There are no turnstiles in the Vienna subway system.  There are only these pylons which let you know that you are entering the system.  Riders are on the honor system and are expected to have a properly validated ticket should they be challenged by the very rare conductor.  The blue boxes are a sort of time clock used to validate certain types of ticket.  Not having a properly validated ticket when challenged means being fined 50 to 80 times the value of a ticket.
Oddly, this system seems to work OK.  The Schnellbahn authorities have made the conscious decision that any potential lost revenue from cheating is more than offset by not having the substantial expense of an elaborate ticket issuing/validating/collecting/accounting system.
The Schnellbahn is almost totally automated.  I have observed trains that appeared to have no one at the controls.  Displays above each track tell the waiting passengers how long before the train arrives, what route the train is travelling, and whether or not it is a short train (Kurzzug).