Cornwall Council's cabinet has voted to back £60 million plans to dual A30 at Temple.
The plans would see the stretch of the A30 east of Bodmin turned into a four lane road, the compulsory purchase of land between Temple and Higher Carblake needed for the work to be carried out
The backing means that construction work could start in January 2015.
Half the cost will be paid for by the council, with the rest from central government.
Cornwall Council said the improvements would remove a “major bottleneck” that has a “serious detrimental effect” on business, tourism and the lives of Cornish residents.
Queues of up to nine miles of traffic are common on that stretch in the peak summer months.