As the city's population keeps growing, increasingly crowded subway lines are struggling to keep up, and the Bronx borough president is out with a proposal that could put even more strain on the system.

Bedford Park Boulevard is the second stop for Number 4 trains out of Woodlawn, but getting a seat during rush hour is no sure thing.

"It's a lot of people," said one rider.

Now, envision more people if a new neighborhood rises over the Concourse train yard alongside the station. That could become a possibility under a proposal by Bronx Borough President Ruben Diaz, who wants the MTA to consider putting a huge platform over the yard to allow for 2 million square feet of development.

"New real estate, where we can can have commercial, residential, retail," Diaz said.

It would be similar to the neighborhood rising on Manhattan's West Side atop a new platform over the Hudson Yards. That project is not expected to aggravate overcrowding on the 7 line, but Nicole Gelinas of the Manhattan Institute says the Diaz proposal would cause problems for Bronx straphangers.

"Subway ridership over the past 20 years, in the whole city, it's gone up by 41 percent. In the Bronx, it's up by almost 60 percent," Gelinas said. "So you've got more and more people crowding into these trains every day."

Diaz says selling air rights to the Concourse Yard would create a windfall for the MTA, money that could be used to improve service.

Riders say their line is stretched enough.

"Building vertically isn't always the answer. It introduces an influx of folks that will create a lot of congestion," said one rider.

The MTA said it will study Diaz's proposal, which also looked at two other Bronx railyards for possible development.

The plans to build over the Concourse Yard date back to the 1960s, and in 1970, ground was actually broken on what would have been the future home of Bronx Community College. However, that plan was shelved during the city's fiscal crisis in the 1970s.

"This is a way for us to sort of finish what was started here," Diaz said.

Buiding the platform would be costly - according to Diaz, possibly $500 million. Gelinas says that estimate is too low. It is one more issue that would have to be hashed out if a new neighborhood is to rise in the Bronx.