Another obstacle is the cost. The new plan puts it at $122 million, nearly as much as the cost of the Community Parks Initiative that Mr. de Blasio announced last week. That $130 million plan calls for rebuilding 35 small, neglected parks in low-income areas across the city.

But while Friends of the High Line raised the money to operate the park that runs through Chelsea, in Manhattan, most of the capital costs were covered by the city. By offering bicycle and pedestrian paths, the QueensWay might be eligible for federal transportation money.

In recent years, the city invested $140 million in the construction of the High Line and far more than that each on Governors Island, Hudson River Park and Brooklyn Bridge Park. “In the grand scheme of things, even if all the money were public,” Mr. Benepe said, “it would be far from the city’s most elaborate or expensive project.”

The Trust for Public Land, which is trying to raise $40 million for the elevated park now under construction in Chicago, known as the 606, has already raised $1.2 million in support of the QueensWay, including $467,000 in state park funds.

The plan has been shown to officials from the city’s parks and transportation departments, as well as City Hall. But the response so far is noncommittal. “We look forward to continuing conversations with stakeholders about the future of this asset,” Wiley Norvell, a spokesman for Mr. de Blasio’s office, said on Monday.