Transport Minister Jo Haylen said new metro trains are now travelling in the 15.5-kilometre twin metro railway tunnels, which extends the Metro North West Line from Chatswood Station to Sydenham Station, as part of a rigorous testing and commissioning program. 
 
"This is an important milestone. We have always said we’d back good projects no matter whose idea it was – this is one of them and it’s what the Sydney Metro project looks like at its best. 

“Having a train travel under our harbour is an exciting and historic first step but more importantly, it means that more people can catch a train through the city and it will improve the broader rail network once the City Metro is ready to take passengers next year.”

“I want to make sure that the Sydney Metro project delivers genuine improvements to transport services like this for passengers and for taxpayers."

This is the first railway crossing below Sydney Harbour and delivers a critical connection into our city from Sydney’s north.

Next year, metro trains will move more people across the Harbour in peak hour than the Sydney Harbour Bridge and Sydney Harbour Tunnel combined, taking significant pressure off Sydney’s roads and existing rail network.

Sydney Metro CEO Peter Regan said on-track train testing and commissioning will continue throughout 2023, ahead of passenger services starting through the Sydney CBD in 2024.

“The first stage of testing is completed at low speed, with trains manually driven at a maximum speed of 25km/ph,” Mr Regan said.

“Gradually, we see the trains move into high-speed testing, where the trains reach a maximum speed of 110km/ph.

“Each train will also undergo acceleration and braking testing on the newly built track and complete a series of system checks to ensure it can perform reliably under operating conditions.”  
 
In 2024, Sydney city will be more connected and easier to move around, with 7 new underground metro stations and faster travel times, including from Central Station to Chatswood Station in 15 minutes, from Martin Place Station to Sydenham Station in 11 minutes and from Victoria Cross Station in North Sydney, below Sydney Harbour, to Barangaroo Station in just 3 minutes. 

https://www.nsw.gov.au/media-releases/metro-milestone-unlocked-as-trains-start-testing-under-sydney-harbour