Hello,
Does anyone know if I purchase a single journey train ticket from Amsterdam to Koblenz at the station, would it allow me to get off to see Cologne, and get back on later? Thanks!
If you purchase a full fare ticket, yes? If you purchase a reservation, it's train specific, so once you get off the train, the reservation no longer works. If you are getting a Europa-Spezial ticket, you can build in a stopover in Köln (I did that in 2008), or you can use the stopover function and the Mode of Transport to specify a regional train to Koblenz. The Europa-Spezial fare does not make use of the specified regional trains mandatory. You can use any regional train to your destination as long as you finish the trip by 10:00 the next day.
I can read between the lines that you have some reason for ending up in Koblenz. But Cologne is a more attractive city, with even more to do than Koblenz. Be sure you consider how you are paying for your subsequent travel to see if Cologne might not cost any more for an overnight. I mean, for example, if you have a boat ticket that's good all over the Rhine, not just from Koblenz. (I realize that it eats up more time to start the boat in Cologne.) We did find that Koblenz, or actually Andernach, where we slept, is a better location for cheap day tickets on the train to see the key segment of Rick's Rhine .... But Cologne has a lot going for it.
Note: there is only one K-D boat per day that starts in Köln (Cologne), and it doesn't go all of the way to Koblenz. (www.k-d.com)