|To:||Brecon Beacons (SN989182)|
|Length:||21.2 miles (34.1 km)|
|Meets:||A470, A472, B4275, A4233, B4276, A465, A4061, A470|
|Old route now:||B4275|
|Route outline (key)|
The A4059 could be described as a "long way round" road, given it starts and finishes on the A470 (which is only about five miles shorter). It can also be split into two quite different halves, which can be explained by the road's history.
The first half is urban in nature. It starts on the A470 near Abercynon at what is the first flat roundabout for that road north of Cardiff. It heads west, following the various former mining communities along the Cynon valley through Mountain Ash and Aberdare, although most of this now runs on a new relief road avoiding the older built-up streets. The old road is now the B4275 but only west of Mountain Ash; east of there the A4059 still follows its original route.
After rejoining its old route in time to go through Penywaun, the road meets the A465 and multiplexes along it between adjacent roundabouts to bypass Hirwaun. The road regains its number to go through Penderyn then changes character completely to a great rural drive over heathland with the Brecon Beacons in full view. It winds back down to the A470, which it meets again at the Beacons Reservoir.
The A4059 did not bypass Hirwaun until the mid 1990s, about 30 years after the A465 did.