This one seems to work... surprisingly well, considering how bonkers it is: https://en.wikipedia.org/wiki/Wuppertal_Schwebebahn

I've always wondered why they've been so generally unsuccessful; conventional elevated rail works fairly well, and at least in theory they should be much cheaper and less obtrusive.

This. The general concept of "terrible public transport tech disguising as a good & novel idea" has a name: gadgetbahn.