We feed the parking meters in our town with Smart Cards. When we park, we charge the car for the maximum time we might need. Upon our return, we insert the card to get a refund for unused time. The parking meters stand in pairs, for each two spaces. If only I did not have a tendency to put my Smart Card in the wrong meter!
I returned this morning to find a meter patrolman eying my car. “Look,” I said to him, “You’re about to give me a ticket because I fed the wrong meter. I’ve got 43 minutes coming to me in the empty space behind my car.”
“Well then,” he said, “Backup!” And he drove away.