New year, new commute.

New Yorkers on Sunday pumped their fists in triumph as they stepped onto the Second Avenue subway platforms for the first time. On Tuesday morning, they were rubbing their bleary eyes as the three-station expansion became a normalized part of their rush-hour journey.

Early risers on the Upper East Side were optimistic that the first phase of the project, nearly 96 years in the making, would have a huge impact on their commutes.

“This is life-changing for me,” said Sara Hecht, 25, who moved right above the 86th Street station in September. She said she would usually attempt to squeeze into a train on Lexington Avenue, but often resorted to walking about two miles to her sales job to avoid the crush of commuters.

Hecht half-joked that transit inaccessibility in her Yorkville neighborhood had a detrimental impact on her life.

“I never got to work on time. I never got to the gym on time — my workouts were shorter; I was gaining weight,” she laughed.

Depending on where you live, the optimism was tempered for the long-awaited, $4.5 billion project. Andrew Haynes, 32, who has lived a few blocks from the 86th Street station for five years now, was torn between whether a No. 4 or 5 train commute would be better than Second Avenue. Haynes said he would be tracking his trip to work to see if it is faster than the notoriously crowded Lexington Avenue line, which carries about 1.3 million riders each day.

“If it turns out to be about the same time, I’d still come here to a clean platform and a less hectic train,” said Haynes, of Second Avenue. “I think the wait might be longer, but I’ll be watching closely.”

So is the MTA. Staff were counting entries with manual clickers, monitoring train headways and passenger buildups in stations. The agency will be keeping an eye on demand for the first few weeks, according to Ronnie Hakim, president of New York City Transit.

“We have estimates; we have models, but there’s nothing like seeing it for yourself,” said Hakim, who visited the 86th Street station during the morning rush. “We’ll be out for weeks, frankly, in order to monitor what the service needs are and make adjustments as necessary.”

The agency anticipates about 200,000 daily riders to use new stations at 72nd, 86th and 96th streets. Rush hour on day one didn’t go without a hitch. There were Q train delays in both directions due to switch problems at Prospect Park, according to the MTA.

Some things a new year can’t change. But, overall, the mood was positive for riders who had the opportunity to finally avoid Lexington Avenue.

“It’s a quality of life improvement … Folks who live on the east side of the Upper East Side had previously had to walk to 86th Street and Lexington and take the IRT down,” said Hakim. “Frankly, we know how crowded the Lexington line is. So this provides a relief valve of huge impact.”