New York City officials approved the plan Wednesday to build a new, 65-story skyscraper in Manhattan after the developer agreed to make sweeping upgrades to nearby Grand Central Terminal that would allow more rush-hour trains on the subway’s busiest lines.

City Council members unanimously approved a change to zoning law that will allow One Vanderbilt to rise alongside the historic transit hub. In exchange for getting more square footage, SL Green Realty Corp. will invest nearly $220 million in critical improvements to Grand Central, allowing more trains to run during the rush hour on the jammed 4-5-6 lines, which carry more people per day than the entire transit systems of Chicago or Washington.

“This is the first time we've seen vast private investment to improve mass-transit access," said Mitchell Moss, a professor of urban planning at New York University.

The partnership could set an example for future deals, allowing the debt-riddled Metropolitan Transportation Authority to offload the cost of improving its ancient infrastructure onto private developers. And it will transform the stodgy East Midtown area, where the average building is 75 years old and saddled with outdated structural features such as interior columns and low ceilings.

The building is expected to house about 8,000 workers when fully occupied. It will join a parade of new skyscrapers that will soon soar above Midtown Manhattan.

The tower’s new transit hall would funnel workers directly into Grand Central and also provide a crucial direct link from commuter trains to the subway system for the MTA’s East Side Access project, which will bring 65,000 Long Island Rail Road commuters directly into the terminal when it opens in about seven years.

The most important work will happen on the 4-5-6 platform, one of the most notoriously overcrowded waiting areas in the subway system. During rush hour, commuters often have to watch several trains pass before they are able to squeeze onto one. The main problem is lack of space on the platform itself, which is dominated by numerous thick columns that take up unnecessary space, transit officials say.

"This is the bottleneck to the subway line," Edith Hsu-Chen, director of the Manhattan office of the city's department of planning, told city council members during a hearing last month. "Improvements made to this station would affect the entire line and commuters in the whole city."

SL Green will strip the columns down to the bare bones — slimming them down by about a foot each — and narrow the stairwell to create about two and a half feet of extra space on the platform. That may not sound like much, but on a crowded platform, it could make a world of difference: one more train could run per hour during rush hour, according to MTA estimates.

"At rush hour, people congregate around these columns. People can't get off the train," said Robert Schiffer, managing director at SL Green. "The idea is to diffuse people."

All improvements will be complete by 2020 or 2021, about two or three years before the East Side Access project will be finished, Schiffer said.

The Associated Press contributed to this report