Next week DART, the T in Fort Worth, and DCTA are offering a week of free public transit to anyone who trades in a gas receipt. You have to do this in advance (can’t just hand a bus driver a gas receipt) by visiting one of the trade-in locations at the specific dates and times listed on this link. (There are opportunities today, tomorrow, or Saturday.)
The hope of the transit agencies is that they entice some commuters to make a permanent switch. There are a limited number of passes during each of these giveaway times, so I’m guessing you may want to get there earlier than later.