PHILADELPHIA — Pilgrims heading to Philadelphia to see Pope Francis will face many travel restrictions in the city and need to start looking at transportation options now — and should anticipate walking about two miles a day, officials said.

“Private vehicles will really not be a viable option,” Mayor Michael Nutter said.

Several officials joined Nutter to discuss preliminary transit information at a news conference about 100 days before the Sept. 26-27 papal visit, which could draw a crowd of 1.5 million.

Their main message: Plan ahead, way ahead. And have a backup.

The Southeastern Pennsylvania Transportation Authority will open only 31 of its 282 subway, trolley and commuter train stops that weekend. That will allow for express service from the outer suburbs and neighborhoods to downtown, said SEPTA general manager Joseph Casey.

Regional rail riders must pre-purchase a $10 daily pass for each day of weekend travel. The passes go on sale July 15; none will be sold while Francis is in town. Casey noted that parking will be challenging at those suburban stations. Officials continue to work on access to satellite lots, he said, and hope many people will simply be dropped off.

SEPTA will offer a three-day pass for bus, trolley and subway service that costs $10.

Overall, SEPTA expects to serve 650,000 to 700,000 passengers each day of the pontiff’s visit, more than double the system’s normal load.

On Sept. 26, the pope will attend a closing festival downtown for the triennial World Meeting of Families, a Catholic conference designed to strengthen family bonds. On Sept. 27, he’ll celebrate an outdoor Mass on the Benjamin Franklin Parkway.

Nutter cautioned that these appearances will cause much more congestion than traditional large-scale festivities like the city’s annual July Fourth concert and fireworks, which draws hundreds of thousands of revelers.

“We need to really help people understand this is a very different event,” Nutter said. “(You) should not necessarily anticipate that you’re just going to pull up and park your car and jump on the train. That’s not happening.”