New Zealand.
The report notes that newer LFVs, particularly high-productivity PBS vehicles, often exceed the swept path allowances assumed when many intersections, roundabouts and rest areas were originally designed.
This mismatch can result in off-tracking, encroachment into opposing lanes or inadequate clearance on curves.
What the report found about LFV requirements
The document provides a synthesis of LFV performance and design needs based on current PBS data and future vehicle trends.
Key observations include:
- Turning path growth: The report’s diagrams for 30-metre and 36.5-metre PBS combinations (pages 17–19) show wider off-tracking than standard templates allow, especially on tight roundabouts and right-turn lanes.
- Longer wheelbases: The review highlights that many LFVs require minimum curve radii or broader shoulders to maintain stability at low and mid-range speeds.
- Crossfall and grade concerns: Page 24 outlines the need for consistent crossfall transitions, as LFVs experience greater dynamic load transfer on uneven or rapidly changing road grades.
- Rest area capacity: Page 29 shows diagrams comparing parking bay dimensions, with current layouts often incompatible with multi-trailer lengths and manoeuvring requirements.
- Tunnel envelope pressures: The report notes that the Austroads Guide to Road Tunnels should reflect increased swept path envelopes and emergency stopping distances for PBS combinations.
Recommended updates to Austroads design guides
To address those gaps, the report recommends targeted updates to several Austroads documents, including:
- Guide to Road Design Part 3: Geometric Design
- Design Vehicles and Turning Path Templates
- Guide to Road Tunnels
- Guide to Traffic Management
- Guide to Pavement Technology
The research calls for improvements to lane and shoulder widths, intersection geometry, turning paths, rest area layouts and roadside safety features.
These updates would ensure that road corridors are future-proofed for the next generation of LFVs.
Naulls says harmonising geometric design standards will support safer and more efficient freight movements.
She says it will also contribute to national goals such as Net Zero 2050 by enabling more productive vehicle combinations that reduce total truck movements.
Austroads emphasises the need to keep guidance aligned with industry change
“Austroads is committed to ensuring our guidance reflects the capabilities of emerging vehicles,” Naulls says.
She says updating LFV requirements will help designers make informed decisions and ensure road upgrades are aligned with evolving freight tasks.
With freight volumes forecast to keep growing, the updated guidance is expected to support jurisdictions as they plan new corridors, realign existing highways and accommodate PBS growth across regional and urban networks.