The Combined Nomenclature (CN), v1:2025
8604 00 00: Railway or tramway maintenance or service vehicles, whether or not self-propelled, e.g., workshops, cranes, ballast tampers, trackliners, testing
https://www.dst.dk/en/Statistik/dokumentation/nomenklaturer/kn?id=07469aa8-16e3-44d3-bd95-f5f4a5cf5be9