This picture shows three ways I have paid for transportation in China:
The green card at the top is the wonderful, convenient, and all-purpose Shanghai Transport debit card. It is more modern than anything in the United States. You add money to it at a subway kiosk -- for me, usually 100RMB at a time, or $13.50. Then whenever you use almost any kind of transportation in Shanghai -- a subway, a bus, a ferryboat, and, crucially, a taxi -- you swipe the card across a reader and it deducts the fare. The joys of never having to find change for taxi fare are hard to imagine until you've experienced them. (Plus the joys of flat-fare non-tipping, a subject for another day.)
The pinkish paper ticket in the middle is a 2RMB (27 cents) fare for a ride on the Beijing subway system. It's less modern than what you'd find almost anywhere in the United States. You buy these one by one from vendors, and as you enter the subway an attendant tears off a stub. As the technologists would say, this approach does not "scale."
The blue card on the bottom is Beijing's new version of the Shanghai card, though (as far as I can tell) good for subways only. I haven't seen a taxi with one of Shanghai's ubiquitous card-readers -- and even in the subways the readers are still being phased in. This afternoon, in the downtown Guomao station, I saw lots of card-readers waiting to be installed. They're the things in the tasteful pink-plastic protective wrappers:
Soon people won't be able to imagine it was ever done any other way.