San Francisco’s MUNI system of streetcars have a fare of $1.25. At least in the stations, they expect you to pay your way in change—the turnstiles don’t have bill slots.
Now, should you arrive at the station with your $1.25 in the form of a dollar bill and a quarter, you are instructed to proceed to the ticket machines for BART (San Francisco’s other public transit system). These machines have a special change dispensing mode: four quarters for a buck. So far, so good.
Should you arrive at the station with larger bills, things get interesting. There are change machines which will break a $10 bill or a $20 bill, giving you two or four $5 bills, respectively. Oddly, though, there is no machine in the station which will convert a $5 bill into $1 bills, and the MUNI agent who kindly explains all of the above details can’t make change for you, either.
When I ran into this situation this weekend, I popped above-ground, found a drug store, and bought a 49-cent ice cream sandwich with a $5 bill. I wasn’t expecting the cashier to say to me, “Do you have any more fives? We’re kind of short on them?” I gave her two more, and got back ten ones. Then I went and rode the MUNI.
The whole affair had a pleasantly symbiotic feel.