Works to repair the Fen Bridge near Crowland are set to begin next week.
The road will be closed during the day, but open in the evenings and at weekends.
There will be temporary traffic lights there at those times.
The improvements are expected to be completed by Friday 13 October, weather-permitting.
During the closures, traffic will be diverted via the B1166, B1040, A16, B1443, A15, B1524, B1166 and vice-versa.