Councillors said the upgrade was needed urgently to support investment
A scheme to widen the main road to the port of Immingham has been awarded £110m of funding, paving the way for thousands of new jobs to be created.
Work to turn the A160 into a dual carriageway is now expected to start within two years.
Councillors had called for the plans to be approved, saying up to 15,000 jobs at schemes planned for the area were at risk if a decision was not made soon.
A scheme to improve the main traffic link through Hull has been put on hold.
The decisions have been made by the government's Yorkshire and Humber Regional Transport Board.
The approval of the Immingham scheme has been welcomed by councillors and businesses.
Value for money
Port-based development company Able UK is one of the businesses with plans for the area.
Mark Kirk, leader of North Lincolnshire Council, said: "Their proposal is to create 5,000 jobs in the near future and potentially that is going up to 10-15,000 jobs.
"The one thing that it did need was to clear that one small blockage which was the A160."
In Hull, a stretch of road along the A63 from Porter Street to Myton Bridge was to be widened to ease congestion in the city centre.
Work on the £5m scheme was expected to start in 2012 but it has been postponed by the regional transport board.
The board said the project in its current form did not offer enough value for money and would have a low impact on the region as a whole.
Chris Glen, from the Federation of Small Businesses, said a lot of planned regeneration in Hull was dependent on the A63 scheme going ahead.
He added: "It's important for Hull and the whole region."