A478 road
The A478 road is a major road in Wales. The route is from its junction with the A487 at Cardigan, Ceredigion, to Tenby, Pembrokeshire. It crosses the Preseli Hills and winds through farmland for almost all of its route. The road just touches the very west of Carmarthenshire.
History
A road between Cardigan and Narberth was recorded between 1536 and 1642. The 1555 Highways Act made parishes responsible for the roads that crossed them. Most were unsuitable for wheeled traffic. Turnpike trusts were set up in the late 18th and early 19th centuries to manage road maintenance; at least part of this road came under the Whitland Trust. However, by the mid-19th century, some trusts were badly managed or abused, exacerbating rural poverty and in part leading to the Rebecca riots in the 1840s, some of the earliest of which were on this road, particularly at Efailwen in the Cilymaenllwyd Community. The trusts were reformed in 1844.The northern two-thirds of the A478 was a drovers' road, used for transporting goods and livestock to and from West Wales and Ireland. In the 18th and 19th centuries, Cardigan was a port, the commercial centre of the region and the most important port in South Wales, exporting fish, agricultural products and raw materials, and involved in emigration. In 1815, it possessed 314 ships totalling, seven times more than Cardiff and three times more than Swansea. It had a thriving shipbuilding industry, with over 200 vessels being built both in Cardigan and downstream in the village of Llandudoch. When Cardigan was connected to the Carmarthen and Cardigan Railway in 1886, the decline of the port was hastened. The river silted up and larger vessels could no longer reach the port, which had largely become inactive by the early part of the 20th century.
Route
Cardigan to Crymych
Starting from the roundabout with the A487 south of Cardigan, the A478 soon crosses the county boundary into Pembrokeshire at Glanpwllafon, where it crosses Afon Piliau, a tributary of the River Teifi. The road passes through Pen-y-bryn in Bridell parish, crossing the River Plysgog, and climbs Rhoshill, crosses the B4332 Eglwyswrw-Cenarth road, then climbs the northern slopes of the eastern end of the Preseli Hills through Blaenffos village, bridging the River Nevern at Riverlea, to Crymych village.Crymych to Narberth
Still at an altitude of over, the A478 passes through Pentre Galar hamlet, crosses the county boundary to Carmarthenshire and passes a viewpoint near the summit of Carn Wen, where it reaches its highest altitude of. The quarrying at Carn Wen is clearly visible from the road; quarrying was active in 2025.Passing through Glandy Cross and Efailwen the A478 crosses the county boundary back into Pembrokeshire, passing through Llandissilio to the railway station at Clunderwen. The A478 then crosses the A40 trunk road between Llanddewi Velfrey and Penblewin, to the west of St Clears, at the Penblewin roundabout and passes through Narberth town centre where it meets the B4314.