EPA is adopting a comprehensive program to address air pollution from passenger cars and trucks. The final program, known as Tier 3, will establish more stringent vehicle emissions standards and reduce the sulfur content of gasoline, considering the vehicle and its fuel as an integrated system The final Tier 3 standards will reduce concentrations of multiple air pollutants (ambient concentrations of ozone, particulate matter (PM), nitrogen dioxide (NO2), and mobile source air toxics (MSATs)) across the country and help state and local agencies in their efforts to attain and maintain health-based National Ambient Air Quality Standards (NAAQS). This Regulatory Impact Analysis provides technical, economic, and environmental analyses of the new standards. Chapter 1 contains our technical feasibility justification for the final vehicle emission standards, and Chapter 2 contains the estimated costs of the final vehicle standards. In addition to the vehicle emission and gasoline standards, we are adopting an update to the specifications of the emission test fuel with which vehicles demonstrate compliance with emissions standards; our analysis of the emission test fuel parameter changes is found in Chapter 3. Chapters 4 and 5 contain our technical feasibility and cost analyses for the final gasoline sulfur standards, respectively. Chapter 6 describes the health and welfare effects associated with the air pollutants that will be impacted by the rule. Chapter 7 describes our analysis of the emission and air quality impacts of the Tier 3 rule. Our estimates of the program-wide costs, the societal benefits, and the cost per ton of emissions reduced due to the final Tier 3 program are presented in Chapter 8. Chapter 9 contains our analysis of the final rules economic impacts, and Chapter 10 provides the results of our small business final regulatory flexibility analysis.