The link road into Llanelli from Trostre Roundabout to Farm Foods will be closed for five days in March for tree felling work.
Commuters are advised to plan an alternative route in advance for the week beginning Monday, March 16.
The closure involves about three-quarters of a mile of tree-lined carriageway.
Carmarthenshire County Council executive board member for engineering and transport services , Cllr Colin Evans, said: “There were issues last year when high winds felled trees on this avenue causing major disruption to traffic while emergency removal work was carried out.
“To prevent similar disruptions there is a need to thin and remove older trees with preventive maintenance to make sure that future storms do not cause further disruptions.”
The alternative route for north-west bound traffic will be to travel in a northerly direction along the A4138 to its junction with Glyncoed Terrace. At the junction, turn left and continue in a north-westerly direction along Glyncoed Terrace, Capel Isaf Road and Frondeg Terrace to return to a point north-west of the closure. Vice versa for south-east bound traffic. No access will be available.
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