FrogDesign proposed cable gondolas to solve Austin's mass transit problem[1]. With the hills and lakes/rivers in the area, it's a plausible solution (cheaper than a subway, anyway). The only hitch I see is how to air-condition the cars -- I wouldn't want to be in an enclosed glass box on one of our 110F days without it.
Interesting that they compare the cost of roadways to the cost of light rail/subway, but don't mention what the potential cost-per-mile of a gondola system would be.
[1] http://www.theatlanticcities.com/commute/2012/11/forget-subw...