Queens has the highest retail vacancy rate in New York City — at 13.7 percent, it is nearly double the rate that Manhattan had in the second quarter of this year. But if there’s one spot where empty storefronts are a rare commodity, it is on Roosevelt Avenue, between roughly 72nd Street and 84th Street, a bustling commercial district on the edge of Jackson Heights.

On the travails of another bustling commercial district in Queens.

Bustling, except for two commercial spaces at the Roosevelt Avenue public transportation hub on 74th Street, which just happens to house the fifth-busiest subway station in the city. The spaces have never been occupied.

Miguel E. Silva, a real estate broker at Ocean Y. Realty, which overlooks the empty stores, called the spaces “the filet mignon of Roosevelt Avenue” because of the hundreds of thousands of potential customers who walk past them every week. Daniel Dromm, the local city councilman, described the spaces as “the biggest impediment to economic development in the community.”

To the area’s residents and merchants, the spaces are sort of a mystery. “I think it’s storage,” speculated Marta Velásquez, a Mexican immigrant who was selling churros outside one of them the other day. Juan Castillo, a street bookseller who is from Ecuador, shrugged his shoulders and said, “They seem abandoned to me.”

The spaces are among 14 stores built when the 74th Street station was renovated — an $18 million project that was completed in 2005. Eleven are leased, all of them in the station’s mezzanine. (A 12th spot on the mezzanine is also vacant.) But getting businesses to open in the street-level spaces has proven to be particularly challenging — for potential tenants and for the landlord, the Metropolitan Transportation Authority.

In one of the stores — a space measuring roughly 4,000 square feet and spreading across two floors along Roosevelt Avenue, between 74th and 75th Streets — bags of insulation are piled up near a roll of orange mesh fence the transportation authority uses to block access to parts of a station that are undergoing work. Outside, the paint on the wood boards that encase it is peeling and the sidewalk is covered in bird droppings.

Of the signs advertising that the space is available, one faces an access road used by buses and is hardly visible to pedestrians. The other is not hard to spot, but the phone number for the authority’s real estate office is obscured by a sticker publicizing legal services: divorces for $299, bankruptcy proceedings for $399.

The transportation authority first requested proposals for the space on Roosevelt Avenue in 2006 and got back a single response, from a Korean businessman who wanted to open a bakery, agency officials said. The businessman signed a 10-year lease in 2007, paid a $40,000 deposit and then an additional $75,000 in 2008, when he told the agency that he needed more time because of problems with the architect he had hired for the project.

The second space — a triangular store of about 200 square feet — cannot accommodate a ventilation system because of its odd configuration, making it impossible to house a pizza parlor that someone had intended to open there, the officials said.

No lease has ever been signed for the smaller space, and the lease for the larger one was not voided until September 2008, almost two years after it was signed. Though the Korean businessman forfeited his deposits, he never paid any rent on the space.

“That’s the ultimate absurdity of this whole deal,” Mr. Dromm said.

Mr. Dromm is particularly troubled by the impression that the shuttered stores might leave on visitors. The subway station is a gateway to the neighborhood and “it’s not a good thing if the first thing you see is boarded-up commercial space,” he said.

A spokesman for the authority, Kevin B. Ortiz, said that for the most part, the agency had been “pretty successful” in filling the retail spaces at the station, but would hire an outside broker to market the street-level spaces.

For now, the agency is working to do some of the finishing work that tenants are often required to complete, as retail spaces rented by the transportation authority are delivered raw. It is all in a bid to make them more attractive.