As the Environmental Protection Agencys (EPA) Office of Transportation and Air Quality develops its programs to control greenhouse gas (GHG) emissions from light-duty highway vehicles, there is a need to evaluate the costs of technologies likely to be used to meet these standards. EPA contracted with FEV, Inc., to perform this cost analysis through tearing down vehicles, engines, and components, both with and without these technologies, and evaluating, part by part, the observed differences in size, weight, materials, machining steps, and other cost-affecting parameters. Though complex and time-consuming, EPA believes this approach has great potential for determining accurate technology costs, a goal that is of paramount importance in the setting of appropriate GHG standards. EPA tasked ICF International (ICF), an independent third-party contractor, to conduct a peer review of the cost analysis now in progress to assure that this work incorporates the highest quality science.