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 fairly short road in central Somerset, linking Langport with the county town of Taunton.
Great Bow Bridge
The route begins at a TOTSO on Somerton Road to the north-east of Langport town centre, where the A372 turns off to the right for Bridgwater. The mainline through the junction sees the A378 begin, signed for the town centre and Taunton, but with warnings of a weight limit and low bridge ahead. The reason for the low bridge warning become apparent almost immediately, as the road passes under the Reading-to-Taunton railway line before turning west and passing through the oldest part of the town, with the All Saints' Church in the historic centre accessible via a road appropriately named The Hill to the left. Passing through the town along Bow Street, the road is narrow enough not to have central markings. Before leaving the town the reason for the weight limit also becomes apparent, as we cross the River Parrett on Great Bow Bridge.
After leaving the town, it is only a short drive across farmland to the large village of Curry Rivel. Here, the B3168 turns off to the left, heading south across the Somerset Levels towards the quaintly-named villages of Hambridge, Westport, and Puckington, and ultimately Ilminster. 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 through the village of Fivehead, the road drops steadily downhill, 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 we bear right and climb away from the lower land to reach a T-junction on the A358. This is where the A378 terminates, about three miles east of Taunton. A right-turn will take you towards that destination as well as the M5, while a left-turn will head south-east towards Ilminster and the A303.
What is now the A378 used to be part of the B3153 from Ash Cross to Castle Cary via Langport and Somerton, and some of the narrower sections of the route perhaps bely its B-road origins.
Under the 1935 Road Numbering Revision (long before the current A378 came into existence), there was talk of diverting the existing A372 along this route from Langport towards Taunton, instead of Bridgwater. For some reason this plan was not approved, and the section of the B3153 to the west of Langport retained its B-number until being upgraded to its current status during the mid-1950s.
The other point to note is that the easternmost section of the A378, running along North Road, Moor Close, and onto Somerton Road in Langport, was originally the A372 for a few years, before that road was diverted away from the town centre.