During the construction phase of the Trans-Australian Railway, the Commonwealth was obliged to find cheap locomotive power at short notice. This resulted in the purchase of various surplus second hand units from the New South Wales Railways. With the introduction of the locomotives came a brand new numbering and classification system. The Commissioners office set about defining a system that gave each locomotive a unique number preceded by a letter that identified its wheel arrangement. Where more than one type of locomotive had an identical wheel arrangement a suffix letter was added; none for the first locomotive class; "A" for the second; "B" for the third and so forth. When painted on each locomotive, the suffix was done as a half size capital letter with primary classification letter and locomotive number both being done full size. Details of the class versus wheel arrangement are shown in the table below.
In true Commonwealth Railways style when the "C" class locomotives arrived in the 1930's the system got modified so that the "C" allocation became a new class of 4-6-0 rather than calling the new locomotives the "GB" class as the system required. There seems to be some confusion about when it was actually implemented but it appears that the classification system existed as talked about as early as 1912 and was used for all "new" standard gauge locomotives from January 1914, but existing narrow gauge locomotives did not get recoded until about 1917. Locomotives in the "D" class were never. recoded from their old NSW road numbers.
| Class | Type | Wheel arrangement |
|---|---|---|
| A | 0-4-0 | OO |
| B | 0-6-0 | OOO |
| C | 0-8-0 | OOOO |
| D | 4-4-0 | ooOO |
| E | 4-4-2 | ooOOoo |
| F | 2-6-0 | oOOO |
| G | 4-6-0 | ooOOO |
| H | 4-6-2 | ooOOOo |
| J | 4-6-4 | ooOOOoo |
| K | 2-8-0 | oOOOO |
| M | 4-8-0 | ooOOOO |
| All locomotives are classified according to the wheel arrangement as shown. Narrow gauge locomotives were prefix with the letter "N" | ||
One of the stranger features of the way the Commonwealth Railways worked was how locomotives could be officially written off the books yet still be retained awaiting scrapping. This lead to members of the "D" class being officially condemned, yet still in service twenty years latter as emergency shunters.
To understand how this came about it is necessary to appreciate the funding arrangements under which the Commonwealth Railways operated. When any new capital item of rollingstock was required, it was necessary to go directly to Parliament and obtain a funding allocation, a lengthy task very open to political manipulation, delays and on occassion out right refusal. As a direct result, the Commissioners and staff became experts at reusing everything. This was very evident in the rollingstock field were vehicles were rebuilt several times during their working life as traffic requirements changed. Many of the original flat wagon purchased in 1913 was still in service in the late 1990s.
No formal coding system seemed to exist in the diesel era. The classification seems to have been based around who the manufacturer of the locomotive was. Hence "GM" for General Motors, "NSU" for narrow gauge Sulzer etc. Only the "N" prefix to signify narrow gauge seemed to be retained.
