The report has been prepared to provide the Administrator of the EPA with the likely impacts of possible suspension decisions and recommendations to Congress. Impacts considered are those resulting from changes in emission control technology. Included are vehicle cost changes, vehicle fuel economy changes, and unregulated pollutant level changes. For each of the possible decisions and recommendations, the expected direct impacts were determined as a function of time. Five scenarios depict estimated results of five different actions the Administrator may undertake. For each scenario, estimates were made for the type of emission control systems that would be used to meet the standards, the customer first cost of these systems, the fuel economy of a typical car using these control systems and the sulfate emission levels the car would produce. All factors shown are for the 1974 through 1980 model years.