The second Tyne Tunnel is due to open in February 2011
The final section of a new £260m road tunnel under the River Tyne has been excavated, according to contractors.
Workers have broken through the last concrete wall, making it possible to walk through what will become the second Tyne Tunnel.
Contractors TT2 described the news as a "tremendous moment".
The new tunnel, which links North and South Tyneside, is due to open in February 2011, when the existing tunnel will close for refurbishment.
Trevor Jackson, managing director of TT2, said: "There is still work to do to complete the tunnel structure.
"But to be able to walk from one end of the land tunnel to the other beneath Jarrow really gives a sense of achievement and brings us one step closer to opening the new tunnel to traffic.
"This is a tremendous moment for everyone involved in the project."
David Wood, chair of the Tyne and Wear Integrated Transport Authority, added: "This is an exciting milestone for the project.
"It is incredible to think that the first dig to create the tunnel trench happened around a year and a half ago and we are already refilling the trench above the new tunnel with the soil we removed.
"The process has gone very smoothly and I am delighted with progress."
The existing tunnel, which opened in 1967, carries more than 11 million vehicles a year.
The new tunnel has been built east of the existing site between Jarrow in South Tyneside and Howden in North Tyneside.