Construction costs for the 1,776-foot tower have been pegged at $2.478 billion, up from the $2.2 billion estimate for steel, concrete, glass and labor projected last spring.

But the latest tally included in the Port Authority’s capital budget includes an additional $507 million for “nonconstruction” costs that include security at the site, integrity monitors to keep an eye on contractors, the cost of selling bonds to finance the project, marketing the office space and fitting it out for tenants, The Post has learned.

Adding all the costs, the price tag for the Freedom Tower budgeted by the bistate agency is $3 billion — making it not just the tallest building in the city, but also the most expensive.

The first weekend there will be no trains between Times Square and Queensboro Plaza. After that, there will be no trains from 74th St./Broadway in Queens to Times Square.

TA spokesman Paul Fleuranges said the work is part of the agency’s long-term plan for maintenance and upgrades, including replacing tracks, signals and rickety trains.

“Without these investments, the system would not be near as reliable as it is today,” he said. “With this investment comes a price, and that is disruptions in normal service. For that we apologize.”

Michael Murphy, 28, a public relations executive from Queens, couldn’t believe that TA would schedule such work for St. Patrick’s Day, which falls on a Saturday this year, when so many New Yorkers will be heading to the parade.

“We go through here every day, and everyone still looks at us like ‘What the heck is this?'” said Tom Materka, a rail freight engineer, as the train approached the Hicksville station, one of the Long Island Rail Road’s busiest commuter stops, one recent afternoon. “People are always shocked to see a freight train coming through here.”

Mr. Materka, 30, an engineer for the New York & Atlantic Railway, one of the few remaining short-line rail freight companies in the region, was running two screaming 120-ton diesel locomotives towing a string of sooty boxcars from Queens out to eastern Long Island. Well-dressed commuters looked up from their newspapers and coffee and stared as the smoky train roared by and transformed the suburban station into Tumbleweed Junction.

The line uses obscure rail tracks in Queens and Brooklyn and tracks of the Long Island Rail Road in Nassau and Suffolk Counties.

Since freight trains are far outnumbered by commuter trains, few people glimpse the bulky, graffiti-covered boxcars as they lumber past the sleek silver commuter cars rushing passengers to or from Pennsylvania Station.

[Transportation Alternatives executive director] Mr. [Paul Steely] White represents the left flank, then, of a set of strange bedfellows. Founded by radical bicyclists in the 1970’s, Transportation Alternatives comes across as a sort of alterna-elite group of forward-thinking urban planners.

About half of its 5,500 members are from Manhattan and brownstone Brooklyn, and its 18 full- and part-time employees are generally white, well-educated twentysomethings who ride their bikes to work. Many of its largest donors are Wall Street types, and its largest individual funder is Mark Gorton, the high-tech entrepreneur who founded LimeWire. To them, Mr. White says, “Biking is the new golf.”

But T.A., as it’s called, has long tried to project itself as a generally pro-person, anti-traffic group. The city Department of Transportation ended up copying Safe Routes to Schools, a program established by Mr. White’s predecessor, John Kaehny, which seeks improvements to streets near schools. A similar program, Safe Routes for Seniors, is next in line for adoption, Mr. White hopes.

And the group regularly submits suggestions for traffic improvements throughout the city, sponsors bike rides, and gives away helmets in poor neighborhoods.

Major work will occur between East 96th and East 92nd streets, where a hole will be dug to get the tunnel-boring machine underground. Some utility infrastructure will also be relocated.

The first phase of the $3.83 billion project to create a new Lexington Avenue line from 96th Street to 63rd Street will also come in under budget.

The MTA budgeted $350 million for initial tunneling, but the agency’s contractor said it can do it for $337 million.