ABOVE: When in doubt about littering, look for a helpful sign like the one above.

Have you ever wondered whether it was OK to throw your rubbish on the floor of a railroad station? At the Venezia Mestre station, the authorities have come to the rescue of uncertain travelers by posting a sign that gives an answer to that perpexing question. (In other train stations, you may need to inquire before deciding whether to toss your trash on the platform or use a wastebasket.)