Transportation conformity is a mechanism to ensure that federal funding and approval are given to those transportation activities that are consistent with air quality goals as contained in the State Implementation Plans (SIPs). Once an area reaches attainment, the SIPs are amended to include a 10-year maintenance plan. OKI is the metropolitan planning organization (MPO) for the Greater Cincinnati/Northern Kentucky area responsible for transportation planning and air quality conformity. The latest regional emissions and air quality conformity analysis was completed in November 2022 for the amended FY 2021-2024 TIP and OKI 2050 Metropolitan Transportation Plan .
On June 9, 2022, the U.S. Environmental Protection Agency (EPA) found that the Cincinnati, Ohio area had attained the 2015 ozone National Ambient Air Quality Standard (NAAQS) and redesignated the Ohio portion of the area to attainment. This area includes the Ohio counties of Butler, Clermont, Hamilton, and Warren. EPA also approved Ohio’s motor vehicle emission budgets and maintenance plan. On October 7, 2022, EPA determined that the Kentucky portion of the area failed to attain the NAAQS by the attainment date. Nonattainment and maintenance areas must demonstrate transportation conformity. Transportation conformity is a mechanism to ensure that federal funding and approval are given to those transportation activities that are consistent with air quality goals as contained in the State Implementation Plans (SIPs). OKI is responsible for the air quality conformity determination for the region’s Transportation Plan and Transportation Improvement Program.
In February 2018, the U.S. Court of Appeals for the D.C. Circuit issued a decision in South Coast Air Quality Management District v. EPA. The decision impacts the Kentucky portion of the Cincinnati area that was formerly nonattainment under the 1997 ozone standard but is now in attainment for all other standards (Figure 3). This “orphan area” includes the more rural southern tier of Boone, Campbell, and Kenton counties. This area has not been subject to conformity since the 1997 ozone standard was vacated. In June 2018, OKI redemonstrated conformity with the 1997 ozone standard. U.S. DOT approval of the conformity determination occurred on September 6, 2018. Per recent guidance, OKI will continue to qualitatively demonstrate Kentucky’s conformity with the 1997 standards for future MTP and TIP amendments.