In the United States, private automobiles form the backbone of our transportation systems, providing quick convenient transportation to various destinations, consuming vast quantities of processed petroleum, mostly from other countries, while producing large amounts of problematic air pollution.  The Corporate Average Fuel Economy (CAFE) legislation mandates increases in fuel efficiency for new automobiles, in an attempt to reduce these harmful problems.  Unfortunately, the indirectness of the approach hinders its effectiveness and produces a number of unintended side effects, which introduce harms of their own, making this a poor choice as a method of reducing dependence on foreign oil and the ecological and health damage from its consumption.

Any barrier to free exchange is politically difficult to implement, even when the exchange carries with it a great deal of negative externality.  Thus, the direct approach, to limit fuel production or to tax it more heavily, has been avoided as motorists, fuel producers, and dependent industries all resist such changes.  Regulating fuel efficiency in new cars, on the other hand, is a less direct exercise of power, which affects people only as they purchase new cars, and has a smaller impact on the relevant political constituencies than the gas tax does.

The CAFE standards produce a variety of secondary effects in addition to its directly legislated effects, which make it doubtful that it is worth the costs it imposes.  Prior CAFE regulations resulted in smaller lighter vehicles which were less safe for their drivers in the event of an accident, it seems likely that new efforts for fuel efficiency would result in similar choices being made, further increasing the safety risks.  The proposed changes would result in a reduced range of options for automobile manufacturers to producers, and consumers to purchase.  It would also force manufacturers to focus research efforts on increasing fuel efficiency, rather than other potentially valuable areas, such as designing engines for alternative fuels or increasing safety and maneuverability.  

Additionally, a number of effects of increasing fuel efficiency act to offset benefits gained by implementing more stringent standards.  Increasing fuel efficiency reduces the costs of driving born by the driver and will likely increase the number of miles driven, cutting into the reduction in fuel consumption.  Current polution regulations set limits based on the number of miles driven, rather than the gallons of fuel consumed.  Furthermore, the delay introduced into this process by introducing these standards for new cars only means a very gradual increase in average fuel economy for the fleet of vehicles.  

Weighing the effectiveness of the proposal and the costs it would entail, it seems to be a poor investment of time, attention, and energy, further a superior alternative exists.  This indirect approach to the goal of reducing oil consumption and dependence produces a range of side effects, and compensates for itself in other ways that make it unlikely to work.  Raising the gas tax, while politically difficult, would be much more effective in reaching the desired goals.  The gas tax could also be targeted geographically to the areas where air pollution is likely to do the most harm.  Local governments in areas with high population densities ought to implement their own fuel taxes, and an entry fee for vehicles entering from areas that do not have the environmentally oriented gas taxes.  Additionally, reducing dependence on private automobiles by working to improve public transportation and increase the density of development has great potential to reduce both oil dependence and the negative externalities of fuel use.