JPMorgan seeks to turn a lobby into sidewalks at 383 Madison Ave.

JPMorgan’s going to need a bigger sidewalk, it seems.

The Midtown-based bank is seeking a green light from the Department of City Planning to remove walls lining the lobby at its offices at 383 Madison Ave. in order to transform the lobby into an open-air passageway, according to an application filed Thursday.

The bank, which plans to keep No. 383 even after opening its new headquarters later this year at 270 Park Ave. across the street, also wants to carve a new entrance for No. 383 out of empty retail space on the Madison Avenue side of the full-block building.

The L-shaped lobby, which runs along the length of Vanderbilt Avenue between East 46th and East 47th streets and also down the block between East 47th and Madison, is where JPMorgan Chase & Co. employees file into work.

But non-bank pedestrians are also allowed to walk through the area under the terms of a deal cut by No. 383’s developer and previous occupant, the collapsed bank Bear Stearns. It had to create the public right of way in exchange for the city awarding it 286,000 square feet of air rights from nearby Grand Central Terminal. The space also includes a public entrance to a lower level of Grand Central.

Any changes to publicly owned private spaces, or POPS, require Planning Department approval.

JPMorgan says in its filing that opening up the lobby (though preserving columns to hold up the structure) would essentially boost the width of the sidewalk from 4 feet to 19 feet, which will help “address current and anticipated pedestrian circulation patterns” at a corner that could have thousands of JPMorgan employees buzzing around after 270 Park’s activation. The bank employs about 17,500 workers across several New York locations.

But all those workers will need more ways to access 383 Madison, the filing claims, which is why the bank additionally wants to construct a 50-foot-wide midblock entrance on the Madison side where an AT&T store operated years ago. A Charles Tyrwhitt boutique just to the south of it would remain, the plan shows.

Improving flow at No. 383, a 45-story, 936,000-square-foot tower completed in the early 2000s, would also presumably benefit 270 Park, which will have an entrance on Vanderbilt, according to renderings. The 60-story spire, which will stretch across an entire block between Park and Madison, will also offer a Grand Central entrance and feature a 10,000-square-foot public plaza.

According to the proposal, No. 383’s escalators and stairs to Grand Central would not be given the open-air treatment but remain protected behind glass. Also, the opened-up lobby would keep its ceiling, an overhang that would protect pedestrians from the elements, based on the filing.

No cost was provided for the intended renovations, which were designed by the architecture firm Adamson and AAI. Its previous New York projects include 2 World Trade Center, where the firm teamed with Foster + Partners, the architecture practice behind 270 Park.

Foster + Partners has also reportedly been tapped by JPMorgan to revamp the upper stories of No. 383 once its workers decamp to No. 270.

“As one of the largest employers in Manhattan, we are making significant investments in Midtown with our new headquarters and plans to improve our buildings and the surrounding area for our employees, customers, clients and neighbors,” said JPMorgan spokesman Jack Sterne. “We’ll share more details as we go through the process.”