What to Know Construction on current iteration of the Second Avenue line began in 2007 but planning for it stretches back generations

Under the first phase of the project, trains will run from 63rd Street to 96th Street at 72nd, 86th and 96th streets

The second phase will extend the line up to 125th Street

Service to the public on the Second Avenue subway will begin on New Year's Day, Gov. Andrew Cuomo told NBC 4 New York during a one-on-one station tour Sunday.

A ceremonial ride on Dec. 31 will usher in train service on the first phase of the line — a three-stop extension of the Q train that has been a century in the making.

Just hours after Cuomo said "we'll make a final call very soon," he confirmed Sunday that the subway will be up and running for the public on Jan. 1.

Cuomo, who controls the MTA, said a final call will be made this week: "This week for sure!"

Construction on the current iteration of the Second Avenue line began in 2007, but it has been in planning by the city since 1929 and was first proposed by a Public Service Commission engineer in 1919 as part of an expansion of the transit system.

Under the $4.5 billion first phase of the project, trains will run from 63rd Street to 96th Street. The second phase will extend the line up to 125th Street.

The governor said the new Q subway stations — at 72nd, 86th and 96th streets — give riders a sense of space and air, and that rubber tracks will quiet the noisy trains as they roll into the stations.

"When have you ever had that sense in the subway system?" he said. "Architecturally, the design, it's much more open."

Critical safety tests on elevators, escalators, smoke alarms and fire radios weren't scheduled to be done until right before Christmas, the MTA said earlier in December.

By Sunday, the lead engineer said that the 86th Street station had passed the tests. The 72nd Street station, however, was still being tested.

The MTA said on Dec. 12 that the subway station was on track for a Dec. 31 completion date, but would not confirm an exact day for opening. MTA chairman Thomas Prendergast said he was "cautiously optimistic" that it was going to meet the revenue service date.

Just a few days before the Prendergast's announcement, Cuomo said that he too was "cautiously optimistic" the long-delayed subway would open early in the New Year. He tweeted the remark after surveying the new East Side subway line.

Many Upper East Side residents said they were skeptical the new line would be able to open this month. Streets were filled with construction crews and escalators were still being installed.

"There's still so much going on — so much construction they won't be ready for passengers," Upper East Side resident Susanna Cselenyi said.

Cuomo promised that street life will be better in the neighborhood once the new subway stations open and traffic flows more freely. He wants everyone to come together at the end of the month for the historic moment.

"The mayor, you are invited, the deputy mayor all New Yorkers because this is cause for celebration," he said.