Overnight closures on A20 Dover route at Roundhill Viaduct
Work has begun to replace damaged components on the Roundhill Viaduct near Folkestone.
The Dover route has been reduced to one lane since May as engineers waited for a part to be made in Europe.
The Highways Agency said one carriageway at a time would be closed overnight until January while the parts are replaced.
Project leader Arvind Ranpuria said the work had been planned to cause "as little disruption as possible".
The work involves replacing a specialist joint that allows the viaduct to expand and contract when the temperature changes.
Diversions will be in place while the work is carried out.