An eight-day repair project on the Kessock Bridge on the A9 at Inverness is due to start on Sunday.
Highland Council and contractor Scotland Transerv have warned travellers and commuters to expect delays to their journeys.
Two extra carriages are to be made available on train services in the Highlands during the work.
Highland Council said the repairs, planned to run until 26 June, were urgent and essential.
To help ease congestion, ScotRail will provide an extra 121 seats on both the 0634 Lairg to Inverness and 1715 Inverness to Ardgay services.
Employers have also been asked to be flexible about workers' commutes.
Both lanes of the northbound carriageway will be closed for the first three days of the project to allow that section of the expansion joint to be dismantled and reassembled.
From 23 June, both lanes of the southbound carriageway will be closed until the evening of 26 June for work on the southbound joint.