Australia’s longest road tunnel has been proposed after the state government in New South Wales unveiled a proposal to convert two proposed tunnels into one longer tunnel on the Great Western Highway.

In a joint statement, NSW Deputy Premier John Barilaro and Minister for Regional Transport and Roads Paul Toole said investigations are underway for an 11-kilometre tunnel as part of a $2.5 billion project to complete the final 34 kilometre of a modern dual-carriageway link over the entire Blue Mountains between Katoomba and Lithgow west of Sydney.

Already, the government has committed to a 4.5-kilometre tunnel to bypass Blackheath and a 4-kilometre tunnel underneath Victoria Pass – one of the steepest roads in NSW.

Now, it is looking at connecting these into a longer tunnel.

Eastern Tunnel Entrance

One of Australia’s most historic roads, the 201 kilometre Great Western Highway runs in a westerly direction from Sydney to Bathurst and provides a key east-west connection out of Sydney.

Sections of the highway have been progressively upgraded over the past 100 years.

In 2019 the NSW Government committed $2.5 billion to its duplication between Katoomba and Lithgow,

This will complete the final stage of a 130-kilometre upgrade which has taken place over several decades and will delivering dual carriageway on the highway.

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,” he said.

“This is an immensely complex and ambitious plan, but we’re working hard to make it happen because we know what a difference it will make to the lives of commuters, to regional businesses who need access to Sydney and vice versa, to freight companies, to families visiting relatives and to holiday makers.

“The NSW Government is committed to building a safer and stronger regional NSW and this corridor will enhance the state, significantly cutting travel times between the city and the bush.”

Western tunnel entrance

Toole said the solution would link the two tunnels already determined for Blackheath and Mount Victoria to deliver a safer, more reliable connection through the Blue Mountains.

“The NSW Government knows how important this upgrade is to the people who use the Great Western Highway every day and in improving connections between Sydney and the Central West, which is why we committed $2.5 billion to deliver a once-in-a-generation upgrade to this key corridor,” Toole said.

“As part of this upgrade, we’ve already committed to a 4.5-kilometre tunnel to bypass Blackheath and a 4-kilometre tunnel underneath Victoria Pass, one of the steepest roads in NSW.

“We’re now investigating connecting those two proposed tunnels into one longer tunnel. This would be a history-making project, delivering Australia’s longest road tunnel and allow motorists to avoid all the current pinch points from Blackheath in the east to Little Hartley on the western side of Victoria Pass.

“It will also mean less disruption for local residents and businesses during construction and a smoother, safer journey for those travelling underneath Blackheath and Mount Victoria as well as those travelling above.”

Toole said the eastern entry for the proposed tunnel will be on the outskirts of Blackheath to minimise impacts on local homes and be built in a section of National Park land to the south of Evans Lookout Road.

“At the Western end, the portal location in Little Hartley has been modified to improve safety and reduce property impacts in the valley.”

Western tunnel entrance

Transport for NSW is engaging with National Parks about the upgrade’s impacts on land adjacent to the proposed portals. Neither portal would impact the Greater Blue Mountains World Heritage Area, the government says.

Toole said heavy traffic over Easter had reiterated the importance of safe, reliable connections over the mountains.

“This is an immensely challenging project but, once complete, it will deliver dual carriageway in both directions for over 100 kilometres,” Mr Toole said.

“Should our investigations into a long tunnel determine that it isn’t viable, the community can be assured that we would proceed with a tunnel at Blackheath and a tunnel at Mount Victoria.”

Construction on the Great Western Highway Upgrade is expected to start at Medlow Bath in 2022, with the full upgrade expected to be completed within 8 to 10 years.