To cope with the unprecedented crowds anticipated for Pope Francis' visit in September, SEPTA plans to double its rail and subway capacity, limit train stops, and carry only Regional Rail passengers who purchased special passes in advance.

Officials of SEPTA, Amtrak, PATCO, and other agencies joined Mayor Nutter at City Hall on Tuesday to outline transportation plans for the papal visit and the World Meeting of Families.

As many as two million people are expected to jam the Benjamin Franklin Parkway to see the pope at a Saturday festival and again at a Sunday Mass on Sept. 26 and 27.

"Be prepared to walk at least a few miles or more," Nutter said, warning that "this will be the largest event in the city of Philadelphia in modern history." Nutter said he had been told to expect one million to two million visitors to Center City, but acknowledged, "I don't know how many people are coming."

The city needs to think about people who are elderly or disabled and "don't have the ability to walk miles, or even blocks," said Diane Menio, executive director at the Center for Advocacy for the Rights and Interests of the Elderly, a Philadelphia nonprofit.

Menio said she also was concerned about people who need to get around for such things as doctor appointments, and hoped that city officials "have a plan to accommodate older adults and people with disabilities who don't have other alternatives."

She added, "At least, at a minimum, help people understand what's happening."

SEPTA hopes to incorporate lessons learned from the 2008 World Series parade, when hundreds of thousands of people overwhelmed the system. This time, SEPTA won't try to operate trains to every station.

SEPTA will operate normal service during the World Meeting of Families, Sept. 22 to 25, but it will drastically alter service for the two days of the pope's visit. Regional Rail trains, subways, and trolleys will run truncated routes, with stops at only 31 stations instead of the usual 282.

A special $10, three-day SEPTA transit pass, valid from Sept. 26 through 28, will be sold for travel on subways, buses, and trolleys. Standard SEPTA passes and tokens can also be used on those transit lines. But on Regional Rail, passengers will need to buy a $10, one-day special pass for each day of the pope's visit.

Passes for the papal visit will go on sale July 15, only on SEPTA's website (www.septa.org).

Sales of Regional Rail passes will be limited to about 150,000, SEPTA officials said.

The Broad Street and Market-Frankford Lines are expected to carry about 200,000 people on each day of the pope's visit. Trolleys are expected to carry about 100,000 each day.

SEPTA officials expect tour buses to bring an additional 250,000 visitors to Center City.

PATCO trains, operating between South Jersey and Center City, will stop only at the Ninth/10th-Locust station in Philadelphia and the Lindenwold, Woodcrest, Ferry Avenue, and Broadway stations in New Jersey.

PATCO passengers will only be able to use a Freedom smart card. A one-day card will cost $5, and a two-day card will cost $10 for the two days of the pope's visit. The cards will go on sale in mid-July.

NJ Transit won't operate regular weekend service on the Atlantic City Rail Line or the River Line between Trenton and Camden. Instead, it will offer special tickets on those lines for an undetermined fare, starting this summer.

Amtrak will add cars to Philadelphia-bound trains and may add additional trains if demand warrants.

At Philadelphia International Airport, officials said, crowds for the week's festivities are expected to be similar to those on a Thanksgiving holiday, with as many as 100,000 people a day traveling through the airport instead of the usual 85,000.

Parking will be a major hassle for mass-transit riders, who are expected to overwhelm existing lots.

SEPTA officials said they are seeking additional parking in towns near the papal rail station stops, but they urged passengers to be dropped off near stations rather than try to park.

SEPTA will not run shuttles from outlying stations to those where trains will stop.

SEPTA plans to pick up passengers only at these stations en route to Center City:

Paoli/Thorndale Line: Paoli and Radnor.

Norristown/Manayunk Line: Norristown Transportation Center.

Chestnut Hill West Line: Chestnut Hill West.

Lansdale/Doylestown Line: Lansdale and Fort Washington.

Warminster Line: Warminster.

West Trenton Line: Woodbourne.

Fox Chase Line: Fox Chase.

Trenton Line: Croydon and Cornwells Heights.

Media/Elwyn Line: Media and Primos.

Wilmington/Newark Line: Wilmington and Marcus Hook.

Airport Line: Terminals C & D, Terminal B, and Eastwick.

SEPTA officials have not determined which Center City stations will be used for papal passengers, general manager Joseph Casey said.

On the Market-Frankford Line, westbound trains will only pick up passengers from the Frankford Transportation Center and the Girard Avenue station, and eastbound trains only at the 69th Street Transportation Center and the 52d Street station, with drop-offs at yet-to-be-determined Center City stations.

On the Broad Street Line, northbound trains will operate only from AT&T Station. Southbound trains will pick up passengers only at the Fern Rock Transportation Center and the Cecil B. Moore station, with drop-offs at yet-to-be-determined Center City stations.

Trolley service will operate on these lines: Route 15, service from 63d Street and Girard Avenue; Routes 11 and 13, service from the Darby Transportation Center; Route 34, service from 61st Street and Baltimore Avenue; Route 36, service from 60th Street and Eastwick Avenue. There will also be service from a limited number of stations on the Norristown High-Speed Line and Route 101 Media and Route 102 Sharon Hill trolley lines.

Donna Crilley Farrell, executive director of the World Meeting of Families, urged visitors and residents to check the website WorldMeeting2015.org for transportation updates and get a "papal visit playbook," a guide to navigating Center City during the event.

215-854-4587

@nussbaumpaul

Inquirer staff writer Robert Moran contributed to this article.