Washington Post: Should you have to pay to drive on the Capital Beltway — and on Interstate 270, the George Washington Memorial Parkway and all the bridges that cross the Potomac? Many economists would say yes. The Bush administration would agree. A federally funded study completed last week lays out how much revenue such a tolling system would generate and how much it could reduce traffic congestion. But if you don’t like the idea, don’t fire off any angry e-mails just yet. "Road …