An underground train line to slash commute times between Parramatta and the Sydney CBD to 20 minutes will be planned under $3 billion of funding reserved in the New South Wales budget.

“This project will redefine how we get around Sydney and will double rail capacity between the two city centres,” Transport Minister Andrew Constance said.

He called the line “a true city-shaping investment that will serve generations to come.”

Treasurer Dominic Perrottet handed down the 2018-19 budget on Tuesday, declaring it was “building for today and delivering for tomorrow”.

The election-year splurge focuses on infrastructure and cost of living measures ahead of the state poll in March.

It includes a $3 billion “reservation” for Metro West design, planning approvals, land acquisition and early works and tunnelling.

Another $28.1 million will fast track the final business case, Mr Perrottet announced on Tuesday.

The line will connect the CBD with Parramatta and Westmead, with stations at The Bays Precinct and Sydney Olympic Park.

The line will connect the CBD with Parramatta and Westmead via The Bays Precinct and Sydney Olympic Park. Photo: Transport for NSW

“We have already begun the work to determine the best underground route between the Sydney CBD and Greater Parramatta with a program of geotechnical drilling, which will continue,” Mr Constance said.

Metro West is expected to be completed sometime after 2025, doubling the capacity of the crowded T1 Western Line and freeing up other services.

It will have an underground interchange with T1 at either Westmead or Parramatta.

Earlier this year it was revealed Metro West would also link to a suburban station at Concord West or North Strathfield.

Other stations at Camellia/Rydalmere, North Burwood/Five Dock, Kings Back and Pyrmont are being considered.

The project would service the extra 420,000 people expected to move into the corridor over the next 20 years.

Sydney Metro will cost the government $4.3 billion in 2018-19, the budget showed.

That includes $2.4 billion on Metro Northwest, linking North West Sydney to Chatswood. The funding also includes $1.9 billion on Metro City and Southwest, linking Chatswood and Bankstown.

Opposition Leader Luke Foley said the Metro West would not be delivered for another decade if the Coalition is re-elected in March.

“They reserve $3 billion for a $16 billion project,” Mr Foley told reporters on Tuesday.

“And I’ve been honest here, Labor will accelerate it because we won’t do the Northern Beaches tunnel. We won’t do the Bankstown conversion, we’ll free up billions to plough into accelerating the delivery of a new fast rail line between Parramatta and the Sydney CBD, the number one transport priority.”

Infrastructure spend

The NSW government’s total infrastructure spend is slated to hit $87 billion over the next four years, with $51 billion of that on roads and rail.

NSW Treasurer Dominic Perrottet with the 2018-19 budget. Photo: AAP

The government is yet to complete any of its signature infrastructure projects, nine months out from the election.

“That can take time and can be politically challenging, we accept that,” Mr Perrottet told reporters.

“If you look across the board, never before have we seen this construction revolution happening.”

New healthcare facilities will be built with $8 billion over four years, and $6.8 billion will go towards school infrastrcture.

The $4.2 billion sale of the state’s share of Snowy Hydro will be invested in regional infrastructure, the details of which Mr Perrottet will announce later this year.

Mr Perrottet revealed a budget surplus of $3.9 billion, despite losing billions in stamp duty revenue.

The surplus will average $1.6 billion over the next four years.