Engines for auxiliary railway vehicles and auxiliary engines for railcars and locomotives are included in the categories NRE or NRS, according to their characteristics.
Déantar innill le haghaidh feithiclí cúntacha iarnróid agus innill chúntacha le haghaidh carranna iarnróid agus innill fhéinghluaiste a áireamh i gcatagóir NRE nó NRS, de réir a gcuid saintréithe.