Holing through sandstone geology around 50m below Newtown, the two machines have now connected westbound sections of the mainline tunnels between St Peters Interchange and Annandale.

The breakthrough means that tunnelling for the twin 7.5km tunnels – which will connect the new M4 tunnels in Haberfield with the M8 (new M5 tunnels) in St Peters – is on-track to finish this year, according to NSW Acting Deputy Secretary Infrastructure and Place Camilla Drover. More than 90% of the tunnels and ramps have now been excavated.

“We’re another step closer to completing this crucial stage of the WestConnex project, which will link the M4 and M8 tunnels, creating an underground bypass of the Sydney CBD,” said Ms Drover. “This is an exciting milestone for the workforce who have been tunnelling on this project for more than two years and have just two kilometres left to excavate.”

Leading the design and construction of the M4-M5 Link Tunnels are joint venture partners Lendlease, Samsung and Bouygues (LSBJV) with management by West Connex / Transurban. They are creating a western city bypass that will also link with the Rozelle Interchange.

Transport for NSW Chief Operations Officer Howard Collins said: “Drivers using the M4-M5 Link Tunnels will be able to seamlessly move between Haberfield and St Peters in around eight minutes, and a trip between Parramatta and Sydney Airport at Mascot will be slashed by up to 40 minutes.

“There have been 450 contracts signed with NSW subcontractors and suppliers to the value of more than AU$950 million (US$738m).”

The M4-M5 Link Tunnels are scheduled to open to traffic in 2023.