Tonkin Highway Extension and Thomas Road Upgrade

Perth’s south-east corridor, home to fast-growing communities like Byford, Armadale, Kelmscott and Gosnells, is currently impacted by high volumes of heavy vehicles and through-traffic travelling to and from the South West and Wheatbelt regions.

The Tonkin Highway Extension and Thomas Road Upgrade will provide safer, more efficient travel for road users and heavy vehicles, reduce congestion, and improve connectivity between current and future residential, commercial, and employment areas.

These projects are being delivered together due to the timing of development and delivery, overlap of stakeholders and geographical location.

Tonkin Highway Extension

This project involves a new 14 km four-lane dual carriageway between Thomas Road and South Western Highway. It includes:

• Principal Shared Path (PSP) along the eastern side of the highway for the full 14 km, with connections to Thomas Road, Orton Road, Bishop Road, Mundijong Road and South Western Highway
• Five underpasses and a footbridge at Orton Road for safe crossing by pedestrians, cyclists
• Grade-separated interchange at Bishop Road to improve traffic flow and safety
• Roundabouts at Orton Road, Mundijong Road and South Western Highway
• Underpasses at Abernethy Road and Shanley Road to support vehicle, pedestrian, cyclist, and horse movements
• Underpass at Gossage Road to support pedestrian, cyclist and horse movements
• Rail bridges at Bishop Road and Wright Road
• Noise and visual screening walls, lighting throughout, and improved local road access including emergency egress

The project also caters for recreational needs by supporting the region’s equestrian network with several dedicated horse underpasses and connections.

Thomas Road Upgrade

This upgrade covers the duplication of 4.5 km of Thomas Road between Kargotich Road and South Western Highway, and includes:

• A new grade-separated interchange with Tonkin Highway to improve traffic flow
• A new 4.5 km shared path on the southern side
• A signalised equine crossing connecting Byford and Darling Downs bridle paths
• Intersection upgrades, including:
• New roundabouts at Kardan Boulevard and Masters Road/Malarkey Road
• Left-in/left-out access at Ballak Place and Briggs Road
• Cul-de-sacs at Hopkinson Road (north and south of Thomas Road)
• New traffic signals at Plaistowe Boulevard
• Reconstructed intersection at Wungong South Road
• Realignment of the equine path network north of Thomas Road to maintain connectivity

 

Speed limit reductions

Tonkin Highway and Thomas Road

 From 28 July 2025 to project completion

Speed limits will be reduced to 60km/h on Tonkin Highway, between Thomas Road and south of Rowley Road and on Thomas Road between Masters Road and Ballak Place

Mundijong Road

 From 26 June 2025 to project completion

Speed limit will be reduced to 60 km/h on Mundijong Road between Kargotich Road and Adonis Street.

 Community Information Sessions

We’d like to thank everyone who joined us at recent engagement events, including the SJ Farmers Market and our Community Information Session, where we connected with more than 240 local residents and stakeholders.

In addition, our team recently attended the Serpentine Jarrahdale Career & Enterprise Expo at Byford Secondary College. Across two days, we engaged with over 1,800 attendees, including students, parents, job seekers, and community members, promoting project awareness, job opportunities, and local career pathways.

Your valuable feedback and the insightful conversations were greatly appreciated. Further sessions will be scheduled in the coming months.

 Ongoing engagement

We are working closely with the Shire of Serpentine Jarrahdale and have set up or attend the below working groups at this stage to understand local context and get feedback from key community members and stakeholders. 

• Shire of Serpentine Jarrahdale Technical Working Group
• Environmental Working Group
• Equine Working Group

 

Delivering 14km of new highway and upgrading Thomas Road is a transformational investment in Perth’s south east. It will reduce congestion, improve safety and unlock access to freight routes and employment hubs – supporting METRONET, Westport, and the long-term growth of our WA.

But large-scale infrastructure must also be delivered responsibly.

That is why this project is underpinned by rigorous environmental planning, community engagement and sustainability principles, designed not just to reduce impacts, but to leave a positive legacy.

 Responsible Vegetation Clearing and Rehabilitation

To deliver essential infrastructure, some vegetation clearing is required. We know this can raise community concern, and we want to be clear:

Clearing is being minimised wherever possible and carried out in strict accordance with environmental approvals.

The project has obtained approvals  under the Environmental Protection Act 1986 and the Environment Protection and Biodiversity Conservation Act 1999, the clearing and construction is subject to the conditions of the approvals.

