At the request of the Northeast Ozone Transport Commission (OTC), EPA is announcing today its final determination that reduction of new motor vehicle emissions throughout the Northeast Ozone Transport Region (OTR) is necessary to mitigate the effects of air pollution transport and to bring nonattainment areas in the OTR into attainment (including maintenance) of the national ambient air quality standard for tropospheric ozone (smog). This will assist OTR states in their efforts to reduce ozone pollution to the level necessary to protect public health. EPA today approves the recommendation of the OTC and promulgates a rule under sections 184 and 110 of the Clean Air Act (the Act) that requires emission reductions from new motor vehicles in the OTR equivalent to the reductions that would be achieved by the OTC Low Emission Vehicle (OTC LEV) program. States would be relieved of their obligations under this requirement if EPA were to find that all automakers had opted into an acceptable LEV-equivalent new motor vehicle program. EPA believes that such a program, which would be far better than OTC LEV, could be agreed upon and adopted in the near future. States' obligations under this requirement could also be met by a state's revision of its state implementation plan to include the OTC LEV program. Today's action gives states additional flexibility by also allowing a state the option of adopting a set of measures that would achieve certain emission reductions needed to prevent the state's adverse pollutant transport impacts. EPA is also promulgating a final rule today determining ``model year'' for purposes of section 177 and part A of title II of the Act, as that term is applied to on-highway motor vehicles.