PRELIMINARY works will start on October 16 as part of the Wind Street / Tirydail Lane Junction Improvement in Ammanford.
The works will be carried out overnight from 7pm over five nights in order to minimise disruption to the public.
The traffic signals at the junction will be switched off whilst the works are underway and traffic will be controlled manually.
The proposals include a new roundabout at the Wind Street / Tirydail Lane Junction (to replace the traffic signals) and the widening of William Walker Way from the new roundabout to the Carregamman Lane car park roundabout.
The scheme will help to ease traffic congestion at the Wind Street / Tirydail Lane junction, particularly during peak times.
Detailed designs are being prepared on the proposals and will be finalised following the investigation works being carried out next week.
This widening of William Walker Way is most likely to be the first phase of the construction work and is scheduled to start in early 2018 with a likely construction period of eight or nine months.
Executive Board Member for the Environment Cllr Hazel Evans said: “Traffic congestion is a major issue at this location especially at peak times. The proposed scheme will help to relieve congestion and is a key element of the Ammanford regeneration plans.
“As Wind Street is a trunk road, these works will be carried out during non-peak hours and every effort will be made to minimise disruption as much as possible.”
The council has received a grant of £865,000 from the Welsh Government’s Local Transport Fund 2017/18 to progress the scheme.