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Between the shutting down of major highways, miles of security perimeters and the deployment of thousands of additional law enforcement officers on the streets, officials in Philadelphia believe that they are ready to handle Pope Francis' visit – and the influx of millions of faithful Catholics – later this month.

The question on many people's minds, however, “Is all of it really necessary?"

Despite the revelation on Sunday by House Committee on Homeland Security Chairman that federal agents have already “disrupted one particular case” of a threat against the pope, public safety and counterterrorism experts have been questioning the scope of Philadelphia’s plans – especially given the large security detail the Vatican sends with Francis everywhere he travels.

"You have to look at if the response to threat is proportional or not," Scott White, a professor of national security at Philadelphia's Drexel University, told Fox News Latino. "I get the fact that we need to have a free flow of people and proper security, but the issue people are asking is, 'Why can't this be localized to one area and leave the rest of the city operational?"

White added, City Hall "is not doing a good job of explaining this."

Mayor Michael Nutter announced in August that the city would be shutting all of its Center City area to vehicle traffic beginning the evening before the pope's visit, along with closing the Vine Street Expressway – the main highway running through the heart of the city – and other expressways as much as 14 miles outside the city.

The Benjamin Franklin Bridge, which connects the city to Camden, New Jersey, will be closed starting the night of Sept. 25, and SEPTA, the metropolitan area's bus and rail service, plans to close all but 21 train stations and to require special papal passes to travel on its commuter trains.

Secret Service Pope Visit Map by PhiladelphiaMagazine

With officials expecting 1.5 million people to descend on the city of about 1.5 million for the pope's visit, some experts are concerned that the massive road and public transportation closures will prove to be a major disruption for residents, businesses and visitors alike.

"You have to do security in a way that doesn't ruin the primary purpose of the event. You want to try to not disrupt the city too much." Henry Willis, director of the RAND Corporation's Homeland Security and Defense Center in Pittsburgh, told the Philadelphia Inquirer. "You've got to balance control, based on what you know, versus the purpose of the visit and the disruption that you're causing."

For those who do manage to make it into Center City for the pope's visit – or those who live or work within the security barriers – getting around town won't be very simple.

In August, Nutter outlined security measures that begin taking effect two days before the pope arrives. These include a patchwork of security zones with designated entry points – which will have metal detectors – and exit points.

The Secret Service last week outlined additional security zones that include the two fenced-in areas where Francis is scheduled to speak – in front of the Philadelphia Museum of Art, where he is saying Mass, and Independence Hall, where his is speaking about immigration. Together, the two security zones are larger than Vatican City itself.

In contrast, the cordons in New York City will be much more localized, according to a release issued jointly by the Department of Homeland Security, the New York Police Department, the Coast Guard and a number of other public safety agencies.

The largest, involving the papal motorcade on Sept. 25, will make Manhattan’s Central Park off-limits to those without tickets, but shouldn’t disrupt much of the city’s commercial life.

Washington D.C. Mayor Muriel Bowser has advised people to work from home if at all possible, during the pope’s visit to the capital. Some major roads, like Massachusetts Ave., will be closed for three days. But only certain parts of the city – near Capitol Hill – will be impassable.

While Philadelphia hasn't released the number of police officers that will be called on to maintain order during the visit, Pennsylvania Gov. Tom Wolf has chipped in, providing 1,000 state troopers and a yet-to-be-determined number of National Guardsmen.

Counterterrorism experts argue that despite the security measures, there are still chances for terrorist groups or so-called "lone wolf" actors to cause massive damage. Terrorist groups could have already set-up operations within the city's security ring long before the precautions are enacted and while a "lone wolf" may not be able to get close to the pope, he or she could still get close to a crowded security checkpoint.

"We have ample examples of these types of attacks right up to Boston," White said. "You can push back the layers of security only so far before you have a chokepoint."

He added, "A terrorist, a mentally ill person or anybody who wants to execute something will be able to do it. Whether it is in Philadelphia or across the Ben Franklin Bridge in New Jersey is not going to matter to the families of the victims."

Both local and federal officials have said they have heard the complaints about the security measures, and that they want to take a better-safe-than-sorry approach, especially with mounting concerns over homegrown terrorism and mass shootings.

And the pope has to be taken as a credible target of an attack. On ABC’s “This Week” on Sunday, House Homeland Security Chairman Mike McCaul (R-Texas) said, “We are monitoring very closely threats against the pope as he comes into the United States.”

He added, “We have disrupted one particular case.”

In 1981, Pope John Paul II was the target of an attempted assassination in Vatican City.

Security concerns in Philadelphia go beyond the scheduled papal events. When Pope Benedict XVI visited the United States in 2008, federal authorities issued a 19-page joint threat assessment concluding that while there was no credible threat to the Masses that were to be held at the Washington Nationals' ballpark, they warned that terrorists could make attempts on "'softer' targets such as hotels, public gatherings, restaurants or transportation modes."

Adding to the worries for the Secret Service is Francis' penchant for shunning security measures and making unexpected stops during his foreign visits.

“I'm concerned,” McCaul said on Sunday. “He is a very passionate man. He likes to get out with the people. And with that comes a large security risk.”

The Secret Service, working with the FBI and local authorities, has spent months coordinating the security effort. Secret Service officials have met multiple times with Vatican officials both in Washington and in Rome to learn more about how the pope interacts with crowds.

Francis travels with his own security detail, and the Vatican arranges for the exact configuration of his "Popemobile" – for this visit, a tricked-out Jeep Wrangler.

With previous pontiffs, all sides of their Popemobilies were encased in reinforced glass, but Francis disliked the feeling, saying it was like being in a "sardine can." The Jeep he rode around in during his recent South American swing was open on the sides, allowing him greater interaction with the crowds, but also potentially causing greater security headaches.

Despite the concerns, Philadelphia officials seem confident that the Francis' visit will go off without a hitch, given the city's history of hosting major events like the World Series and political conventions.

"Philadelphia is the 'Can-Do City,' and we can do and will do everything in our power, along with our many partners, to ensure a safe and secure event – a spiritual and joyful event," Nutter said during a press conference. "It will also be one of those rare opportunities for Philadelphia to showcase on a global stage what we've been doing for quite some time – managing very large events or situations."