The road measures 5.54 miles long and would take a car obeying speed limits 9 minutes to travel its length.
The A4138 is a A Road and is located in the Zone 4 Highways Region.
This is a true long-distance route, journeying through numerous towns like LLANELLI, Dafen, Bryn, Llangennech, and Pontarddulais.
The road connects Dyfed and West Glamorgan.