The card system would probably be best where just buy a card and load it up at a kiosk. There would still be potential security vulnerabilities if you were allow someone to "anonymously "view that transaction. Or allow someone to view the card trips. Which would just be logged with its number.
And I’m just more so talking about the current system they have in place. I’m not sure what else they could do utilizing their current system except for forcing some kind of account