The A470(T) is a major long-distance connective spine road in Wales, running from Cardiff on the south coast to Llandudno on the north coast. It covers 186 miles (299 km) in its entirety, over a zig-zagging route through the country's mountainous central region, including the Brecon Beacons and much of Snowdonia National Park.

Although it remains a primary trunk route throughout its length, and the southernmost 26 miles (42 km), from Cardiff Bay to Merthyr Tydfil, are mainly direct and good quality dual carriageway, the majority of the route from north of Merthyr Tydfil to Llandudno is single carriageway of variable quality (and even in brief instances single track) in order to accommodate the natural and built landscape. It takes in several town centres, right-angle (or tighter) divergent junctions and sharp curves.

The southernmost point of the route is at The Flourish, Cardiff Bay, outside the Wales Millennium Centre. It runs up Lloyd George Avenue (this was previously Collingdon Road, and the A470 previously ran along the parallel Bute Street), and continues along St. Mary Street in central Cardiff. The road then becomes North Road, and after a tidal flow system running to Maindy and then goes over the flyover at the Gabalfa interchange of the A48 and the A469. It becomes an urban dual-carriageway along Manor Way and Northern Avenue, with a 40 mph (64 km/h) speed limit and with many traffic-signalled crossings. It passes without interruption under the M4 at the giant Coryton roundabout. For the next 15 miles (24 km) it is a modern high-speed dual carriageway by-passing Tongwynlais and Castell Coch, Taff's Well, to Pontypridd. Heading north to Abercynon, the road now follows the route of the Taff Vale Railways Llancaiach Branch to Quakers Yard roundabout, where it is joined by the A4059 from Abercynon, Aberdare and Hirwaun ; the A472 from Ystrad Mynach and Pontypool finally the A4054 from Quakers Yard, and Merthyr Tydfil.