While the program is supposed to run July 1 through November 1, The U.S. Department of Transportation has 30 days to set regulations for the program ? including how dealers should crush, shred or otherwise dispose of traded-in clunkers ? after it gets Obama?s signature. Legislators, however, have laid out the basic framework. Here?s how it works:

Clunkers, Defined: You can only trade in drivable vehicles made in the last 25 years that have been continuously insured by the same owner for at least one year leading up to the trade in (so no junkyard finds or used cars bought to ?flip?). Qualifying ?clunkers? will have a fuel economy rating of no more than 18 MPG (combined city and highway ratings, which you can find on fueleconomy.gov).

How Much Cash?: New cars qualify only if they have a sticker price of $45,000 or less. So no Tesla Roadsters  ($109,000), but a Toyota Prius ($22,000) could qualify, depending on your trade-in. And once the $1 billion appropriated for the program runs out (good for an estimated 250,000 vouchers), it?s over unless Congress extends the program.

Passenger Cars: New passenger cars will qualify under the program only if they have a fuel economy of at least 22 MPG. If the new model gets four more miles to the gallon than the old car, you qualify for the $3,500 credit. With a 10 MPG improvement or more, you can qualify for a $4,500 credit.

Trucks and SUVs: For light trucks, SUVs and minivans, the new vehicle has to get at least 18 MPG and can offer as little as a 2 MPG improvement over the old one to qualify for $3,500. With a minimum 5 MPG improvement, you can qualify for $4,500.

5 Important Things to Know

• Your vehicle must be less than 25 years old on the trade-in date
• Only purchase or lease of new vehicles qualify
• Generally, trade-in vehicles must get 18 or less MPG (some very large pick-up trucks and cargo vans have different requirements)
• Trade-in vehicles must be registered and insured continuously for the full year preceding the trade-in
• You don't need a voucher, dealers will apply a credit at purchase

Eligibility Chart