At the beginning of the 1890s, express trains were still transported on the Gotthard railway in two separate ways. In the lowlands from Lucerne to Erstfeld the trains were pulled by light tank locomotives and in the mountains freight locomotives took over. In order to accelerate these trains, new locomotives were needed that combined sufficient tractive power with a higher maximum speed, thus making locomotive changes and double heading superfluous. The requirements were to transport an express train of 140 tonnes alone on the mountain and 250 tonnes on the flat.
In order to enable sufficient tractive effort and, at the same time, good curve running, the locomotive was given three coupled axles and a leading bogie, which made it the first locomotive of this wheel arrangement in Switzerland. A driving wheel diameter of 1,610 mm represented a good compromise for the required performance. For smoother running, coil springs were used instead of leaf springs, which were later replaced with leaf springs.
The first prototype with the number 201 was built with a three-cylinder compound engine. In order to develop a higher tractive force on the mountain, the low-pressure cylinders could be operated permanently with live steam. In the 202, a four-cylinder compound engine according to De Glehn was used, which also worked with the compound effect on the mountain.
For the production of the 28 series machines, the arrangement with four cylinders was chosen because it ran more smoothly and was more economical on the mountain route. Compared to the 202, the cylinders were enlarged while the boiler pressure was increased from 14 to 15 bars. The high-pressure cylinders acted on the first and the low-pressure cylinders on the second coupled axle. A slightly smaller boiler was installed in the last six locomotives from number 225 onwards. These locomotives were later retrofitted with a superheater.
The locomotives could pull a 320-tonne express train on the flat at 50 km/h. A load of 140 tonnes was initially planned for the ascent at 40 km/h, which was later reduced to 120 tonnes to reduce fuel consumption. Likewise, the tender was expanded from a water capacity of 14.4 to 17 cubic meters. When the Gotthard Railway was nationalized in 1909, the SBB gave the locomotives the numbers 901 to 930. After the line was electrified in 1920 and these locomotives were slower than later type A 3/5 locomotives, they were retired between 1923 and 1926.