Originally Posted by
Flying Lawyer
True for the S-Bahn and the U-Bahn, different for busses and tramways. There simply is not chance to stamp the ticket in the S-Bahn and the U-Bahn.
P.S.: And this is true for other cities with real Subway system (which Cologne does not have) and all S-Bahn trains nationwide.
Understood. Thank you very much for explaining. I didn't know all this prior to you guys explaining.