Key commitments include:

• Vegetation will only be cleared where absolutely necessary
• All unsealed disturbed areas will be rehabilitated and revegetated using a mix of engineered treatments and planting native species.
• Rehabilitation design is underway to maximise opportunities for restoration and biodiversity

Fauna crossings will be installed at waterways to maintain habitat connectivity.

 Designing with the Environment in Mind

The project team is actively working to reduce the clearing of native vegetation by realigning roads, protecting trees near work zones where safe, adjusting locations of drainage basins and shared paths.

 Flora, Fauna and Heritage Protection

We’ve engaged environmental specialists to assess, monitor and manage impacts on local ecosystems. This includes:

• Black Cockatoo habitat hollow inspections
• Qualified fauna handlers onsite during clearing to safely relocate fauna

We’re also progressing positive environmental initiatives: 

• Collaborating with the Kaarakin Black Cockatoo Conservation Centre to provide cleared native vegetation (e.g. banksia cones, eucalyptus branches) to assist in Black Cockatoo rehabilitation. 
• Grass tree salvage and replanting within the road corridor.

 Protecting Aboriginal Heritage 

Five Aboriginal Heritage sites are located within the project area. We have received approval under Section 18 of the Aboriginal Heritage Act 1972 to manage these areas respectfully, including salvaging significant items where required and engaging Traditional Owners to monitor ground disturbing activities. 

 Environmental Working Group 

To ensure collaboration and transparency, the project team has established an Environmental Working Group (EWG) with stakeholders including the Shire of Serpentine Jarrahdale. 

The EWG helps to: 

• Share local environmental knowledge
• Provide feedback during project design and delivery
• Raise environmental concerns and community priorities 

We thank all members for their contributions and look forward to continued collaboration. 

 Driving Sustainability and Innovation

The project is embracing sustainable construction by:

• Reusing surplus materials from other infrastructure works
• Prioritising the use of replacement and recycled materials where safe and suitable
• Reducing waste and conserving resources

Examples being explored include:

• Recycled road base, crushed concrete, brick and tile for sub-base and embankments
• Recovered sands and innovative materials
• Recycled plastic products for temporary works and furniture

All materials undergo laboratory and field testing in line with Main Roads and Australian Standards to ensure safety, quality and performance.

 

 

The Tonkin Extension Alliance is currently undertaking market research to identify priority areas for material use and uncover new opportunities for sustainable sourcing.

If your organisation has innovative ideas, materials, or sustainability initiatives that could support this vision, we’d love to hear from you.

 Project information

• Project Update - July 2025 - PDF (483 KB)
• Project Update - June 2025 - PDF (508 KB)
• Project Update - March 2025 - PDF (582 KB)
• Frequently Asked Questions - August 2024 - PDF (220 KB)
• Project Update - August 2024 - PDF (449 KB)
• Project Update - April 2024 - PDF (388 KB)
• Project Update -  February 2024 - PDF (471 KB)
• Access and Connectivity Map - PDF (5.09 MB)
• Project Update - June 2023 - PDF (6.38 MB)
• Project Update - September 2022 - PDF (1.29 MB)
• Project Update - January 2021 - PDF (2.04 MB)
• Project Update - October 2020 - PDF (1 MB)
• Project Overview - June 2020 - PDF (2.38 MB)

Fact Sheets

• Environmental Management – June 2025 - PDF (492 KB)
• Managing Construction Impacts – June 2025 - PDF (376 KB)
• Managing Noise – June 2025 - PDF (529 KB)

 Media Statements

• Joint Media Statement - Contract awarded for transformational Tonkin Highway project - 31 January 2025
• Joint Media Statement - Request for proposal issued for Package 2 Of Tonkin Highway Extension and Thomas Road Upgrade - 10 July 2024
• Tonkin Hwy Extension and Thomas Rd Upgrades continue progress - 22 March 2024
• Joint media statement - Expressions of interest called for Tonkin Highway Extension - 27 November 2023
• Industry workshop starts search for Tonkin Highway Extension contractor – 21 January 2021
• Roads budget delivers congestion busting solution and WA jobs - 9 May 2019

 Funding

The $755 million project is jointly funded by the Federal ($604 million) and State ($151 million) Governments. $290 million is also allocated to upgrade Thomas Road, bringing the total funding commitment to $1.045 billion.