Travel on regional cross-border connections
In the Netherlands, you simply travel on these trains using your OV-chipkaart. You check in and check out with the operator running your journey.
Are you crossing the border? Then you need to buy an international ticket. You can get this via NS, NS International service desks, the NS International Customer Service, or from ticket machines of foreign operators at border stations, such as NMBS, DB, Arriva, VIAS Rail and Keolis.