It's been a long time since something new was added to the Motorway Database, but this road is well overdue some attention.
Twisting its way up the Taff Valley from the M4 at Cardiff to the northern edge of Merthyr Tydfil, much of this short but hugely important length of the A470 is an urban motorway in all but name. If all you associate with Wales is the M4 and lonely mountain roads it's perhaps time to think again.
If you're new to Roads.org.uk and unfamiliar with the Motorway Database, you might be surprised to find the A470 being added to it. In truth it hasn't been a database of just motorways for years now; anything motorway-like will qualify if it's long and significant enough. The A470 is just the latest in a series of major A-roads to make it in to the listing; there are others on the list that will arrive sooner or later before the listing is considered complete, including the A299 Thanet Way in Kent, the A46 between Warwick and Newark, and (eventually, when it's completed) Wales' own A465 Heads of the Valleys Road.
For now, though, the A470 is the new arrival, and it's quite enough of a road for anyone.
I was intrigued by your article and the comment about the Coryton roundabout. I went to a certain maps website and the aeriial photograph now shows a slip road in the inside of the roundabout westbound down to the A470 to a junction with a set of traffic lights. I think the "urban motorway" just came to a grinding halt with a cheap and cheerful scheme.
Fortunately not as the motorway-like section (whose credentials I would debate today anyway due to some scarily small-dimension junctions) previously ended about 3/4 mile further south at the traffic light junction with Pantmawr Road. It's actually almost more satisfying now as the expressway section begins bang in the middle of M4 J32.