Brooklyn may get a brand-new 5-mile subway line

New York City's Mayor Bill de Blasio wants to see a new subway line in Brooklyn.

In his outline for his new mobility plan "OneNYC," de Blasio called for a study to investigate the feasibility of a subway line down the Utica Ave corridor of Brooklyn.

The mayor called this part of NYC "one of the densest areas of the city without direct access to the subway," according to transit advocacy blog Second Ave Sagas.

As noted in the New York Times, this isn't the first time the idea of running the subway down Utica Ave has been proposed. It was included in subway expansion plans from 1910s, 1920s, and re-introduced as recently as the 1970s

Though it's not a new idea, director of the Rudin Center for Transportation at New York University Mitchell Moss told The Times that "no one expected" this announcement for the mayor.

It's still unclear how this expansion would take shape - whether it would branch off the 4 train from the Eastern Parkway line; or the A or C trains from the Fulton St line (or another proposal altogether).

Another big question is: Who would pay for this rather large project, when the MTA - who would be responsible for the project - has an awful track record for finishing capital projects on budget? That's not to mention the astronomical $15 billion budget gap in the MTA's funding, which would already likely mean a large cut in MTA's proposed capital improvement projects.

It would also take a big chunk of time.

"It's obviously an idea that will take more than a decade to be carried out," Moss said. "But you have to start with an idea."