The first day of Amtrak’s summer track work program at Penn Station appeared to buck expectations Monday, even for subway riders at Atlantic Terminal.

No. 2, 3, 4 and 5 trains ran regularly from Atlantic Avenue, with many arriving about four minutes apart, for the first day of rerouting LIRR trains from Penn Station. Anticipating an influx of additional riders, an MTA spokesman said the agency also added two No. 7 trains.

Diane Ralph, a paralegal from West Hempstead, said she avoided the No. 7 train, opting to take the Glen Cove ferry instead.

“Even though the No. 7 is more convenient, the squeeze is going to be not good,” Ralph said. “How often do you get to take the ferry to work? The weather is nice. We’ll see how it goes.”

Monday kicked off the start of an eight-week track work program at Penn Station. Amid increasing derailments and delays due to aging infrastructure, Amtrak announced earlier this summer it would need to shut down several tracks at the station in order to make critical safety improvements.

Ahead of the track work, transit advocates voiced concerns of overcrowding at subway stations where the MTA was offering to cross honor LIRR tickets as part of its mitigation program.

While some straphangers noted that subway platforms and stations felt a bit more crowded than usual, none seemed too phased by the additional commuters.

At Atlantic Avenue, MTA workers ushered LIRR riders through the open gates, asking them to hold up their tickets. The MTA is cross-honoring LIRR tickets at the Brooklyn station.

“It can get this crowded,” said Flatbush resident Dane Lay, 30. He waited for one No. 4 train to pass before hopping on. “I was like ‘I’m not going to bother with that one.’

“I just have to deal with it,” Lay said. “I don’t have any other way to get to work.”

Woodlawn resident Olga Figueroa, 55, took the No. 4 train in Brooklyn for an appointment, and said the line is always crowded.

“It’s a little messy,” she said, adding she hopes kids being out of school for the summer will help the overcrowding — and the pushing that comes with it. “You’ve got to accept it, you’re on a crowded train.”

Speaking Monday morning, MTA chairman Joseph Lhota said, so far, “everything has been on time” and “working according to plan.”

Nick Sifuentes, the deputy director of the Riders Alliance, said Monday morning’s commute was largely fine, but he’s more concerned about what happens when everything doesn’t go according to plan.

“What’s going to happen when we have another meltdown on the system?” Sifuentes said. “With a subway system that’s already overcrowded how is it going to handle riders who are already displaced?”

Sifuentes said he thinks there will be additional riders at Atlantic Avenue as the days and weeks go on, but credited the MTA with good preparation for the disruptive track work.

With Chau Lam