They accomplish the same thing as a train, while being more expensive, easier to kill via vendor lock, and more expensive to expand.

They do have a place similar to guided buses, when you need an elevated rail, but have too many hills for steel on steel.

Monorail takes all of the concepts of trains, makes it harder to implement, places a max speed on it, and introduces a thousand more little complexities. Just build trains.

Mono = one
Rail = rail

I would love to ride this.