Motorists are being warned to expect some travel disruption as £13m works to improve a regular congestion hotspot on the M4 starts this week.
The 16-month project aims to reconfigure and “increase capacity” of junction 28 of the M4 near Tredegar Park, Newport.
The adjacent roundabouts at Bassaleg on Forge Road and Pont Ebbw at Tredegar Park’s entrance will also be upgraded.
The work, starting Tuesday, aims to “reduce delays” in the area.
But, there are fears the project, which is expected to be completed by July 2018, could increase congestion while the construction work is taking place.
A spokesman for the Welsh Government says lanes will be narrower and off-peak lane closures will be put in place.
Permanent traffic lights will also be installed at the neighbouring roundabouts which will have “smart signalling” so the they will “be synced to ensure the smoothest and quickest traffic flow”.
Two lanes will be built through the middle of junction 28 to allow traffic from the eastbound carriageway of the M4 to access the Southern Distributor Road (SDR) around Newport without going around the roundabout.
Improvements will also be made on the Pont Ebbw roundabout to ease traffic flow on the SDR.
A spokesman for the Welsh Government told BBC Wales: “Existing junction traffic capacity will be maintained during peak hours – prior to 09:30 GMT and after 15:30 during weekdays – throughout the construction phase, albeit the lanes will be narrower in order to provide working room.
“Off-peak lane closures will be utilised between 09:30 and 15:30 to facilitate the works when traffic flows are lighter.”