|Length:||13.8 miles (22.2 km)|
|Meets:||A386, B3212, unclassified|
|Route outline (key)|
The B3357 heads east from Tavistock onto Dartmoor.
The road starts to the east of Tavistock town centre by turning off the A386 just by that road's bridge over the River Tavy, a river our road never crosses. We head east out of town and climb along a narrow road between high hedges before the road widens out and becomes more open after entering Dartmoor National Park.
The road continues to climb and presently crosses a cattle grid to become an unfenced road across the open moorland. It goes over the brow of a hill before descending into the hamlet of Merrivale, where we pass the Dartmoor Inn and cross the River Walkham, a tributary of the Tavy. There's another steep climb on the other side and we cross another cattle grid to reach Rundlestone. Here a spur of the B3357 turns right to follow a winding, wooded route into Princetown. After passing Dartmoor Prison it runs along the town's main street to end at a mini-roundabout on the B3212.
Returning to the mainline of the B3357 we continue east and descend to Two Bridges, where the B3212 comes in from the right. The B3357 is the dominant number in a multiplex over the West Dart River (not one of the original bridges) which lasts until the B3212 turns left on the far side of the valley. We now follow the river downstream, albeit not particularly closely: the river follows a winding course to the south whilst the road follows a straighter course across the moor.
There's another short section of open moorland between two cattle grids as we pass to the south of Belliver Tor but the majority of this section of road is lined with walls. After passing the turn for Hexworthy there's another cattle grid for no apparent reason followed by a steep descent into the valley of the East Dart and the hamlet of Dartmeet. At the old, narrow bridge over the river the B3357 ends, with the road ahead through Poundsgate into Ashburton unclassified and prohibited to buses and wide vehicles: the road crosses the River Dart twice more, at New Bridge and Holne Bridge, which are older and narrower still than the bridge at Dartmeet.
In the 1970s the Dartmoor section of the A384, from the A386 in Tavistock to the A38 in Ashburton, was renumbered as an extension of the B3357 (keeping the spur), then the road was declassified east of Dartmeet in the 1980s, giving the road its current length.