It seems to me the problem with the footprint model is much the same as the previous model holding "trucks" to a different standard: it's treating size as a goo

It seems to me the problem with the footprint model is much the same as the previous model holding "trucks" to a different standard: it's treating size as a good reason for people to buy less efficient cars. Size is occasionally a good reason. Someone who needs to carry 15 passengers needs a van, and someone with a heavy load to haul needs a truck. The trend in the US, however has been for people who only need cars to drive trucks and large SUVs. Outright telling people what to drive seems like government overreach to me, but there may be another way: adjust the standards so that large vehicles don't get special treatment. Selling too many large vehicles would then hurt a car manufacturer's average and they would be incentivized to stop making such vehicles as appealing for everyday use, e.g. by removing luxury options.