For East Harlem, the news has been a long time coming — a subway along Second Avenue in the neighborhood was first proposed nearly a century ago .

Many people who live and work in the area said they would welcome the new service, though some raised concerns that it could accelerate development in the largely Latino and black neighborhood where gentrification has already taken hold.

“We’re always worried about that,” said Robert Rodriguez, a state assemblyman who represents the neighborhood. Still, he added, “I don’t think that’s a reason to not provide essential amenities.’’

The neighborhood now relies on the Lexington Avenue subway, which can be a long walk for some residents and where trains can be so packed that riders sometimes have to let a train go by before they can get on.

“There are working people that rely on public transportation to get around and we don’t have a fail-safe if anything happens” with the Lexington Avenue line, Mr. Rodriguez said. “There is no backup. There is no other line for East Siders.”