But "double ticketing" involves passing the ticket through twice in the same direction - what I am referring to is going through in one direction & coming back in again in the opposite direction, using a totally different gate.
Are you seriously saying that the gates can't tell the difference between "coming in" & "going out"?
Even if this is the case, a time delay of 5 minutes would seem more than sufficient!
It can tell the difference, but not that many people break their journey for such a short amount of time.