The A4138 is a main road in Carmarthenshire

Carmarthenshire

Carmarthenshire is a unitary authority in the south west of Wales and one of thirteen historic counties. It is the 3rd largest in Wales. Its three largest towns are Llanelli, Carmarthen and Ammanford...

, Wales

Wales

Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...

, connecting Pontarddulais

Pontarddulais

Pontarddulais is a community and town in the City and County of Swansea, Wales. It is situated north west of Swansea city centre. It falls within the Pontarddulais ward.-Overview:...

 with Llanelli

Llanelli

Llanelli , the largest town in both the county of Carmarthenshire and the preserved county of Dyfed , Wales, sits on the Loughor estuary on the West Wales coast, approximately west-north-west of Swansea and south-east of the county town, Carmarthen. The town is famous for its proud rugby...

. Running in a north-east to south-west direction, the road connects with M4 Junction 48.

North-east of the motorway, the road is classified as the , south-west of the motorway, the road is classified as the .

Settlements served by the road include:

• Pontarddulais
  Pontarddulais
  Pontarddulais is a community and town in the City and County of Swansea, Wales. It is situated north west of Swansea city centre. It falls within the Pontarddulais ward.-Overview:...
  
  
• Hendy
  Hendy
  Yr Hendy is a village in the community of Llanedi, Carmarthenshire, Wales, situated on the border between Carmarthenshire and Swansea. Yr Hendy lies on the Afon Gwili just across the River Loughor from the town of Pontarddulais and, together with Fforest to its north, forms part of the continuous...
  
  
• Dafen
  Dafen
  Dafen is a village situated east of Llanelli in Carmarthenshire, Wales, part of the Llanelli Rural community. Dafen borders the villages of Felinfoel, Llangennech, Bryn and Pemberton....
  
  
• Penceiliogi
• Llanelli
  Llanelli
  Llanelli , the largest town in both the county of Carmarthenshire and the preserved county of Dyfed , Wales, sits on the Loughor estuary on the West Wales coast, approximately west-north-west of Swansea and south-east of the county town, Carmarthen. The town is famous for its proud rugby...