Bridge Valley Road will be closed entirely over the weekend, while temporary lights will be installed on the Portway to allow two-way traffic through a single lane.
The closures are vital so the council team can secure a large boulder, which has fallen partway down the cliff face over the junction.
The boulder will be lowered safely while the area is surveyed to determine what further steps are required. In the short term, further closures of Bridge Valley Road may be necessary to remove the boulder and clear the rock trap at the foot of the cliff.
Cllr Kye Dudd, Cabinet Member for Transport at Bristol City Council, said:
“We apologise for the inconvenience caused by these road closures, as we know how frustrating it can be when your journey is disrupted.
“These works are absolutely necessary and must take place soon due to the position of the boulder, and the growing risk to motorists and pedestrians if it were left unattended as we head into winter.
“Council teams will be working as quickly as they can to complete these emergency works and we will open these roads again as soon as possible.”
Visit Travelwest's Twitter account for updates and please allow extra time for journeys. Local businesses will remain open during this period.