Cog railway electric locomotive (similar to series E 69) of the Sonnblick Railway. Cog railways radiate a unique fascination with their combination of mountain scenery and bold track layouts, featuring numerous bridges and tunnels. The train's movement is facilitated by a cogwheel engaging with a rack rail located in the middle of the track, as the usual friction between wheel and rail is insufficient for the steep gradients. In cog railways of the so-called mixed system, where friction tracks alternate with rack sections depending on the gradient, the pulling force is exerted by the same machine. In the Alps, there are particularly many private cog railways that are very popular among tourists from all over the world.