About 150 homes and businesses will be acquired by the New South Wales Government as part of the latest stage of the Sydney Metro railway project.

Key points: Latest stage of Sydney Metro railway project to include large scale property acquisitions

Latest stage of Sydney Metro railway project to include large scale property acquisitions Sydney to Bankstown line to be shut down for more than six months during construction

Sydney to Bankstown line to be shut down for more than six months during construction Transport Minister admits it will be a "disruptive time" for commuters

Commuters on the Chatswood to Bankstown line will face more than six months of having to take buses instead of trains while the new line is constructed.

But Transport Minister Andrew Constance said it would be worthwhile to get a new train line.

"There will be a period of time, where that rail line will be decommissioned and as a result we will have to manage the commuter needs through that period," Mr Constance said.

"We will work with the community, it will be a disruptive time, I won't sugar coat that, but that's not something that's going to happen in the next couple of years.

"There will be construction disruption through the heart of the city with this project, given the new stops at Barangaroo, Martin Place, Pitt Street, Central."

Extending from Chatswood to Bankstown via the CBD, the second stage railway project will include twin tunnels under Sydney Harbour.

Mr Constance opened the tender process today but did not provide details on the planned acquisitions.

"There are always going to be some sensitivities for business and for home owners and apartment owners," he said.

"That's why we get a professional team in place to be able to go and do that work."

'Commuters rightfully frustrated and shocked'

Greens Mp Mehreen Faruqi has spoken out against the government's Sydney Metro plan. ( Supplied )

Greens Transport spokeswoman Mehreen Faruqi has called on the Government to justify shutting down the Bankstown line for six months.

"Commuters would be rightfully frustrated and shocked to hear that the great apparent transport fix for their area is to shut down and privatise their existing rail service," she said.

"The Government has never given any detailed evidence of why shutting down and privatising the Bankstown line is the way to fix the train network, rather than actually expanding it to new areas or putting higher frequency trains on other lines.

"This whole project will cost upwards of $20 billion and it's about time the Government actually explained themselves."



Final costs to be announced 'very soon'

Mr Constance said he could not say how much the second stage would cost, but said the original estimate for the Sydney metro overall cost was between $9.5 billion and $11 billion.

"We're obviously engaging with the private sector, we're in the final stages of the processes around the business case, for that reason we want to get the best value for money for tax payers," he said.

He said the metro was part of the Government's program of improving NSW infrastructure and the line would be the centrepiece of a transformed city and state.

Andrew Constance says the Sydney Metro project would encourage people to leave their cars at home. ( ABC News )

"We're going to get a final costing very soon," Mr Constance said.

Mr Constance said since the original cost range was released, the Government had done geotechnical work which revealed new challenges.

"There are different tunnel boring techniques which need to occur under the harbour because of the very nature of the water and the soaking into the sandstone."

Mr Constance said the first of five tunnel boring machines would be in the ground before the end of 2018 to deliver new twin railway tunnels from Chatswood to Sydenham.

The Government aims to open the Sydney Metro by 2024.

Mr Constance said the train was a "game changer" and Australia's first driver-less "super train".

"We are going to see 45,000 passengers per hour, moved on the metro network, this compares to 24,000 on the existing network."

He said the network would encourage people to leave their cars at home.

"We're very keen to get people on trains, that's why we're building this type of train, this is a high frequency turn up and go service."