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.
Plumes of smoke seen over Exeter
Fire crews tackling blaze in a field
£500k for new homes for Torbay and Afghan families
More than 160 are in temporary accommodation
Government halts protection work on Dawlish mainline
'This is a massive blow'
Three people charged with attempted murder
Two men and a woman appearing at Plymouth Magistrates'
Body found in Cornish woodland
Death is suspicious
Costly Plymouth road project sparks council row
City growth vs. disruption
