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$20 billion

in economic benefits to NSW


trucks a day removed from Parramatta Road and routed underground

40 minutes

of travel time saved between Parramatta and Sydney Airport

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The challenge

With Sydney’s population estimated to increase by 1.5 million over the next 20 years, with much of that growth likely to occur in Western Sydney, the NSW government needed to develop new road infrastructure to accommodate the swelling demand for transport and road use on Sydney’s motorways.


    WestConnex is an ambitious Sydney road infrastructure program. The construction of a 33km motorway built in four stages will connect the growing population and business centers of Western Sydney to the city’s international airports, central business district and other key places of business across the city. Arcadis was engaged as a key partner, collaborating with multiple stakeholders throughout the course of the project’s delivery of the new Sydney motorway.

    Arcadis drew on its wide range of design, environment and engineering services and expertise in large-scale road infrastructure projects. With an established reputation as a provider of Independent Certification Services around Australia, Arcadis was also engaged to provide independent certification services for the new M8 design and construction component of the WestConnex project in association with APP and SMEC. Arcadis was again engaged to provide Independent Certification Services for the M4-M5 Link Tunnels design and construction component linking the new M4 with the M8.

    Completion of the project presented multiple complexities including constrained interchange sites; sensitive local communities; technically complex structures including four major cut and cover excavations and a substantial underground ventilation structure building; crossing flood catchments; and major utility relocations to build such extensive infrastructure in the heart of Sydney.

The solution

In association with AECOM, Arcadis was responsible for civil, structural and building design of the 5.5km extension of the M4 Motorway from Homebush Bay Drive in Homebush to Wattle Street in Haberfield. This component of the project included a 3.5km tunnel and 1km of above ground surface works with two new three-lane carriageways beneath Paramatta Road and major road bridges including a steel bridge over the existing M4 motorway and bridges at Homebush Bay Drive and the Concord Road Interchange.


    With one of the most experienced and cohesive road engineering teams in Sydney working on the project, the Arcadis team used innovative civil engineering solutions to overcome challenges in completing designs parallel to the planning approval process and traffic modeling and working flexibly to accommodate major changes while keeping up with key project milestones.

    Following the M4 project, Arcadis, in a joint venture with WSP, provided all civil, structural and building design services for contractor John Holland CPB Lendlease in the WestConnex Rozelle Interchange project, considered one of the most complex underground junctions ever built. The project connects the M4-M5 Link to the Anzac and Iron Cove bridges, and the future Western Harbour Tunnel and Beaches Link.

    The design included several key elements of the project from structural and geotechnical works to traffic and intelligent transport systems. Meeting the challenge of having to design multiple tunnels in a small area and designing an interchange with reduced footprint on the surface and moving forward with an all-underground design, Arcadis also successfully ensured that buildings and other structures above tunnel were not damaged as a result of the tunnel build.


The impact

WestConnex is a critical part of a broader plan to get Sydney, and Australia, moving again and is expected to deliver significant benefits to the thousands of people who rely on the roads in Sydney and Western Sydney. Travel times between Parramatta and Sydney’s Kingsford Smith Airport will be reduced by up to 40 minutes while bus travel times between the Inner West and the city will be halved. Furthermore, capacity on the M5 East corridor will be doubled, 52 sets of traffic lights will be bypassed and an estimated 4,000 trucks a day will be removed from Parramatta Road, routing them underground.


    The WestConnex Rozelle Interchange is part of the M4-M5 Link and will provide an underground motorway interchange to City West Link, as well as provide an underground bypass of Victoria Road between Iron Cove Bridge and Anzac Bridge, with links to the future Western Harbour Tunnel. The Rozelle Interchange is being built almost entirely underground, freeing up space for a new 10ha regional park, which will provide local community amenities such as sporting fields, walking areas and open communal spaces.

    These benefits significantly unlock opportunity for neighborhood revitalisation, improvement of north-south travel times for public buses accessing the Western Rail Line at Burwood and other stations, and deliver more than $20 billion in economic benefits to NSW.

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