ROME — When the Morandi Bridge, a vital east-west transportation artery in the heart of Genoa, collapsed on Aug. 14, 2018, killing 43 people, there was little reason to think that its replacement would be in the final phases of construction less than two years later.

Public works projects in Italy are not known for efficiency, even under the best of circumstances, and the months after the accident were marked by a series of obstacles: political turmoil that led to a change of government, judicial investigations into the cause of the collapse, and a debate over whether the privatization of Italy’s roadways and other infrastructure had put people at risk.

And that was before the coronavirus struck.

Yet on Tuesday, the last section of the deck that forms the main structure of the new bridge was hoisted into place, completing a 3,500-foot-long spine that remains to be covered in concrete and then finished with a layer of asphalt.