It’s obviously frustrating that the final version of the fuel economy provision wending its way through congress is probably going to preserve the distinction between cars and trucks (including SUVs). There’s really no good justification, at all, for doing that. It’s weird, too, since many opponents of fuel economy standards cite the danger involved in making cars smaller. To the extent that that’s true, this distinction should have a larger size impact on small cars than on trucks, making roads more dangerous. But it’s not really true.
Anyway, the main point is that if we priced carbon, through a tax or a cap-and-trade system, none of this would matter. Driving a huge SUV everywhere would become as dumb a decision on a personal, financial level as it currently is on a global, climatic level.