The A479 originally ran through Builth Wells to Rhayader. This part of the road is now the A470.[5][6] A short section of road near Llyswen was realigned in 1995.[7]
A bypass of Talgarth and Bronllys began construction in 2006. Part of the Talgarth bypass runs on the former Mid-Wales Railway. Because this part of the road runs through the Brecon Beacons, additional treatment was needed to minimise disruption with the nearby countryside. This included a specific alignment of the highway, and replanting of hedgerows to fit in with the existing parts of the road. The bypass opened in 2009.[2]
Traffic
In 2005, the A479 was listed as one of the most dangerous roads in Wales in an AA Motorway Trust report.[8] In 2013, another report suggested the same.[9]
The section of the A479 between Pengenffordd and Talgarth has had regular issues with subsidence. A section south of Talgarth was closed in March 2016.[10] In February 2017, the road was closed for an extended period in order to lay new foundation work.[11] In February 2020, a section of the road near Talgarth was closed following a collapse during Storm Dennis. The damage affected the surface and foundation of the road, resulting it being closed until November.[12][13]