Very cool -- I was not aware of this. It's interesting that RFID developed out of, partly, a desire by freight train operators to track traincars as they moved

Very cool -- I was not aware of this. It's interesting that RFID developed out of, partly, a desire by freight train operators to track traincars as they moved around switching yards (moving past fixed readers). The Eurobalise system is sort of the reciprocal of that idea.