|Location Map ( geo)|
|Distance:||14.7 miles (23.7 km)|
|Meets:||A465, B4242, A4221, A4230|
|Route outline (key)|
The A4109 loops off the A465 to serve the Dulais Valley. Unclassified in 1922, the road gained its number as a part of the Inter-Valley Road Scheme, a major road-building project that took place between 1925 and 1929, although for a few years in the 1920s the route so numbered ran only from a point immediately north of Crynant down to Aberdulais – as the continuation of the B4285 from Banwen.
The route starts today at a trumpet interchange on the A465 dual carriageway by Glynneath. It crosses the River Neath and then the B4242 (former A465) at traffic lights in the centre of the village. The road quickly bends to the right to begin climbing out of the valley, heading at first northeastward but gradually curving round to the left until, by the time it reaches its summit near Banwen, we are heading west by northwest across the moorland above the small Afon Pyrddin.
Immediately after intersecting a minor road which was once part of Sarn Helen – the Roman way from Neath to Brecon – the A4109 TOTSOs left at a fork in the road (the main road right and ahead is the A4221, a much later development dating from the 1970s and leading into the Swansea Valley). Our road passes under a dismantled railway line and soon we start descending the Dulais Valley through Onllwyn.
After passing a coal washery on the right and a small cemetery on the left we run alongside a freight-only railway line into Seven Sisters, where the road takes a circuitous route, involving a number of 90-degree corners, through the village streets. After bridging the railway line, the road doubles back on itself but soon we are heading southwestward down the valley once again. The road is now built-up for a couple of miles but we eventually enter valley-bottom terrain with woods and pastures quite different from the moorland we were crossing earlier.
The next village is Crynant, at the entry to which we pass a right turn into a road leading across Rhos Common to Ystradgynlais. Somewhat strangely, this important road – the only one below Onllwyn to connect the Dulais and Swansea Valleys, and part of the Swansea to Brecon long-distance bus route – remains unclassified.
On leaving Crynant we cross the railway line once more (this time via an underbridge), pass the Cefn Coed Colliery Museum, and continue to follow the Dulais downstream for another couple of miles to Aberdulais, where we meet the B4242 (former A465) again. The A4109 once ended at this point but our route now has priority through the junction and we continue along the old route of the A465, crossing the River Dulais by the Aberdulais Falls National Trust property, before we reach a roundabout and grade-separated junction with the modern A465, as well as the A4230, which takes onward local traffic into Neath via Cadoxton.
The 4.5 mile road from Glynneath to Banwen was opened on 4 November 1929. Contractor was John McColville, Abergavenny.