The B3413 currently holds a number that hides the once important status of this road that was the former A38 through Plymouth, although before that it had been the A374, A3078, and B3246.
From Forder Valley the route leaves the A38 at a roundabout junction and runs along the bottom of Forder Valley as an S2, where it TOTSOs left at a light-controlled junction with the start of the B3432. From here the road takes a very steep climb up the side of the valley to Crownhill. Various local roads connect via T-junctions but at Crownhill there is a junction with the A386 and B3373 which would be a cloverleaf were it not for the roundabout connecting the B3413 to the latter. From here the road was D2, but has now been hatched down to D1 through several traffic-light junctions until it once again meets the A38 at a dumbbell junction.