Car sales in Germany jumped an astonishing 40 percent in March, thanks in large part to a "cash for clunkers" program in which the government gave those handing over old-model cars roughly $5,000 toward the purchase of newer, more fuel-efficient vehicles. Lawmakers in the United States have crafted similar proposals, hoping both to provide a boost to the U.S. auto industry and to spur sales of environmentally friendlier cars. But even the best of these proposals is not likely to provide the punch of the German initiative.

A bill co-sponsored by Sens. Dianne Feinstein, D-Calif., Charles E. Schumer, D-N.Y., and Susan Collins, R-Maine, offers the most sensible approach. Buyers are eligible for vouchers worth $2,500 to $4,500 toward the purchase of a new car if they turn in older vehicles that get less than 18 miles to the gallon. The older vehicles would be junked and turned into scrap. The new car must have a sticker price of less than $45,000 and surpass fuel economy standards by 25 percent. Buyers may also apply the vouchers to fuel-efficient used cars manufactured after 2003. Vouchers could also be used for participating in public transportation programs. A similar proposal in the House provides credits only for vehicles made or assembled in North America; such a provision is problematic because it could violate free-trade agreements.

But would even a perfectly crafted program trigger the kind of spending spree witnessed in Germany? Unlikely, largely because of simple economics and human nature. In 1999, the German government began to gradually impose an additional tax on each gallon of gas beyond the existing tax; today, the additional tax stands at 50 cents, and high gas prices push consumers toward fuel-efficient cars or public transportation even without additional incentives. Yet the Germans did not stop there. The country announced at the start of this year that it would implement in July a new tax based on carbon dioxide emissions; the larger the car and the greater its emissions, the higher the tax. No wonder, then, that Germans flocked to take advantage of the cash-for-clunkers deal before driving becomes even more expensive.

The psychology and politics are completely different in the United States, where it is still relatively cheap to drive. Gas prices here briefly flirted with the $5-per-gallon mark in some parts of the country last summer but have again stabilized around $2 per gallon. Talk of any new taxes -- even a gradual pennies-to-the-gallon gas tax -- is anathema to most politicians on both the left and right.

Some consumers will buy more fuel-efficient vehicles simply for the environmental benefits, but most of us need either bigger savings or a bigger hammer in the form of taxes to turn us away from our cherished sport-utility vehicles. A cash-for-clunkers program would be a good first step toward revamping the nation's fleet, but without other incentives and other pressures such an initiative is not apt to have a great impact in the United States.

This editorial appeared in The Washingon Post.

(April 13, 2009)