I first saw it in a comic book. Roger Leloup, who drew most of the fancy planes and cars in Tintin, had his own series called Yoko Tsuno, and he used the Wuppertal suspended rail for a minor plot point in one album ("Odin's fire"). In order to have an excuse to draw it, most likely. His love for drawing cool technology shines through.

Half-asleep, expecting normal train scenery, and then bam: suspended train casually gliding over a river