|Location Map ( geo)|
|To:||Tredegar Junction, Nant-y-bwch (SO131106)|
|Distance:||11.2 miles (18 km)|
|Meets:||A472, B4251, B4254, B4511, B4256, A4047, A465|
|Former Number(s):||B4251, A465|
|Old route now:||A467, B4251|
|Route outline (key)|
The A4048 runs up the Sirhowy Valley from Pontllanfraith to the A465 Heads of the Valleys Road above Tredegar.
The road starts on the A472 at the eastern end of Pontllanfraith. From here it heads generally northwestward, bypassing the town before crossing the Sirhowy via the Chartist Bridge and turning right to join the road's original route northward from Blackwood to Tredegar. It continues upstream, a winding S2 road which runs through a few villages and then passes to the east of Tredegar town centre.
At the northern end of Tredegar it meets the A4047 – which from 1922 until construction of the present Heads of the Valleys Road had been a section of the A465 – coming in from the right. This was the A4048's original terminus; today, however, it continues for a further 1.3 km to meet the modern course of the A465 at Tredegar Junction, Nant-y-bwch, currently (2014) under extensive reconstruction as part of the Heads of the Valleys dualling project. This final stretch of the A4048 largely parallels another section of the original A465, though the modern route has been displaced slightly northward to take advantage of the alignment of a dismantled railway line.
The southern end of the A4048 today is not far from where it had been in 1922, although shifted a kilometre or so east-north-eastwards to the start of the Pontllanfraith bypass, opened in 2005. Earlier, however, the A4048 had been extended in the late 1920s to start rather further south, on the A467, taking over the route of the B4251, which ran from the confluence of the Sirhowy and Ebbw rivers at Cross Keys up the lower Sirhowy Valley as far as Pontllanfraith. With the opening of the bypass, this section reverted to its original classification and is now the B4251 once again (or, more precisely, the southern part of that road's since-extended length).