The NSW Government is set to build Australia's longest road tunnel under the Blue Mountains.
The 11km stretch of tunnel between Blackheath and Mount Victoria could end up ballooning to $8billion or $730,000 per metre.
Regional Roads Minister Paul Toole said the tunnel, which forms part of the Great Western Highway upgrade, would be 'Northconnex but better' for motorists bound for the state's central-west.
Deputy Premier John Barilaro said the proposed tunnel would transform the state by better connecting the Central West to the East Coast.
'We have already committed to tunnels at Blackheath and Mount Victoria - this proposal would see those tunnels joined together, creating the longest road tunnel in the country,' Mr Barilaro said.