NEWARK, N.J. - New Jersey's transportation agencies announced Thursday the road closings and special transit schedules they will put in place when Pope Francis visits Philadelphia next month, warned of massive crowds and traffic delays, and urged those unable to walk long distances to keep clear.

"We can only get so many people into Philadelphia," Transportation Commissioner Jamie Fox told a news conference at Pennsylvania Station on Thursday morning.

"If you're not prepared to walk a considerable distance," he said, "you may want to reconsider your attendance."

As many as 800,000 visitors are expected to make their way to Center City on Sept. 26, when Pope Francis speaks on Independence Mall and visits the Festival of Families on the Benjamin Franklin Parkway following the World Meeting of Families.

An estimated 1.5 million people are expected to attend his Mass on the Parkway the following afternoon, and an estimated 53 percent will be elderly, according to the events' organizers.

The two major expressways in South Jersey will remain open during Francis' visit, but Transportation Department officials said that if traffic backs up dangerously on the New Jersey Turnpike or I-295 because of an abundance of vehicles seeking to exit toward Camden, they will close those exits and direct drivers elsewhere.

The region will see a "massive influx of vehicles," officials said, announcing that the Commodore Barry, Walt Whitman, and Betsy Ross Bridges would remain open.

Mayor Nutter said last week that the Benjamin Franklin Bridge would be closed to vehicles from 10 p.m. Sept. 25 until about noon Sept. 28, but that three lanes would be open to pedestrian and bicycle traffic.

Because of the Ben Franklin closure, the New Jersey Transportation Department said Thursday that it would also close I-676 westbound from Exit 3 to the bridge and the Admiral Wilson Boulevard westbound from the Airport Circle to the bridge.

It also said Routes 38, 42, 45, 47, 55, 70, 73, 90, 130, 168, and 322 could experience significantly increased traffic, and warned of congestion and delays on I-95, and I-195, and Route 1, and "much-heavier"-than-normal volume on the turnpike and the Atlantic City Expressway.

Detours and electronic message signs will be posted to divert traffic onto northbound and southbound Route 130 to get to other crossings into Philadelphia, the agency said.

Parking in downtown Camden will be restricted to the about 1,100 buses that have been registered with the organizers.

Fox and other transportation officials held a second news conference Thursday afternoon at the Walter Rand Transportation Center in Camden.

Sam Schwartz, a traffic engineering consultant for NJDOT, warned that visitors who arrive in Camden by bus and make the trip to Philadelphia on foot might not get back to their buses until dark, because of crowds leaving the city all at once, and the slower pace of many of the seniors expected to attend.

He said people who plan to do a lot of walking that day should bring flashlights, extra cellphone batteries, and extra medication, if necessary.

"This is not an easy hike," he said, noting that crossing the Benjamin Franklin Bridge involves a vertical gain of about 135 feet. "We want people to come, but we want them to be prepared," he said.

After the Camden news conference, transit officials began leading a group of reporters through downtown Camden and over the bridge's pedestrian walkway. Some, including NJ Transit director Ronnie Hakim, made the entire 4.5-mile trek from Camden to the Philadelphia Museum of Art.

Walking briskly, the trip took about an hour and 40 minutes without a break, Hakim said later. It would likely take longer for many seniors, officials estimated.

"The idea was to understand what our customers might be experiencing," Hakim said. "And so that we can let people know what to expect."

Officials, apparently making allowance for the many senior citizens expected at the papal events, displayed a graphic showing the estimated walking times from Camden into Philadelphia - three to four hours for five miles, six to seven hours for up to 11 miles.

Emergency vehicles will be posted in emergency lanes in the event of health problems as people walk to Philadelphia, officials said.

The NJ Transit Atlantic City line will run on an express schedule that Saturday and Sunday between the Shore and 30th Street Station.

The RiverLine will be on an every-15-minute schedule, but will stop only at Bordentown, Florence, Burlington South, Route 73, Pennsauken, and Camden. It will have extended hours as needed officials said.

Special tickets - $5 round-trip - will be required for the RiverLine. Similar special tickets will be required for the Atlantic City line, at $30 round-trip.

The tickets go on sale Saturday and will be available only for advance purchase. No tickets will be available for purchase the day of the event, and monthly tickets will not work.

When the Ben Franklin Bridge is closed to vehicular traffic, all Philadelphia bus routes will end at the Walter Rand Transportation Center in Camden.

Access Link, NJ Transit's ADA-paratransit service to and from Philadelphia, will be suspended from Sept. 25 through 28. It will resume regular reservation service on Sept. 29. All Access Link service in and out of Camden County will be suspended Sept. 26 and 27.

Drastic road closures were also announced last week in Philadelphia, including shutdowns on I-76 and I-676, and a zone in much of Center City where cars that exit during the papal visit will not be permitted to return until hours after Francis departs.

All roads in New Jersey leading to New York City will remain open, officials said, noting that the pope's visit there includes no public event of the magnitude of the Mass he is to celebrate in Philadelphia.