It was a New Year’s Day to mark a new era for the MTA and residents of the Upper East Side, who had waited decades for the Second Avenue subway line to be completed.

Cheers went up among the riders who packed a southbound Q train from 96th Street. They were joined by Gov. Andrew M. Cuomo and MTA Chairman Thomas Prendergast.

Cuomo, over the train's loudspeaker system, wished those aboard a happy new year. 

"We deserve it, we need it, and I believe we're going to have it in 2017," he said.

Some of his message was garbled by the system. Later, when the new Q train reached the Lexington-63rd Street station, there was another stereotypical snag. The train sat for several minutes in the station and a conductor's voice over the loudspeaker explained it was "experiencing signal problems."

Riders just laughed. It seemed their mood at the arrival of this historic moment couldn't be dampened. The train eventually continued on toward Brooklyn.

"It's very clean," Monica Elvira, 40, of the Upper East Side, marveled of the train and new stations. In addition to carrying a maraca, she wore a headband reading, "2017."

"This is a great way to start the new year," she said.

Meanwhile in midtown, the first northbound Q train departed from 57th Street-Seventh Avenue station at 12:01 p.m.

Eager riders gathered at the station hours in advance to ensure they had a seat for the uptown trip, and hooted and gawked as the train rolled through the three new stations at 72nd, 86th and 96th streets.

"I'm thrilled. This is going to make a huge difference in my life," said Jaclyn Kelly, 38, who lives on 73rd Street between First and Second avenues. "I spent time Googling all the places I can now go to by subway — it's exciting."

The cars were filled with plenty of commuters who have taken inaugural subway rides before. Joe Caronetti, 68, from Norwood, the Bronx, said he's been to about five similar events in his lifetime, including the Hudson Yards extension and the opening of the Whitehall South Ferry terminal. 

"With all the cutbacks and fare increases, we need this," Caronetti said, who noted that he was disappointed the line wouldn't travel all the way into his home borough, as originally conceived. "It's nice to see something given back." 

Charlie Pellet, a radio anchor and voice of the MTA’s announcement system, merrily greeted riders who requested him to repeat commands like “stand clear of the closing doors, please.” He even recorded a new voicemail message for one fan.

Juan Amador was the operator for the first northbound Q train from 57th Street. Once Amador reached his 96th Street terminus, he posed for photos with wide-eyed children.

"We're making history, it feels great," said Amador, 56, of Elmhurst, Queens, who has spent five years with the agency as an operator. "It's been long overdue, but we did it for New York City."

The MTA anticipates the new stations will serve a total of 200,000 riders per day. Though the $4.5 billion first phase delivered only about a quarter of the entire length of the proposed Second Avenue line — 2 miles of 8.5 miles of track — experts and advocates anticipate an appreciable impact throughout the subway network. Commuters nearby will now have a direct connection to several transit hubs, including Times Square, Herald Square and 14th Street.

"We’re all looking forward to this. It’s a great option for Upper East Siders and it’s going to really change people’s travel patterns," said Andrew Albert, an MTA board member. "It’s going to cut great amounts of time from their commutes — especially if they’re going to the West Side."

A 40-minute commute from 86th Street to Penn Station will now be reduced to 16 minutes, according to estimates from the Regional Plan Association. That prospect is expected to entice a chunk of commuters who currently struggle to pack into trains from the nearby Lexington Avenue line, which serves about 1.3 million riders each day.

There will be limited service at the new stations during the first few days to allow for the agency to continue testing elevators and escalators. Trains will run between 6 a.m. and 10 p.m. from Jan. 1 to Jan. 8, before 24-hour service launches.