NEW YORK (CBSNewYork) — Details are emerging about the “massive” and “complex” security plan being worked out for Pope Francis’ visit to New York City next month.

As CBS2’s Marcia Kramer reported, the NYPD and federal agencies are faced with the specter of terrorism, the fact that 160 heads of state will be in the city at the same time as the pope for the United Nations General Assembly and the complexities of protecting a pope who likes to mix with his flock.

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“It’s going to be an unprecedented challenge for this department,” police Commissioner Bill Bratton said Monday.

“It’s going to be a massive operation, a complex operation and one, as the commissioner will remind us, that a city has to live and breathe and operate around at the same time,” added John Miller, the NYPD’s deputy commissioner of intelligence and counterterrorism.

Operate? Yes. Quickly? Maybe not. Frozen zones can mean massive traffic congestion.

And there’s also the headache of how to protect the pope when he celebrates Mass at Madison Square Garden, right above Penn Station, the busiest train station in North America. Some 600,000 commuters use the six subway lines, the Long Island Rail Road, NJ TRANSIT and Amtrak that pass through the hub.

Worries about terrorism will mean that several entrances to Penn Station will be shut.

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But that’s not all.

Sources tell CBS2 that plainclothes cops will be riding the trains and subways and that one of the more unusual assignments will be to guard certain structural columns inside the station. Also, a way to detect a possible device aboard a train or tunnel is something officials are working into what they call the “counterterrorism overlay.”

And the NYPD will have cops doing everything from directing traffic, to using long guns for rooftop sniper patrols, to radiation detection on land, sea and air.

“Traffic, significant challenges with crowd control … (and) you have to treat any specter of terrorism,” Miller said. “So we’re going to have a significant deployment of uniformed personnel, a significant counterterrorism overlay on the part of the intelligence bureau and the counterterrorism bureau and a very significant partnership with the Secret Service.”

Since the pope’s visit has been designated a national security event, the Secret Service will be the lead agency. That means that all the assets of the Department of Homeland Security will be at the city’s disposal.

The pope will arrive at JFK Airport on Sept. 24 and attend evening prayer at St. Patrick’s Cathedral. The next day, he will address the General Assembly, host an interfaith service at the National September 11 Memorial & Museum, visit a school in East Harlem and celebrate Mass at Madison Square Garden.

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Francis will also visit Washington, D.C., and Philadelphia.