In May 2009, the U.S. announced plans to increase the Nat. Highway Traffic Safety Admin. (NHTSA) corp. average fuel econ. (CAFE) standards and establish the EPA greenhouse gas emissions standards for vehicles. NHTSA redesigned CAFE standards for light trucks for model years 2008-11. Experts raised questions about the rigor of the computer modeling NHTSA used to develop these standards. This report reviewed: (1) the design of NHTSA and EPA's standards; (2) how they are collaborating to set these standards; (3) improvements compared to a previous rulemaking NHTSA made to the modeling; and (4) the extent to which NHTSA analyzed the effects of past light truck standards and the accuracy of data used to set them. Charts and tables.