The New York subway signs experiment.

NYC subways have a strange rule. Before opening the train doors, a conductor is required to point at the sign to acknowledge (for safety reasons) that the train has fully arrived in the station.
Rose Sacktor and Yosef Lerner, roommates and a former art director/copywriter duo at Miami Ad School, decided to use this little-known gesture as a way to acknowledge and even entertain the conductors who work so hard to shuttle NYC commuters around each day.

 "Conductors spend their whole day in that small booth, alone. It is incredibly loud, and they get minimal human contact. We decided to show our appreciation for their work."