In 1893, the Prussian state railways introduced the first modern fast trains (in German "D-Zug") using the new steam locomotive (S2/PKP class Pd1) which could reach a speed of . The trains also included 4-axle bogie coaches with compartments and side corridor and covered gangways (Corridor trains). One such fast train route was that from Berlin to Bromberg and Danzig. In 1898, the first locomotive using superheated steam in the world, designed by Wilhelm Schmidt, was produced by the Vulkan company in Stettin for Prussian state railways (KPEV "Hannover 74" S4). This opened a new age of steam locomotive development. Construction of the prototypes of superheated steam locomotive classes by Robert Garbe started in 1902. These were: S4 (PKP class Pd2) for fast trains, P6 (PKP class Oi1) per passenger trains and G8 (PKP class Tp3) for goods trains.