The United States Environmental Protection Agency (EPA) is approving through ``direct final'' procedure, a March 13, 1998, request from Ohio, for a State Implementation Plan (SIP) maintenance plan revision for the Columbus ozone maintenance area (Franklin, Delaware and Licking Counties). The maintenance plan revision establishes a new maintenance year of 2010 for the area and a new transportation conformity mobile source emissions budget for the year 2010. The 2010 emissions budget projections incorporate future emission reductions from area and point sources. The newly established 2010 emissions projections determine the area's safety margins for Oxides of Nitrogen (NO<INF>X</INF>) and Volatile Organic Compounds (VOCs). Also being approved is the State's request that a portion of the safety margins be allocated to the area's 2010 mobile source emissions budget for transportation conformity purposes. The area's safety margin is defined as the difference between the attainment inventory level (the Columbus area's attainment inventory year is 1990) of the total emissions and the projected levels of the total emissions in the final year of the maintenance plan (as established for Columbus in this rule to be 2010).