This kind of "average" nonsense in the form of CAFE[1] standards is why we have endless SUVs and crossovers on the road now. I expect that this will lead to similar unintended consequences.

[1] https://en.wikipedia.org/wiki/Corporate_average_fuel_economy

> A complicated 2011 mathematical formula was replaced starting in 2012 with a simpler inverse-linear formula with cutoff values.[10] CAFE footprint requirements are set up such that a vehicle with a larger footprint has a lower fuel economy requirement than a vehicle with a smaller footprint.