Ryan Avent points out that "America is forecast to grow by over 100 million people in the next few decades":
The smart critics with whom I’ve debated tend to argue something along the lines of this: in a world in which current transportation planning and pricing weren’t bollixed up, [high-speed rail (HSR)] would make more sense, but given that they are, it doesn’t. With heavy auto subsidies, HSR becomes a boondoggle rather than a savvy investment, and so bollixed is better than bollixed plus HSR. But that’s not actually the choice we face. Amid heavy congestion and with the pressure of 100 million more Americans bearing down on governments, new construction will take place. And so the decision is between bollixed plus HSR and bollixed plus new highways. And on almost every measure, bollixed plus highways is the worse of the two options.