A simple measurement of mpg and emissions should be the only criteria, and let the market decide how to meet it.
Or, simpler yet (as previously discussed)--don't legislate by technical edict (e.g. buy a car with a certain MPG or grams/mile emissions gets a tax credit) but just tax fuel at a higher rate. This does three things:
1) Gives technology free reign to solve the problem in the best way (lean burn? Hybrid? Injection of HOOH? Let the scientists and engineers compete and come up with the best solution for each vehicle type and use. They will be different)
2) Gets the most efficient cars in the driveways of the people who do the most driving. This is huge. It is a net environmental/energy
loser to give a tax credit which encourages a 100 mile-per-week driver to trade in an 18 MPG car for a Prius. If anything, the government should figure out a way give him a tax incentive to keep driving that car as long as possible. On the other hand, getting a 150 mile-per-day driver into a fuel efficient car helps reduce those uncompensated externalities a lot.
3) Encourages fuel savings (what we say we are trying to achieve) rather than a particular means of fuel savings (hybrid vehicles, lean burn, hamster power, etc). Remember all the activity when gasoline was above $4 per gallon--activity on Craig's list and in offices to set up car pools, more public transportation ridership, etc. We had a real decrease in automobile miles driven for the first time in years. No tax credit for hybrid vehicles is going to accomplish that.
Also, as ERD-50 has pointed out, a steadily-increasing fuel tax (with a planned progression over many years) gives the public and the automotive engineers a clear picture of what lies ahead regarding fuel costs. This would provide a solid basis for making engineering and design changes and investments that is lacking today, and would serve as another incentive for technological improvement. This would be much more effective than the arbitrary and slowly increasing CAFE standards.
I like taxes--that I can avoid. I can drive less and avoid paying this tax.
Again, I'm not saying that we should necessarily have a fuel tax. But, all taxes modify behavior in some way.
If we, as a society, believe that fuel use has uncompensated externalities that are truly worth the cost of addressing (cost= more lives lost in road accidents in smaller cars, reduced economic activity due to higher transportation costs, etc), then a revenue-neutral fuel tax probably makes much more sense than these rifle-shot technically-focused approaches. Congress should concentrate on the big-picture policy issues and get out of engineering.
Apologies if I sound like a broken record on this issue. But if they keep doing dumb things, it's hard not to chime in.
