The change means officers are no longer required to patrol in pairs, with Adams revealing the change to Bill Ritter on the Eyewitness News program "Up Close."
"That's what I did as a transit police officer during the '80s," Adams said. "We are going back to that because that was one of the ways we were able to bring down crime."
The NYPD did away with solo subway patrols in 2014 after officers Wenjian Liu and Rafael Ramos were murdered in Brooklyn.
The locations will be fluid, and the patrol plan covers train lines that travel through every borough in the city, except for Staten Island.
"The officers doing solo train patrol will stay within one district on one radio division, patrolling the lines and train stations that they are the most familiar with, keeping them in close proximity to support, quick backup and within accessible range of their supervisors," NYPD Transit Chief Jason Wilcox said. "They will be close enough to stay on the same radio frequency and always be in contact with each other.
Some stations will remain dual patrol, and overnight police officers on train patrols will be paired -- but they won't be standing together.
"We will cover more ground by patrolling more subway cars per tour," NYPD Commissioner Keechant Sewell said. "An increased police presence leads (to) a safer ride for customers and MTA personnel alike."
Adams also said the city and MTA will launch a massive campaign to teach riders how to be a safe passenger, saying riders must remain vigilant and citing female passengers he recently saw standing in "isolated areas" late at night.
"That is just unsafe," he said.
MTA Chairman and CEO Janno Lieber praised the mayor and NYPD for the move.
"We know this from our surveys," he said. "Seeing a uniformed officer on the train is really reassuring. It's the one thing that makes people feel really safe on the system."
And Adams said that is the goal of the shift.
"That is playing a major role in people feeling comfortable about riding the subway system," he said. "We are getting ready to announce the next layer of our subway safety plan, moving away from the double patrols that cut our police force in half and going back to single patrol to have the omnipresence that is needed in our trains and stations. We want to continue to modify until we bring back that level of confidence that New Yorkers need."
The move was not without critics, though, including the Patrolmen's Benevolent Association.
PBA President Pay Lynch blasted the policy, saying it will force police officers to retire.
"We can't fix the NYPD staffing crisis by spreading our overstretched resources even thinner," he said. "Solo transit patrols were abandoned because they make it harder for cops to protect straphangers and ourselves. They're even less effective now that criminals know there are no consequences for fighting cops and resisting arrest. New York City police officers are overburdened, underpaid and leaving in droves. This proposal will only accelerate the exodus."
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