How old do you have to be to purchase an Amtrak Train ticket?

When are you allowed to board a German train without a ticket but purchase one on board?

• My vacation will be in Germany this summer and I want to clear something up before I go there. I sometimes see people presenting their tickets to the guy who checks the tickets (sorry forgot the name) inside the train meaning they had purchased the ticket before boarding. While other times I see them purchasing the ticket on board (the guy asks for the ticket and the passenger buys it on the fly). So when is this allowed? I know that you can be fined for not buying the ticket before boarding but when is the exception to this?

• Answer:

  For trains operated by Deutsche Bahn (DB): It's allowed only on long-distance trains (IC/EC and ICE), but not on regional trains like RB, RE, S-Bahn, or local U-Bahn. You can pay cash or by credit card. There will be an extra charge, and you can't use special-offers. For CC payments of 50 Euros or more you may be asked to show a photo ID (passport or official ID card) to make sure you're the legit owner. http://www.bahn.de/p/view/service/vertriebswege/7wege_fahrkarte.shtml?dbkanal_007=L01_S01_D001_KIN0011_service_VR1-7W_LZ01 However, some regional lines (RB) are operated by other railway companies than DB and may have ticket machines onboard (e.g. the Nordwestbahn in Lower Saxony), but you have to make sure beforehand. http://www.nordwestbahn.de/de/fahrkarten-tarife/fahrkartenautomaten.html