The Wall Street Journal’s Ana Campoy reports:

As politicians debate how to break the nation’s addiction to foreign oil and curb its global-warming emissions, laypeople are already setting an example: They’re cutting back on driving.

That’s not just because they were shocked into conserving when gasoline prices surpassed $4 a gallon earlier this year, points out a new study by the Brookings Institution titled “The Road… Less Traveled.”

U.S. drivers began pushing the brakes four years ago — well before gas prices began shooting up. But it was 2007 when, for the first time, the number of miles traveled in the U.S. actually fell compared with the prior year.

That’s because, at this point, there are relatively few people eligible to drive who aren’t doing so already. The growing use of public transit and the sprouting of shopping centers in residential areas are also helping, the study says. These are changes the authors don’t expect will be reversed in coming years, even if gas prices keep falling.

The drop in miles driven will likely force the massive reorganization of transportation policy that experts say is badly needed, but that policy makers have so far skirted.

For starters, Congress will have to figure out how to make up for the shortfall in gasoline - tax revenue, which is used to fund transportation projects, as people use less of the fuel. Short-term, Brookings says, lawmakers should raise gas taxes, and while they’re at it, they should index them to inflation so that they rise along with overall prices. In the long-term, the study suggests a carbon tax. [WSJ Environmental Capital]