The earliest cars to operate on narrow gauge were four wheel vehicles that were later followed by 6 wheel "Cleminson" type radial underframe cars. As new cars were introduced the older cars were converted to post office vans and workmans cars, many of which lasted until the end of South Australian Railway narrow gauge. The most probable reason for the lack of new passenger rollingstock on the narrow gauge was the gradual reduction in operating miles caused by conversion of narrow gauge lines to broad gauge and the transfer of the North Australia and Central Australia Railway to the Commonwealth.
The South Australian Railway did not use a classification system for its narrow gauge cars, instead issuing each car with the next unused road number. During 1953 a partial classification system was undertaken, mainly for seat reservations, similar to that used with broad gauge cars. Similar types of cars would all be allocated a sequential number in the same series.
Cars built prior to 1882 had a simple radiused roof, after this Mansard roofs were fitted to all new cars except for Alberga, Coonatto and Nilpena which all had elliptical roof. The Mansard roof cars were known as "American type", carriages. End platforms and ground loading steps were fitted to all cars as the only raised platforms on the narrow gauge system was at "break of gauge" stations.
All the passenger carriages in service on trains working between Terowie and Broken Hill had a section of the canopy at each end removed in 1968. The section is on one side, and is that side which faces south in the Peterborough Station yard. It was necessary because of the new Peterborough Station platform being used by narrow gauge trains. The platform is so high that had the cars not been altered, only midgets would have avoided bumping their heads on the canopy as they entered the cars.
All the 31 foot 6 inch cars, sometimes known as Short Toms, have a similar appearance, representing several variations of the same theme. The main external difference between the various type is the arrangement of the windows and the location of water tanks if present. The bogies of all cars are of similar appearance, but the wheelbase varies, being 4 foot 6 inch for early cars and 5 foot for later built vehicles.
Built between 1883 and 1895, the these cars were the first narrow gauge cars of the South Australian Railway to be built with a "Mansard" type roof. They were referred to by the railways as "American type" carriages.
The first of these cars did not have any lavatories and were divided into three compartments, one first class and two second. Longitudinal seats were fitted to the first and second class compartment located either end, with the central second class compartment being fitted with transverse seats for use by ladies or smokers. Capacity was approximately 14 first and 25 second class passengers.
A total of 36 cars (Nos. 4, 43 to 50, 65 to 75, 86 to 90, 94, 95, 115 to 118, 124, 125, 137, 138 to 143) were constructed. The first two cars, Nos 4 and 43, only had two compartments, both fitted with longitudinal seating. Between 1908 and 1913, all these cars were fitted with electric light in place of oil, Westinghouse air brakes and through communication from one car to another on the end platforms
The 50 foot cars formed the backbone of the main-line service from Terowie to Broken Hill, and the South East line from Wolseley to Mount Gambier. These cars were known as Long Toms.
A total of 34 cars were built between 1911 and 1920 at the Islington Workshops, their original numbers being 177 to 197, 207 and 208, 212 and 222. As originally built all cars had end platforms and ground loading steps, Mansard type roofs, the interiors were divided into two compartments with two lavatories between them in the centre of the car. Seats were arranged longitudinally, each seat being divided into three parts by arm rests for a total capacity to 60 passengers. All cars were originally issued as second class.