The federal government provides about $20 billion a year in grants to states for highways; most of the money is raised through taxes on motor fuels. States, in financing their road-building programs, also rely heavily on motor fuel taxes and on fees paid by highway users. But these revenues are insufficient. This study reviews several approaches to augment traditional sources of funding for highways. The analysis covers changes in rules governing federal aid, state infrastructure banks, federal credit assistance, and private-sector financing of roads. Charts and tables.