UX anecdote: Half my Caltrain rides someone in the traincar screwed up their Clipper card usage. Examples + FAQ: tagged on but forgot to tag off - I've done this (every extra step = drop-off in task completion success). Or bought a monthly pass and didn't bother tagging on at all (why do you need to track rides if a conductor can tell you have a monthly pass for the current month and you're on the train within range of your pass? because you *might* go out of range?). Also the minimum $1.25 "credit" you have to maintain just to use 8-ride or monthly passes is ridiculous. That's just the start of the confusion - see their FAQ for more: caltrain.com/Fares/howtobuy/clipper/Clipper_on_Caltrain_FAQ.html