“It’s about getting more fair outcomes without sacrificing public safety,” Mr. Vance said in an interview this week as the plan was being completed. In most cases, he said, “these guys just don’t need to be arrested and processed in the justice system.”

But the plan has yet to win the unequivocal support of the police commissioner, James P. O’Neill. On n Friday Mr. O’Neill was working with Mr. Vance’s office but had yet to reach an agreement on how and when to divert fare-evaders from criminal court. The police still need to control subway entrances, Mr. O’Neill said. “We have to take a real serious look, if we’re going to make a move like that, you know, what are the implications for public safety?” he said.

As the district attorney, however, Mr. Vance has unique leverage: If the Police Department does not embrace the diversion program, Mr. Vance’s prosecutors can simply decline to prosecute any or all of the 10,000 fare-evasion cases his office handles each year — a step his aides say he is willing to take.

The new policy, announced Friday morning along with two other programs, is the latest in a series of efforts by prosecutors, the Police Department and Mayor Bill de Blasio to recalibrate the tough enforcement of petty crimes that the city pioneered in the 1990s. Catching fare-beaters was a cornerstone in that policing strategy, started under Mayor Rudolph W. Giuliani, along with vanquishing public urination, panhandling, street prostitution and so-called “squeegee people” who wiped car windshields with dirty rags.

While the effort was lauded in many circles for helping drive down crime in New York City, the collateral consequences of such aggressive practices, particularly for young black and Hispanic men, have come under pointed criticism, especially in a time of record-low crime. There is a growing consensus among city’s liberal policy makers, among them Mr. Vance and Mr. de Blasio, that tough enforcement of petty crimes has burdened a whole generation of New Yorkers, most of them minorities, with criminal records that undermine their job prospects.