The Paving Of America

Bradford Plumer explains highway bias in transportation policy:

Under current law, the federal government usually covers about 80-90 percent of the costs for a new highway project, compared with only 50 percent of the costs for a transit system. Local communities have to pick up most of the rest of the tab for public transportation, with state governments chipping in what's left. Since doing that usually requires raising property taxes, most local governments just prefer to build highways.