In New York, the idea of replacing the Brooklyn-Queens Expressway with a tunnel has been debated over the years and dismissed largely because of the enormous price tag — money that officials and transportation advocates say could instead be spent on fixing the subway and other mass transit.

Now Arup, a global engineering firm hired by the City Council to look at alternatives, said the tunnel option should be reconsidered because of advancements in technology like digging and ventilation.

Mayor Bill de Blasio and city transportation officials would have to embrace any plan for the highway, and the city has already reviewed — and rejected — the idea of a tunnel because of financial and logistical challenges, including digging in areas with subway lines and water tunnels and below residential neighborhoods with historic buildings.

Officials at City Hall said they would review the Council’s report.

A 57-foot-wide tunnel could run underground from the Gowanus Canal to the Brooklyn Navy Yard, according to the 67-page report. The triple-cantilever structure that is part of the B.Q.E. would be torn down. The famed Brooklyn Heights Promenade that sits above it would be preserved. A four-lane boulevard would run from Atlantic Avenue to the Columbia Heights Bridge.

But Sam Schwartz, a transportation consultant, said that a tunnel might not be a realistic option — the existing highway is deteriorating and could be unsafe to traffic within five years. A tunnel could take many years.

“It would set back the process,” Mr. Schwartz said. “Here we have a patient — the B.Q.E. — in the intensive care unit. It cannot wait 10 years for a tunnel to be built.”