A few comments:
I believe that some things are obvious.
I also believe there is always room for elevated transportation.
I must also respectfully disagree that contruction and maintenance of roadways is a "well developed technology". Righit now, roadbeds have reached their "level of incompetence", as the Peter Principle states. They cannot be improved in any economical manner since they come from a flawed design basis. Worse yet, they continue to deteriorate at an alarming and increasing rate. That last fact alone is very frightening when one considers the already past trillion dollar damage to our national physical plant. There is no way that we can fix that since we can't end the war on drugs (over one trillon dollars to date), the wars overseas (another trillion?) or our national debt (don't even ask
).
Only maglev will economically solve a part of the necessary infrastructure repair/replacement.