Cars are going to get smaller anyway, because the price of gasoline is going up.
If you think $4/gallon was a lot, wait til the dollar takes a dip, and oil is traded in Euros.
You will still be able to drive whatever you want, all of today's vehicles will still be available on the used car market, you can still drive a 76 Eldorado with the 500 cubic inch engine if you want.
But at $10/gallon, most people will opt for a smaller car that gets better mileage.
(Opening a niche for the electric muscle car).

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“ The subjects of every state ought to contribute towards the support of the government, as nearly as possible, in proportion to their respective abilities; that is, in proportion to the revenue which they respectively enjoy under the protection of the state.”

Adam Smith , The Wealth of Nations 1776

"We have always known that heedless self-interest was bad morals; we know now that it is bad economics"
FDR's second Inaugural Address