A lot of colleges have a card system for purchases. For instance, you can use a card to pay for your meals and get snacks as well as buy books at the bookstore. Colleges find this convenient to have a unifying system of electronic payment over the entire campus. It’s quick. It’s easy. It’s convenient.
Now, imagine now if an entire city used a card system. In Hong Kong, a card is called an Octopus and it is beautiful to see efficiency at its best. The card works nearly everywhere for small payments. The bus, train, trolley, and subway were the foundation for the Octopus system around five years ago. Now everything from Seven Elevens to carparks have the system of payment.
I don’t think an American city could ever get such unification because the details would always be squabbled over. But I must say, it is spectacular to see this system in action.