The Integrated Market Penetration and Anticipated Cost of Transportation Technologies model, or IMPACTT, is a spreadsheet model that calculates the effect of advanced-technology vehicles and market penetration on baseline fuel use and emissions. Outputs include estimates of the quantity and value of oil displaced and emissions reduced by advanced-technology vehicles, the quantity of alternative fuels they consume, and the total incremental costs bome by purchasers of advanced-technology vehicles. In the current version of IMPACTT, up to eight fuel or engine technologies applicable to light-duty vehicles can be modeled by using a three-phase approach. First, the vehicle stock and miles traveled by the advanced-technology vehicle are determined. Second, assumptions about efficiency and fuel shares are used to estimate substitution-fuel use and oil displacement. Third, changes in emissions of carbon monoxide, non-methane hydrocarbons, nitrogen oxides, and carbon dioxide are computed.