We recently rode the Metra train to and from Chicago. On our ride home, the conductor walked into our train car announcing, "This is a quiet car! Collecting tickets!" I thought he was just making a comment about how quiet it was on the train. Apparently he wasn't kidding. I saw this sign as we were getting off the train.
I guess when people put in a hard day at work (or shopping!) the last thing they want to hear is a crying baby or kids fighting or loud music. It's a good thing I didn't fall asleep or I'd have gotten kicked off with my loud snoring!
For more signs, visit Lesley here.