Dorset County Council has applied for pinch point funding to rebuild one of the country's busiest roads.
The council is arguing that repairing the A338 Bournemouth Spur Road is no longer cost effective.
It has also got backing from the Bournemouth Chamber of Trade which described the dual carriageway as "20 years past its safe use-by date".
The council has applied for about £20m from the government's £170m Pinch Point Fund.
The project would rebuild a 5.5 miles stretch from the Ashley Heath interchange to the Blackwater junction which carries 56,000 vehicles a day.
Miles Butler, the county council's director for environment, said: "It will be a major piece of engineering work and it will cause some disruption, but it is better to have disruption in one year, rather than having maintenance on that every year for the foreseeable future."
A previous bid for £20m funding for repair works on the A338 was turned down by the government in 2011.
