Badische Hauptbahn
Since the Baden Mainline between Mannheim and Heidelberg was built with a broad gauge of 1600 mm and the Main-Neckar line with standard gauge of 1435 mm, additional track had to be built: from Friedrichsfeld to Heidelberg a second line ran next to the line of the Baden State Railway line. From Friedrichsfeld to Mannheim, the Baden State Railway built an additional standard gauge track at its own expense, although it was operated by the Main-Neckar Railway.