It doesn't work on the GVB Amsterdam local trains or trams...just the NS trains. There are some routes within Amsterdam that have NS trains paralleling GVB trains, might help save money on those.
It doesn't work on bus, metro or tram, which GVB operates, but it does work on trains from all operators, not just NS.
It doesn't work on bus, metro or tram, which GVB operates, but it does work on trains from all operators, not just NS.