Under the name GTW, which stands for “Gelenktriebwagen” (articulated railcar), Stadler offered a total of four generations of modular railcars. This arose from the requirement of several railways that were looking for light and equally inexpensive vehicles that could be used in various conditions.
The central component is a two-axle power module, which contains either a diesel-electric unit or the necessary equipment for electrical operation under direct or alternating current. Multi-system variants were also available. At least one two-axle part with a passenger compartment is connected to it on both sides. Different lengths of the car bodies were available and three-part variants were also built.
Since the vehicles were ordered by customers from different countries, they were built with different gauges and in meter gauge, standard gauge and Iberian broad gauge. From the second generation onwards, the round vehicle fronts were used, which became Stadler's trademark. From the third generation onwards, mass-produced components were increasingly used, making production and maintenance cheaper. Likewise, the diesel variants now used two smaller six-cylinder engines instead of a large V12.
