The 110 million pound 5.5km long dual carriageway has been built to ease traffic between Newton Abbot and Torbay.
The opening of the road had been kept a secret to avoid any problems caused by hundreds of drivers wanting to be the first on the road.
The scheme started in 2012.
Majority of Devon MPs back assisted dying bill
Just three of Devon's 13 MPs voted against the bill
Crime panel member calls for commissioner to resign
It's in the wake of the suspension of acting Chief Constable Jim Colwell
City footballers take time out to spread some festive cheer
Exeter stars bring joy to children in hospital
Calls for more control over spending
Many projects coming in over budget
Election cycle change thrown out in Plymouth
Annual elections will still be held in the city
