Year of entry into service:
Westrail introduced the N Class in 1977 for freight service in Western Australia. Four were modified and reclassified as the NA Class, with two of these later being converted to standard gauge and reclassified as NB Class units 1872 and 1873. These two units were in service with Austrac from 1998 until 2002, where they were classified as the 18 Class. 1872 was scrapped in 2020, while 1873 is owned by Australian LocoLease and is currently stored.