The first convoys delivering large components needed to build a wind farm in Carmarthenshire are expected to start arriving later.
Local businesses along the route, via Pontardawe, are concerned that their trade could be affected.
Lorries will travel twice a day from Swansea docks to the site near Ammanford over the next few weeks.
The Mynydd y Betws is expected to generate enough electricity to power 23,800 homes.
The 15 turbines are being set up near Cwmgors by Siemens for the Irish utilty Electricity Supply Board (ESB).
The lorries under police escort will leave Swansea at 09:00 BST and 13:00 BST.
Lynette Purcell, a Neath Port Talbot councillor, said the convoys will be “mind-bogglingly disruptive” for Pontardawe.
Each turbine delivery will include three blades, two tower sections, one hub and one nacelle.
Lorries will travel from Fabian Way, onto the M4, exiting at junction 42 before travelling along the A4067 and turning onto the A474 and heading through Pontardawe before arriving at the site.
The journey time is expected to take one hour and 15 minutes.
The wind farm, which is not expected to be completed until January or February 2013, lies on the border between Carmarthenshire and Neath Port Talbot.
Plans have focused on minimising disruption whilst passing through Pontardawe and the area near the site entrance on the outskirts of Cwmgors.
Deliveries will avoid peak traffic hours and arrive on site during mid-morning and early afternoon on weekdays only.
In October last year, around 100 people attended a public meeting in Cwmgors over concerns the road would not be able to cope with the large lorries.
Ms Purcell, also a Pontardawe town councillor, said: “The bottom line, is that once these vehicles are moving on that road then everything stops and there’s no alternative route.
“This is a tiny little Welsh village town and it relies on people popping in and out of town. But they won’t be doing any popping out now because they won’t know when the roads will be clear.
“The town relies on this and I’m concerned the impact will be devastating.”