What would be Australia's longest road tunnel has been proposed as part of the upgrade of the Great Western Highway.

Investigations are now under way to make an 11km tunnel the central component of the upgraded highway between Katoomba and Lithgow.

Deputy premier John Barilaro said the proposed tunnel would transform New South Wales by providing better connections betwee the Central West and 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.

Completing the Katoomba to Lithgow section would deliver the final stage of a 130km upgrade as part of a multi-decade programme of works.

Minister for Regional Transport and Roads Paul Toole said the plan would link the two tunnels already determined for Blackheath and Mount Victoria to deliver a safer, more reliable connection through the Blue Mountains. “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.”