The £110m South Devon Link Road project will link Torbay and Newton Abbot, bypassing Kingskerswell.
A flyover at the Penn Inn Roundabout is currently being finished and is one of the last stages of the project, which began in July 2012.
Project manager Paul Couttie said: "We're confident of hitting December for the completion of the works."
Mr Couttie said: "The general shape is here now. We had a huge, mammoth task in erecting the steel beams that support this road as it comes over the roundabout.
"But we're at a state now where we've got the concrete decking and this road will catapult you to into the Torbay area."
The A380 between Penn Inn, Newton Abbot and Kerswell Gardens, Torquay is one of the most choked up and heavily used roads in the region, carrying over 35,000 vehicles a day.
A major new bypass in Devon will be open by Christmas, according to the county council.