Secretary of Transportation Ray LaHood makes this point in his blog:
"But as the Secretary of Transportation, let me be clear: there is no amount of money that could build enough capacity on our highways and at airports to keep up with our expected population growth in coming decades. America’s population will grow by 70 million in the next 25 years and 100 million in the next 40 years. Adding capacity to an interstate highway in the congested Northeast would cost more than $40 million per mile and cause enormous traffic backups, assuming we even had the space. "
For sake of future affordability we need to rethink transportation.
https://fastlane.dot.gov/2011/02/high-speed-rail-the-future-we-cannot-afford-to-leave-behind.htmloldId.20110216083602463