Ride Public Transit For Free: San Francisco Bay, on All Aboard Bay Area Transit Day (May 6)

This is marketed with too short a time frame, but transit agencies should schedule a couple free transit days each year as a way to introduce people to and market the hell out of transit.  Such days can be used to launch coordinated improvements as well.

From the website:

Bay Area transit agencies in partnership with the Metropolitan Transportation Commission (MTC) and the Bay Area Air District are encouraging residents to ride transit on Tuesday, May 6, for All Aboard Bay Area Transit Day, coinciding with the start of Spare the Air summer smog season. 

All Aboard Transit Day encourages people to get out and ride transit – or perhaps try it for the first time – as more people return to the office and as transit ridership grows. On May 6, transit agencies will offer free stickers and other swag items to riders throughout the day to thank them for riding, while also soliciting their feedback.