In this paper, Greenstone, Sunstein and Ori propose two major steps towards simplifying fuel efficiency standards and refocusing the program on achieving guaranteed emissions reductions at lower cost to automakers. First, they propose targeting greenhouse gas (GHG) emissions directly, without differentiating by vehicle types and sizes, using data to project a given vehicle’s lifetime greenhouse gas emissions. Second they recommend establishing a robust cap-and-trade market to reduce compliance costs for automakers while providing considerably more certainty about the future path of carbon dioxide emissions.