The final phase of resurfacing work on the Cleddau Bridge started this week.
Two-thirds of the work was completed last year before contractors pulled off site for the winter months.
It is envisaged that this last phase will be completed by the beginning of July.
The two lanes currently used by motorists will be kept open during the work, which is being carried out by the contractor Alun Griffiths Limited.
"This work will be of major benefit to the Cleddau Bridge," said Clr. Brian Hall, cabinet member for transportation and environment. "The finished carriageway will have a better ride quality and will be three lanes wide, with steel barriers to separate the road from the footways or cycleways."
The work includes extensive repairs of the steel bridge deck, re-waterproofing and the refurbishment of the main movement joint. The final phase will also involve the renovation and enhancement of the toll booth area.
"A new major feature will be the erection of a landmark canopy structure over the booths," said Clr. Hall. "The aim of this is to highlight the gateway to the bridge, and to provide extra weather protection to the toll collectors.
"Other work includes replacing the existing toll booths, replacing and upgrading signage, and providing a dedicated parking area and safe crossing to the toll booth office for south-bound drivers."