It's not easy to see how the mechanisms actually work, but I suppose it happens because those negotiations are more about power games than actual, rational proc

It's not easy to see how the mechanisms actually work, but I suppose it happens because those negotiations are more about power games than actual, rational processes towards specific goals. The relevant emission regulations are described in http://en.wikipedia.org/wiki/Corporate_Average_Fuel_Economy http://en.wikipedia.org/wiki/Corporate_Average_Fuel_Economy "CAFE has separate standards for "passenger cars" and "light trucks", despite the majority of "light trucks" actually being used as passenger cars. The market share of "light trucks" grew steadily from 9.7% in 1979 to 47% in 2001 and remained in 50% numbers up to 2011." Thus, the very legislation designed to reduce emissions has resulted in Americans buying bigger and bigger vehicles. From Europe, the rationale for this legislation is hard to understand.