South Australian rail broad-narrow-broad swap adds to three-gauge confusion in places like Port Pirie

Port Pirie became renowned as a junction for trains on Australia's three different rail gauges.
Image courtesy State Library of South Australia
South Australia became the epicentre of the Australia’s problem with railway line gauges’ three sizes: broad (1600mm or 5' 3"), narrow (1067mm or 3' 6") and standard (1435mm or 4' 8½"). By 1917, South Australia had lines with the three different gauges – plus some other uncommon gauges.
The Irish broad gauge was initially adopted by South Australia, along with Victoria, Queensland, Western Australia and Tasmania. New South Wales’ lone choice, to use the European standard gauge, meant a disjointed national link.
But South Australia created its own disconnect between broad and narrow gauges. It started with broad gauge for lines out of Adelaide and the intercolonial railway between Adelaide and Melbourne, completed in 1887.
Broad gauge tracks could carry trains at higher speeds and greater comfort for passengers than narrower gauges but they were much more expensive to build.
This cost factor influenced South Australia to follow Queensland Railways and switch to narrow gauge. The Port Wakefield line (originally horse drawn and opened in 1870) changed from broad to narrow gauge while it was being built.
Because narrow gauge tracks started as isolated lines from independent ports at Port Wakefield, Port Pirie, Port Augusta, Port Lincoln, Port Broughton, Beachport, Kingston SE, Wallaroo and a private tramway from Whyalla, the problems of disconnected gauges were not immediately apparent.
But when the broad and narrow systems met at Hamley Bridge, Terowie, Wolseley and Mount Gambier, the complaints started.
Longer lines to Cockburn (on the South Australia-New South Wales border) and Alice Springs were also built to this narrow gauge. In the 21st Century, only isolated narrow gauge grain lines of Eyre Peninsula remained.
As it was realised that lightly-laid narrow lines couldn’t support large tonnages, South Australia continued to extend or convert lines to broad gauge. The Murray Mallee lines were built to broad gauge, the mid-north lines were converted in the 1920s from narrow to broad, and all of the lines south of Wolseley (apart from Glencoe) were broadened during the 1950s.
In the 20th Century, the federally-owned Commonwealth Railways joined New South Wales in adopting the standard gauge that eventually enabled the first national railways link.