Essential work will be carried out at Taw Bridge in Barnstaple, starting from next week.
The existing parapets are being replaced, initially on the west side of the bridge from Monday (2 December).
The footpath on this side of the bridge will be closed and pedestrians will be diverted via Barnstaple Long Bridge and along the South West Coast Path.
A 20mph speed restriction will be in place while work is being undertaken in order to protect the public and site staff. However, the bridge will remain fully open to traffic.
This first phase of work is expected to be completed before Christmas and no restrictions will be in place during the holidays once this section is complete.
In early January, work will get underway to replace the parapet on the east side of the bridge. A 20mph speed restriction will again be in place, and lanes will be narrowed on both carriageways.
During this second phase, vehicles will have full access across the bridge and the footpath on the west side will be open.
The scheme is expected to be completed by the end of January.