The original double - track line presented an obstacle to high - speed long - distance passenger transport .
Line followed the western edge of a steep ridge called the Isteiner Klotz and can only be operated at comparatively low speed due to the numerous curves in this area .
The original double - track line presented an obstacle to high - speed long - distance passenger transport because it followed the western edge of a steep ridge called the Isteiner Klotz and can only be operated at comparatively low speed due to the numerous curves in this area .