It's certainly not a new idea - what's new is the current bipartisan Senate bill, cutely abbreviated as the BRIDGE Act, seeded with $10 billion of federal funds that would attract funds from the private sector to be loaned to worthy projects.
Nov 17, 2013 The Hill's Transportation and Infrastructure Blog
The deficit commission has proposed a 15-cent gas tax, which would fund the Highway Trust Fund for needed infrastructure projects as opposed to deficit reduction. Brooking's Robert Puentes explains why it was included.
Dec 14, 2010 The New Republic