For countless travellers, the slam of a compartment door, the corridor’s patterned light, and the steady ride of an S type carriage defined the experience of railway travel in New South Wales for over half a century, from the 1930s to the end of the 1980s.

Built by Clyde Engineering between 1937 and 1939, the fleet were the first steel-bodied carriages to be used on the network and comprised thirty-five first-class BS vehicles and eighty-six second-class FS vehicles. A BS carriage seated forty-two people in roomier first-class compartments, while an FS could carry sixty-four.

From the outset, the 'S' type cars were intended to be used on almost any service for which they could be called upon from country day trains to the overnight Limited expresses to Albury and Brisbane. Combined with the timber 72ft 6in mainline cars, they formed the backbone of country express services in NSW. Their compartment layout offered privacy, while the steel construction reduced maintenance compared with earlier timber designs, while also offering significant safety improvements.

The introduction of the 'S' cars allowed for large numbers of ageing "dogbox" cars to be cascaded down to branchline service or released for rebuilding into more modern 'R' and 'L' type cars.