Monorails don't seem to get built in cold climates. Could a monorail even run during an ice storm? And how would you heat the thing up there in the wind. I've also been on el platforms in Chicago in winter, and, believe me, many people up there would much rather have a dank but warm subway platform to stand on.
So, this eliminates many great cities north of, say, Atlanta or thereabouts. That sure doesn't leave a lot of cities in the world to get high production and economies of scale going in the monorail industry. Yeah, they look and sound great, but, like the concorde, their shortcomings continue to cripple them. (The concorde, due to sonic booms, only flew a very few trans-oceanic flights, thus making them a novelty instead of a worldwide workforce of a jet.)
