I was born in Denmark, in the suburbs of Copenhagen. Depending on how you define "railway journey" it would therefore very likely have been a trip on the S Train.
(Funnily enough the S probably stands for the Danish word for "station". When the lines were turned into this commuter network, they used an "S" as a prominent sign of where the stations were. The public didn't really know what the "S" stood for, just that it showed where the trains were, so when a newspaper launched a competition to formally name the network, "S-tog" ("S train") won.)