They were a development of the Western Australian Government Railways R class and were the last of a line of very successful locomotives fitted with the English Electric 12CSVT Mk II engine.
With the construction of the new line from Launceston to Bell Bay, the Tasmanian Government Railways placed an order for four 1752 kW locomotives with English Electric.
[4][5] In March 1978 the Z class were included in the transfer of the Tasmanian Government Railways to Australian National.
[8] All four locomotives were modified for driver-only operation between 1998 and 2001, by having their noses lowered further and the size of the front cab windows increased.
In 2022, The Q Train acquired Z1 and Z4 for revenue use on their restaurant rail services on the Bellarine Railway.