I disagree, because robotic transportation is going to make public transportation obsolete long before the debt acquired is paid off.<p>And by then, robotic construction and material will have advanced so much that it will be much cheaper to build underground in the future than it is now.<p>But underground is definitely the way to go for transportation, even in earthquake country.  The surface should be quiet and safe, our streets converted to bike paths and gardens.<p>So lets at least make sure that underground construction could also accommodate vehicles other than trains.  Because all that track will eventually be ripped out when we are liberated from the tranny of the train schedule.