This article is about the current A378, a road between Langport, near Yeovil and Taunton. For the original, a small road in Exeter between Cotfield and Pinhoe, see A378 (Exeter).
The A378 is a reasonably short road in central Somerset, which begins on the A372 in Langport where that road turns off to the right as it heads west. On the A378, we immediately pass under a railway bridge before turning west as well and passing through the oldest part of the village, with the church up to the left. Then we cross the River Parrett on Great Bow Bridge before emerging into farmland. However the farmland is short lived as we pass through the large village of Curry Rivel, with the B3168 turning off to the left here, heading south across the Levels. The road here runs along the crest of a long hill separating the River Isle and the West Sedgemoor drainage channel. It is therefore relatively flat, but also affords views of the surrounding areas if you can see through the hedges.
After passing Fivehead, the road drops steadily down the hill, onto the Levels, running for a while at less than 10 m (33 ft) above sea level. It then climbs again, to the dizzy altitude of 17 m (56 ft), before reaching the next village, Wrantage. This is little more than a scattering of houses along the roadside, where the road bears right and we climb away from the lower land to reach a T-junction on the A358 where the A378 terminates. This last section feels quite narrow compared to some other parts of the route, perhaps belying its B-road origins.
What is now the A378 used to be part of the B3153 – although the easternmost section in Langport was originally the A372 for a few years, brfore that road was diverted away from the village centre. However, in 1935 (long before the current A378 came into existence) there was talk of diverting the A372 along this route instead of into Bridgwater. For some reason this plan was not approved, and it remained the B3153 until the 1950s.