The event, "No Pants! Subway Ride 2013," expects to have a similar turnout as it did a year ago, when more than 600 BART and San Francisco Municipal Railway riders rode pants-free.
Riders are scheduled to come in two waves, and all will convene in from of City Hall in San Francisco for a group photo, according to the event's Facebook page, www.facebook.com/events/471254752925571
The first wave, coming from all stops on BART and MUNI will arrive at about 1:15 p.m. at Montgomery Station in San Francisco, according to the event page.
While that group walks down Market Street, the second wave of riders will meet up with them at about 1:35 p.m. at the Civic Center Station.
The event is described as improvisational to get reactions from people unaware of the day's plan.
Pants-free people are encouraged to walk into stores, bars, bathrooms and malls to get reactions from people, all while acting as if they are unaware why people are looking at them curiously.
This annual events has Facebook pages on events dating back to 2010, and is intended on being a light-hearted display.
Anyone interested in joining the pants-free participants are advised of four requirements: have a willingness to take pants off before boarding the subway; are able to keep a straight face; have at least $10 to ride on BART or MUNI (plus extra for bar visits); and absolutely no nudity.