The two week closure of the A381 at Halwell is set to cause chaos between Kingsbridge, Dartmouth and Totnes, it is feared.
Devon County Council has announced it is closing the busy main road at the point down from the village church at Halwell from Tuesday 9 May until Tuesday 23 May.
The official diversion will lead traffic from Kingsbridge to Sorley Cross through to Loddiswell, along the A3121 to the A38 turn off at Wrangaton, then onto the A385 South Brent turning to Dartington and Totnes – and vice versa.
According to Google Maps this will add an extra 10 minutes onto the journey time as the route is some four miles longer than the Halwell route.
It is expected that drivers with local knowledge will use other, less well known routes.
Local people travelling towards Totnes from Dartmouth will make their way to the town through a network of narrow lanes, while those travelling towards Kingsbridge can take the coastal route which leads to the villages of Chillington, Frogmore and West Charleton.
The 24/7 road closure is due to problems with the culvert which crosses the road at Halwell and is linked to the drainage system.
Temporary traffic lights have been in place on the northbound side of the A381 for a few weeks now but Devon County Council says recent frequent heavy rainfall has made the situation worse.
The rain has resulted in the road surface crumbling and a dip in the road to appear in that area.
In a letter to nearby residents, the council said: “This has now reached the point that the road through Halwell will have to be closed for this culvert to be inspected fully and to be replaced and the road surface reinstated.”
The council also advises that should the weather continue to be adverse, the road may have to be closed for safety reasons at very short notice.