Balfour Beatty will start work this week on the Third Don Crossing in Aberdeen.
The firm was selected for the job last month.
Besides construction of the crossing over the Don, the contract includes a smaller bridge across a mill lade, and 2.5km of road, including a stretch of new carriageway linking to the road network north of the river, and the realignment and upgrade of roads to the south.
The crossing itself is a 90m-span structure, using twin open box steel girders, supporting a reinforced concrete deck.
Balfour Beatty is also part of the Connect Roads consortium building the £745M Aberdeen Western Peripheral Route.
The Third Don Crossing is expected to be open to the public by late 2015.