In Houston, I believe funding is a major issue in getting the light rail lines built. The Red line has been finished since 2004, but no work has been done since. I know the transit authority has been trying to determine the best route for the University corridor line. One route takes it down Richmond Avenue, but a neighborhood on Richmond has gone NIMBY on that plan. The other route is down Westpark.
I think the red line has made a vast improvement to the look and feel of downtown, midtown, and the medical center.
My dad always talks about Houston's plan for monorail way back in the 80s. The mayor back then was looking ahead, unfortunately, it didn't take off.
However, METRO currently has plans for several commuter rail lines that extend out to the suburbs. Let's hope they are a success. Of course, I say we tax gas...let's say $2 a gallon...that'll put butts in those rail cars.
Houston rail plan