Practical considerations have, until recently, prevented serious discussion of a cap and trade system for car driving.  This is unfortunate.  No other alternative so radically transforms the perception of driving for car owners.  I’m a big supporter of increasing the gas tax, but, in my opinion, the gas tax is still a crude form of behavior modification whose primary advantage is its simplicity (which is not an insignificant consideration).  My primary complaint about a gas tax is this: as long as drivers are willing to allocate more of their personal income to driving, a gas tax doesn’t fundamentally change behavior.  Drivers are still able to earn their way out of the penalty for driving.  Toll roads have more similarities to cap and trade than a gas tax, because of the ability to limit the amount of available road space.  Toll roads, however, only work on highways, and don’t provide any incentive for people to limit their car use.  Car owners, of course, are free to tax themselves through the voluntary purchase offsets to match the carbon output from their driving.  But my suspicion is that the current purchasers of such offsets are already a fairly committed bunch.  They’ve already made efforts to reduce their driving or have switched to more fuel efficient vehicles.  The real culprits on the road are immune to such voluntary measures.

Driving is the only form of long haul transportation that isn’t subject to the unsympathetic whims of the market.  The market for airline travel is the perfect counterpoint to our dysfunctional attitude toward driving.  When it comes to driving, we are lemmings, impervious to insults to our dignity and threats to our pocketbooks. Yet, as air travelers, we are sophisticated consumers, acutely aware of daily price changes and bargains.  We search for the best deals, access all available information, and play competitors against one another, and the result is a complex sorting of price sensitivities that keeps the airlines on their toes (and on the brink of insolvency).  The bottom line is: if the price is too high, we don’t fly.  And while air travel might look like simply a private market at work, it is really a form of cap and trade, with the government indirectly regulating the capacity of the system through gates, air traffic restrictions and a range of regulations that serve as significant obstacles for new entrants.

The practical barriers to tracking how much we drive are slowly disappearing.  Oregon recently completed a pilot program to substitute a mileage tax for the gas tax, and installed devices in participating cars that tracked mileage.  The devices also included GPS capabilities for subtracting out-of-state miles for the tax calculation.  Many new cars are already GPS-enabled, and automakers are likely to make the technology standard on all vehicles in the future.  Cruder measures, such as limits on vehicle licenses, are also available to implement the system.  With advances in technology, the only obstacles are once again political.

The problems associated with driving a car are the result of an age old conundrum known as the tragedy of the commons, in which individuals, absent any restrictions or cost burden, will overuse a public resource to the point where it ceases to be of benefit to anyone.  Relying on the market to allocate the precious resources of "the commons" is as old as the puzzle itself.  Yet, we ignore this wisdom and continue to allow people to overuse their driving privileges.  It's time to turn drivers into consumers.  It's time to let the market take over our roads.