Economics of Fuel Economy Standards
This paper discusses several rationales for the Corporate Average Fuel Economy (CAFE) program, including reduced oil dependence, reduced greenhouse gas emissions, and the possibility that fuel saving benefits from higher standards might exceed added vehicle costs.
Link
http://econpapers.repec.org/scripts/redir.pl?u=http%3A%2F%2Fwww.rff.org%2Fdocuments%2FRFF-DP-03-44.pdf;h=repec:rff:dpaper:dp-03-44