Work on improving the M4 Motorway junction with the A4138 which links Pontarddulais and Llanelli is to start on Monday 12 April.
Carmarthenshire Council say they anticipate the work will take 9-12 months to complete.
The carriageway will be widened to help reduce queuing traffic joining and leaving the M4 along the A4138 during peak times. The footway will also be upgraded to a shared use path for pedestrians and cyclists.
The Welsh Government has committed funding of £2.9m to address issues at the junction.
Junction 48 at Hendy is the main interchange for traffic accessing Llanelli and Pontarddulais from the M4. It currently sees significant congestion during peak periods, with limited to non-existent provision for cyclists passing through.
Proposals involve widening the carriageway of the A4138 to reduce congestion as people join and leave the motorway, as well as new traffic signals to improve traffic flow and safety.
A shared use pedestrian and cyclist facility, linking with the route recently constructed between the A4138 and Llanelli will also be created, providing a continuous link between Hendy and Llangennech.
In a facebook post, the council said: “We thank you in advance for your cooperation and patience whilst we work to carry out these improvements. There will inevitably be some disruption but we will try to keep this to a minimum.”
(Lead image: Google Maps)