Mayor Bill de Blasio says he wants the MTA to revive plans for a subway line down Utica Avenue, even as the agency wrestles with delays and massive funding shortfalls on other pricey projects. NY1's Jose Martinez filed the following report.

The mayor's got a big idea on transit that goes far beyond riding the subway for photo ops, like extending the number 4 line beyond Eastern Parkway and Utica Avenue in Brooklyn.

"We're obviously an outer-borough city, and yet, there are huge swaths of the outer boroughs that don't get enough service, and this is an example of a line that might make a lot of sense to expand," said Mayor Bill de Blasio.

On Wednesday, as part of his futuristic OneNYC plan, de Blasio said he'll ask the MTA to take a new look at building the Utica Avenue extension.

The need is there. Without a subway line, 15 million people ride the B46 on Utica Avenue each year, the third-busiest bus line in the city. 

"The train holds more people than the buses," said one commuter.

But is the proposal realistic? The MTA is already facing a $15 billion dollar shortfall in its $32 billion dollar plan to maintain and expand the existing system, which is struggling to keep up with surging ridership.

"Now, you have de Blasio wanting Utica Avenue subway to be his signature project. But people are always interested in starting these projects. They're never interested in finishing them," said Nicole Gelinas of the Manhattan Institute for Policy Research.

The Second Avenue Subway was proposed in the 1920s, and the first phase, a three-station spur, still isn't finished. And the East Side Access megaproject bringing the Long Island Rail Road to Grand Central is billions over budget and years behind schedule.

To get a sense of just how tough it is to do subway construction in the city, one need look no further than the one-station extension of the 7 train to 34th Street-Hudson Yards, a project whose opening has been pushed back several times.

But de Blasio isn't the only one dreaming big. City Councilman Ydanis Rodriguez wants the MTA, an agency controlled by the state, to build a new east-west line linking Manhattan and the Bronx.

"Another multi-billion dollar project when the MTA has no money for these existing projects," Gelinas said.

While commuters face the daily reality of overcrowded trains.