I agree; it is not the goverment's role, much less is it actually possible for them, to decide whether the needed cuts in carbon emission come from cars going s

I agree; it is not the goverment's role, much less is it actually possible for them, to decide whether the needed cuts in carbon emission come from cars going slower on the roadways, from car buyers favoring hybrid cars or public transportation, from less goods being bought that require carbon to be made, or any of literally a million other options for carbon reduction. They should impose a pigovian tax on carbon, steadily increasing until they have achieved the level of carbon reduction desired, and let the free market sort out the particulars of where the carbon reduction happens.