Caerphilly County Borough Council (CCBC) has issued an update on the work being carried out at the Pwllypant roundabout.
The roundabout is set to be reduced to a single lane from Monday, July 30, while Heol Pwllypant will become one-way and access from the roundabout blocked.
A spokesman for CCBC said: “Work continues to progress well on the Pwllypant roundabout improvement scheme in Caerphilly.
“Motorists are reminded that the roundabout and its approach from the Llanbradach bypass will be reduced to a single lane from Monday 30th July, following the Big Cheese weekend.
“The single lane arrangements will be in place throughout August to enable the contractor to carry out essential works in the verge and central reservation.”
The merge from two lanes to one will begin at the bottom of the Llanbradach bypass. Traffic from Llanbradach village will join the single lane at the Coed-y-Brain roundabout.
The one-way restriction on Heol Pwllypant are due to essential work being undertaken on the Heol Pwllypant arm of the roundabout.
Traffic will not be able to exit the roundabout onto Heol Pwllypant, but traffic coming down the hill will be able to access the roundabout.
It is estimated that the works will take four to five weeks to complete.
Buses will continue to operate, although routes will be adjusted to take account of the lane closure.