The Combined Nomenclature (CN), v1:2023
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=72c00acf-45ba-43e2-9d08-63bdac4ce8a8