The NSW government has committed to building Australia's longest road tunnel in the Blue Mountains.
An 11-kilometre tunnel from Blackheath to Little Hartley has been confirmed as the preferred option in the Great Western Highway upgrades to improve travel across the mountains.
The highway is one of only two roads across the Blue Mountains connecting the central west with the state's capital, and communities in western areas have long called for an upgrade.
The state government had previously committed to building two smaller tunnels across well-known choke points at Blackheath and Mount Victoria but started investigating the possibility of one longer tunnel last year.
The tunnel will be part of the now $8 billion Great Western Highway upgrade which is set to duplicate the 34km of road from Lithgow to Katoomba with dual carriageways.
Deputy Premier Paul Toole said the tunnel and upgrades would take 30 minutes off travel times "on a good day".
"This is going to make a huge difference for people travelling to and from the central west and also through the mountains," he said.
The tunnel is set to travel 100 metres underneath Mount Victoria and 30 metres below Blackheath.
"It's exciting to know that this project is going to become a reality … for a long time this project has been put in the too-hard basket," Mr Toole said.
Construction on the road is set to start in early 2023 with work on the tunnel section to start at the end of 2024 and be operational by 2027/28.
The project has raised serious concerns about Aboriginal heritage and platypus populations in the Lithgow region.
