A little-noted provision of President Obama’s highway funding proposal would lift the federal prohibition against states imposing new tolls on existing interstate highways. The GROW AMERICA Act would eliminate restrictions held in place since the creation of the Federal Interstate System, according to a summary of the plan’s provisions, allowing states that receive permission from the Secretary of Transportation to toll existing Interstate highways “in order to make improvements or to manage congestion.” Since its creation in 1956, interstates have been funded primarily through fuel taxes, with tolls banned on all sections of highway built after that date, according to...