There is no possibility to link a VehicleType to a TransportMode, although the NeTEx Part 1 documentation already states: "A VEHICLE TYPE shall belong to one TRANSPORT MODE" (par. 7.7.3.1 TRANSPORT MODE - Conceptual model). We also need this link for the Dutch NeTEx Profile.
Probably the TransportSubmode is not needed here, since most values of the xxxSubmode enumerations more concern the kind of service and not the kind of material.
It also does not make sense to allow more than one TransportMode.
There is no possibility to link a VehicleType to a TransportMode, although the NeTEx Part 1 documentation already states: "A VEHICLE TYPE shall belong to one TRANSPORT MODE" (par. 7.7.3.1 TRANSPORT MODE - Conceptual model). We also need this link for the Dutch NeTEx Profile. Probably the TransportSubmode is not needed here, since most values of the xxxSubmode enumerations more concern the kind of service and not the kind of material. It also does not make sense to allow more than one TransportMode.