The “Cash-for-Clunkers” program–officially the Car Allowance Rebate System (CARS)–was not designed by the US Department of Transportation (DOT) only as an environmental program.

Some environmental impact was certain given the requirement that newly purchased vehicles be more fuel efficient than trade-ins, but the program is primarily a way to boost auto sales. CARS has met or surpassed expectations on both accounts.

People are rushing to trade in their “clunkers:” the initial $1 billion dollars in funding was given out quickly, prompting congress to push an additional $2 billion into the program. As of August 13th, 338,659 transactions have been submitted.

This is great news for the auto industry, which had been struggling mightily to cope with the recession (in case you hadn’t noticed…).The trend seems to be towards trading in light trucks and buying sedans, which can be taken as a good sign for the programs green credentials as well as shifts in American consumers tastes on cars.

The top 10 trade-in models (as of August 12), are all light trucks: 6 SUVs, 2 mini-vans, and 2 pick-ups. Of the top 10 new cars bought through the program, on the other hand, 8 are sedans.

Here’s a list of the top 10 trade-ins and new vehicles under CARS, provided by the Guardian:

Top 10 Trade-in Vehicles

1. Ford Explorer 4WD

2. Ford F150 Pickup 2WD

3. Jeep Grand Cherokee 4WD

4. Jeep Cherokee 4WD

5. Dodge Caravan/Grand Caravan 2WD

6. Ford Explorer 2WD

7. Chevrolet Blazer 4WD

8. Ford F150 Pickup 4WD

9. Chevrolet C1500 Pickup 2WD

10. Ford Windstar FWD Van

Top 10 New Vehicles Purchased

1. Toyota Corolla

2. Ford Focus FWD

3. Honda Civic

4. Toyota Prius

5. Toyota Camry

6. Hyundai Elantra

7. Ford Escape FWD SUV

8. Dodge Caliber

9. Honda Fit

10. Chevrolet Cobalt

The exact environmental impact of this program is very hard to calculate. For example, the clunkers  being traded-in may have been lightly used while the new cars are driven more miles, eliminating their fuel efficiency advantage. The existence of so many fuel efficient models on the new vehicles list, and so many inefficient models on the trade-ins list is a good sign, though.