7.5 km

twin tunnels in Sydney

Providing vital support for the long-term growth of Sydney

The project, completed by ACCIONA with Joint Venture partners Bouygues Construction Australia and Samsung, consists of twin 7.5-kilometre four-lane tunnels creating a link between Haberfield and St Peters by connecting the newly constructed tunnels which connect the M4 and M8.

The project will create a western bypass of the CBD along with numerous benefits; eased congestion, connected communities and more than 11,500 jobs both directly and indirectly. The project will provide vital support required for the expected long-term growth of Sydney’s economy and population.


The M4-M5 Link is being delivered in two parts. Stage 3A is the tunnels connecting the M4 and M8 and Stage 3B is the Rozelle Interchange.


  • By 2031, 40 minutes will be cut from an average peak journey between Parramatta and the Sydney Airport
  • More than 100,000 trips a day are expected on the new extensions of the M4 and M8, removing vehicles which would otherwise clog suburban and city streets
  • Around 4,000 vehicles are forecast to be taken off King Street, with 3,000 fewer vehicles on Sydenham Road each weekday
  • Daily traffic volumes on Parramatta Road between Haberfield and the CBD will be significantly improved with reductions of up to 50% along certain sections
  • Around 2,000 heavy vehicles are forecast to be removed from Parramatta Road east of the M4 Parramatta Road ramps each weekday.

Sustainability initiatives

  • Reduced Carbon emission for the project by 28%
  • Reduced the life cycle impacts of materials by 17%
  • Reduced water consumption by 60% in construction
  • Optimising non-potable water reuse (currently at 62%)
  • 100% reuse of all usable spoil
  • 98% recycling of construction and demolition waste
  • 20% green power
  • 31% supplementary cement material in concrete mixes. 



  • Outstanding International Shotcrete Project of the Year – American Shotcrete Association (ASA)
  • Excellence in Economic Outcomes – Infrastructure Sustainability Council.

General information

  • Location: Sydney, New South Wales
  • Contract: Design and Construct
  • Infrastructure: 7.5km twin tunnels
  • Completion Date: 2023
  • Project Cost –$3.9 billion

Key features

  • The design and construct contract for the M4-M5 Link Tunnels was awarded to the joint venture of Acciona Construction Australia, Samsung C&T and Bouygues Construction Australia (ASBJV) in June 2018
  • 5km twin tunnels, three lanes in each direction
  • Largest road transport infrastructure project in Australia
  • Construction started in 2018 and the project will be open to traffic in 2023
  • Contributes to the $20bn of economic benefits to NSW
  • The travel time between the existing M4 and M8 using the new tunnels is expected to be eight minutes
  • Creates a bypass of 52 sets of traffic lights
  • This project is the most critical component of the 33km WestConnex Motorway, with Rozelle Interchange being the final stage of the WestConnex network.