The GTW, an abbreviation of the German for articulated multiple-unit train, is a single-decker regional train. With the first generation of its own articulated multiple unit vehicles, Stadler laid the foundations in 1995 for its current success as a train builder with a comprehensive passenger transport package.

The articulated multiple unit is a low-floor single-decker regional train. The tractive unit is located between the carriages, although the train is still accessible throughout. Depending on their design, the articulated multiple unit trains achieve a maximum speed of 140 km/h. They are available in trainsets of two to four cars, in narrow, standard and broad gauge, as an electric multiple unit (EMU), diesel multiple unit (DMU) or bimodal multiple unit (BMU).

The articulated multiple unit 2/6 developed by it was unveiled in 1995. Stadler received the first orders for articulated multiple unit trains in the form of metre-gauge trains from ASM (formerly BTI) and MOB and in the form of standard-gauge trains from Mittelthurgaubahn – currently Thurbo.