Why not build the well-documented high-speed gondola system recently profiled in LA Times Magazine ?
Based on images provided by the web site, the gondolas would not fit under highway underpasses, or would interfere with a lane. But building them over underpasses would mean a 3-4-story height because trucks driving on the overpasses have to clear them at least by a yard. This height necessitates huge pylons, extremely difficult and expensive to work on because of the altitude. Also, this system is not intended to be user-skill based. The gondolas are intended to stay on the line, and this vastly increases the complexity and cost of stations.
