The government has announced its preferred route for a new Lower Thames Crossing, creating a link between the A2 and M25, while reducing the traffic on the Dartford Crossing.
The planned route will run from the M25 near North Ockendon, cross the A13 at Orsett before crossing under the Thames east of Tilbury and Gravesend.
A new link road will then take traffic to the A2 near Shorne, close to where the route becomes the M2.
The preferred route was identified by the majority of nearly 47,000 respondents to a consultation on a new Lower Thames Crossing as the best option for reducing traffic and congestion at the Dartford Crossing, as well as boosting the economy by improving links to London and the Channel ports.
It is expected to carry 4.5m heavy goods vehicles in its first year.
Highways England offered its support to the construction of a tunnel under the river Thames, connecting Tilbury in Essex and Gravesend in Kent.
Transport secretary Chris Grayling said the development could create more than 6,000 jobs and boost the economy by more than £8bn.
He said: “We are making the big decisions for Britain. The new Lower Thames Crossing, and other improvements in and around Dartford and Thurrock announced today, will further strengthen our economy while also creating thousands of jobs.
"Our £23bn investment into our roads is already making a difference, with schemes being completed across the country, including the M1 Catthorpe junction and A556 at Knutsford, cutting journey times for millions of motorists."
Read more: Plans set out for Thames crossing
As well as the Lower Thames Crossing, the government is investing a further £66m to widen the A13 Stanford-le-Hope bypass from two three lanes, which should create 4,000 jobs as well as opening up development of hundreds of new houses.