Temporary three-way traffic lights will be in place on the A4061 Rhigos Road at the main site entrance to the Pen y Cymoedd wind farm from Tuesday 10 June.
The reduction from two lanes to one will last for about four weeks.
Following that period, the temporary traffic lights will remain, although two-way traffic will be maintained unless site access is required.
Eryl Roberts, project manager on Pen y Cymoedd, said: “This will allow our plant vehicles to cross the road safely while improvements are made to the eastern main site entrance.
“We have scheduled the deliveries so that both lanes can remain open where possible, so we cause minimal disruption.”
Information provided by Anthony Bullick