The A381 is a medium-length A-road in south Devon. It looks like a "long way round" route but there probably isn't a quicker or more direct way between the two ends.
Teignmouth – Totnes
The road starts off as a continuation of the A379 at Teignmouth where that road swings left over the causeway that spans the River Teign. It heads along the edge of the Teign Estuary past numerous camping and caravan sites, and has a nice view. It then meets the primary A380, which it multiplexes with to the next roundabout.
Torquay Road, Newton Abbot
The A381 then heads off right into Newton Abbot, where the A382 departs. It turns to head southwards again and runs back into the countryside through Abbotskerswell. As is common in this part of the world, the road is quite hilly and twisty, but with great views along it. It eventually descends down towards the River Dart, where it meets Totnes.
Totnes – Salcombe
The A381 multiplexes with the A385 over the Dart and past the castle in the centre of Totnes, then heads off to the left. There's then quite a steep climb up the hill before it finally leaves the town behind. After that, there's another drop down into Harbertonford and back up again the other side, before Dartmouth-bound traffic leaves at Halwell along the A3122.
Beyond Halwell, the A381 slopes round the hill towards past the Stanborough Hundred Hotel, and then there's a more straight section of road than previously that heads down towards Kingsbridge. The A381 then multiplexes with the A379 around Kingsbridge, although exactly where is slightly confusing, as various maps have slightly different ideas about where it goes (and road numbers in the Kingsbridge area seem fairly fluid anyway). At any rate, the final section of the A381 runs around the Kingsbridge Estuary before heading into Salcombe, where there are some spectacular views across the river, and of the nearby boating areas. The OS coverage gives up on the A381 just before its final descent down to the village centre, where the only way forward is by boat.
The last descent into Salcombe is marked as the B3204 on most maps.
Originally, the A381 only went from Teignmouth to Kingsteignton where it terminated on the A380. The entire of the rest of the route from Newton Abbot to Salcombe was the B3197. The A381 got as far as Kingsbridge in 1935 and Salcombe by 1961.
See Kingsbridge for the ongoing saga of road numbering in that area.