Alice Rivlin and Benjamin Orr are recommending the nation move to a system in which vehicle miles traveled are tolled, with a toll that varies by congestion level. They suggest it be tested in a major metropolitan area first — Washington. What would this look like?

The system might work like this: Vehicles would be fitted with a GPS device to record distance traveled, time and location of travel, and type of vehicle. This data would be sorted into various toll categories, and the device would wirelessly upload the totals to the gas pump when the motorist refueled. The pump would significantly discount the gas tax and add the appropriate road-use fees to the fuel bill. To further protect privacy, only category totals would be communicated to the governing agency via the pump. Tourists and others lacking the transponder would pay the full gas tax. Travel outside the area would not be recorded.

Resources for the Future calculated that the charges under a similar policy for the Washington area would average 9.3 cents per mile. They estimated an 11 percent reduction in VMT, 19 percent less emissions of volatile organic compounds and 17 percent less carbon monoxide. The estimated social welfare benefits (reduced congestion, pollution, accidents, etc.) of this reduction in driving were estimated at the equivalent of $1.1 billion — even before the revenues were disbursed.

There are some Congresspersons out there who seem to like the idea of a VMT tax, so maybe this has a greater than zero chance of being adopted.