There is an extensive railway system – underground U-bahns and rapid transit S-bahns. You buy a ticket to ride at a machine near the entrance of the station, and then you take the ticket to another machine on the train tracks to validate it.
There are no barricades between the ticket machine and the validation machine. There are also no barricades between the validation machine and the train itself. Officials rarely come to check to see if tickets have been validated.
That’s all I’m going to say about that.