Government agency Highways England submitted the DCO application for the A585 Windy Harbour to Skippool Improvement Scheme earlier this week.
The plans include the new 5km link, four new junctions, and two bridges.
The Planning Inspectorate has 28 days in which to consider whether to accept the application for examination.
Last week, Highways England applied to PINS for a DCO to build a dual carriageway road tunnel close to Stonehenge in Wiltshire.
In August, the agency submitted plans for the creation of a dual carriageway on another section of the A303 north of Yeovil.