The MTA’s new, $11 billion LIRR train hall under Grand Central Terminal has turned into a gleaming shrine to commuter mayhem, with furious riders left fuming at Jamaica Station on Day 4 of its runs — as largely empty trains rolled into Manhattan.

“It’s a hot mess!” fumed Krista Clancy, 45, who works in Manhattan’s Garment District. “I’ve been commuting for 25 years from Lynbrook to Penn [Station] and I’ve always had an express.

“The past days I’ve been connecting in Jamaica and adding a half-hour to my commute each way. And now look at this! I can’t even get on any of these Penn trains, they’re so packed — and all these Grand Central trains are half empty?” she said.

The infuriating situation is the result of controversial changes to the Long Island Rail Road’s schedule that went into effect Monday to accommodate full-time LIRR service to its new Manhattan terminal, called Grand Central Madison.

The revisions eliminated most trips to Brooklyn’s Atlantic Terminal and diverted trains to Manhattan.

They also forced riders to instead pack into overcrowded trains heading to Manhattan’s Penn Station or Jamaica Station in Queens, where they have to make unscheduled transfers at the far side of its 12 platforms.

Meanwhile, there were rows of empty seats on the LIRR trains heading to Grand Central Madison.

A high school teacher who gave her name as Samantha and said she was heading from New Hyde Park to her job in Brooklyn summed up the scene at Jamaica Station with one word: “Insanity!”

“I’m running from Track 12 to Track 3, then they change it to Track 4? That’s five flights of stairs!” she griped. “I’m now waiting 15 minutes with a lot of people who also work in Brooklyn!

The 38-year-old said she’s seen people running and falling “because they’re really confused.”

“They need to add more trains to Brooklyn or go back to the way it was before,” she said. “I’m late for work this morning and I was supposed to give a test. I’ve been late the last four days because of this.”

Ellen M., a graphic designer from Massapequa, said, “You’d have to be a track star to do this every morning!”

“Last three days: run down a platform, up a flight, across a bridge down another flight, with one minute to spare? I’m 61!” she said. “The first day, I didn’t run and I waited for a train I could actually get in and it added 20 or 30 minutes to my commute, waiting for the connection.

“It’s obvious to me: they need more trains,” she added.

Noor Siddique, 49, of Mineola, said, “I am fed up!”

“Why make all these changes? No connection to Atlantic terminal?” he said. “It can’t continue like this. The MTA needs to review the schedules altogether. Some of this doesn’t make any sense.”

Paul Catalano, vice president of sales for the S.K.I. Beer distribution company in Brooklyn, said there was “too much stuff going on and people are getting thrown off their schedule.”

“It makes me concerned for my daughter who’s going to St John’s [University in Queens],” the Deer Park resident said. “I mean, I can figure this out and I don’t really have to worry about my safety because, you know, I’m a decent-sized guy.
“But I’m worried about my daughter transferring here in Jamaica. I’m worried about security,” he added.
The Post counted nearly 20 MTA staffers in orange vests — including high-level managers — on the Jamaica Station platforms Thursday as they directed riders to their trains.

“It’s pretty stressful on them,” one worker said. “The trains to Brooklyn used to be on Track 3 and now they’re on Track 11 and 12. The Grand Central tracks are 1 and 2, and anytime you change people’s schedule — things they’ve been doing for 10,15 years — you know, it’s tough.

“They get into a certain track — ‘Get off here, go there’ — and that’s all completely changed so, yeah, more than a few are legitimately freaked,” the worker added. “We’re just trying to calm them down, slow them down so no one gets hurt.”

Ridership statistics released Wednesday showed that despite the opening of Grand Central Madison, 71% of riders still opted to go to Penn Station during that day’s morning rush.

During a Thursday afternoon news conference, LIRR interim president Catherine Rinaldi blamed the situation at Jamaica Station on “crowding onto Penn trains.”

“We’ve already started to address that by lengthening some of those trains and we’re going to do a lot more of that next week,” she said at Grand Central Madison, the LIRR’s new Manhattan terminal.

“Beginning next week, some of the problems and issues that we’ve been seeing at Jamaica will be much better.”

Rinaldi also said that “ridership patterns are continuing to emerge.”

“Some trains are heavy one day and not the other,” she said. “There’s still a lot of customers going to Penn and what we want to do is give them a better experience, frankly, than what they’ve had this week by lengthening those trains.”