The OAA wagon could be seen as a logical progression of the open wagons of yore, they had no explicit purpose in mind upon introduction but to haul a large amount of cargo wherever was required. Introduced in 1971 with a carrying capacity of 31 tonnes the OAA wagons had drop side doors on each side for the easy loading and unloading of cargo. �The OAA wagons saw conversions and rebuilds within a few years of introduction as the railways undertook a move towards specific rolling stock for specific uses, and the need for general wagons became reduced. Many wagons would go on to enter departmental service. A small handful of the wagons are still in service, although these tend to be used as barrier vehicles in the modern era.
