A13 roadworks to cause traffic chaos in Essex
Motorists face 18 months of disruption on one of the county's busiest roads.
As part of work to improve the A13 between Stanford-le-Hope and Orsett, the road will close completely for 12 weekends, with lane closures and lower speed limits the rest of the time.
The £79m project will start early next year and is due to be completed by autumn 2020.
Thurrock Council, which is managing the scheme, said the effect on road users would be "minimal".
The work - which is being part-funded by DP World London Gateway - will see the 2.3-mile (3.7km) section of the road between the A128 and the A1014 widened from two to three lanes in both directions.
Four bridges will also be replaced, the Orsett Cock roundabout will be widened and new traffic lights will be installed to help manage vehicle flow.
As well as the weekend road closures, there will be a number of daytime restrictions and overnight work.
Once complete, the A13 - which is one of the key routes from Essex to London - will be three lanes in both directions between the M25 and Stanford-le-Hope.
Work to carry out surveys, divert pipework and clear vegetation began in December 2017 but the main body of work will get underway in 2019.
The Conservative-led council said improving the road would "boost the local economy, help businesses to increase productivity, reduce costs and create more jobs".
Councillor Mark Coxshall, portfolio holder for regeneration, said it was "one of the largest local authority-managed road schemes in the country".
"This section of the A13 is currently operating over capacity, with approximately 77,000 vehicles using it daily," he said.
"For most of the works, we will keep two narrow lanes open on the A13 in both directions with a reduced speed limit and camera enforcement in place to ensure the safety of workers and road users.
"Any closures will be advertised well in advance to encourage cross-county traffic to avoid the A13 and use other appropriate routes such as the A12 and A127."