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.
City lose final match of the season
Match Report: Exeter City 1-2 Oxford United
Man dead due to 'bad batch' of herion
A major incident was declared in North Devon
Teen pregnancies falling in Devon
Number has been broadly trending down since 2015
Dental van on way to Devon to help tackle treatment crisis
It will help tackle treatment crisis in hard-to-reach communities.
Misconduct inquiry into suspended chief constable suspended
Frustration at pace of investigation
