technically, possessing two transfer tickets from the same day could be used as proof that you paid enough for the day.
vienna has day tickets that cost as much as two single tickets but you can only buy them on a strip of 8 which you can use one day at a time over an unlimited period
vienna has day tickets that cost as much as two single tickets but you can only buy them on a strip of 8 which you can use one day at a time over an unlimited period