People traveling to New York or Philadelphia to see the pope are encouraged to use public transportation.
Metro-North is advising New York commuters to buy round-trip tickets in an effort to avoid long lines. The railroad is altering some schedules Friday to accommodate extra crowds.
Amtrak, meanwhile, is alerting passengers that all trains to Philadelphia on Saturday and Sunday require reservations. Extra trains with added capacity will run over the weekend.
"You need to plan your route. You need to be patient and understand there are going to be road closures, security inconveniences," said AAA spokesman Fran Mayko.
Heightened security will include restrictions on the size of backpacks, among other things.
Pope Francis will leave Washington, D.C. for New York City on Thursday and will head to Philadelphia on Saturday.