Last week's answer

Question: In 1935, the historic Labor Day Hurricane wiped out huge sections of Henry Flagler’s famous Key West Extension of the Florida East Coast Railway. When the state of Florida stepped in to rebuild the route as the continuous Overseas Highway (US 1), how did road builders rapidly construct miles of highway across open ocean channels without pouring thousands of new concrete piers?

Answer: They paved directly on top of the surviving concrete arch viaducts and converted the old steel railway bridges into two-lane highway decks.

The land used for the railroad was sold to the state, and what is now known as the Overseas Highway was built along the railroad's path, and in some areas built along the surviving portions of the rail. 

Sources: The Center for Land Use Interpretation