(a) 2015 NAAQS. The 2015 8-hour primary and secondary ozone NAAQS codified at 40 CFR 50.19.

(b) 8-hour ozone design value. The 8-hour ozone concentration calculated according to 40 CFR part 50, appendix P, for the 2008 NAAQS, and 40 CFR part 50, appendix U, for the 2015 NAAQS.

(c) CAA. The Clean Air Act as codified at 42 U.S.C. 7401-7671q (2010).

(d) Designation for a NAAQS. The effective date of the designation for an area for that NAAQS.

(e) Higher classification/lower classification. For purposes of determining whether a classification is higher or lower, classifications under subpart 2 of part D of title I of the CAA are ranked from lowest to highest as follows: Marginal; Moderate; Serious; Severe-15; Severe-17; and Extreme.

(f) 2008 ozone NAAQS means the 2008 8-hour primary and secondary ozone NAAQS codified at 40 CFR 50.15.

(g) Attainment year ozone season shall mean the ozone season immediately preceding a nonattainment area's maximum attainment date.

(h) Initially designated means the first designation that becomes effective for an area for a specific NAAQS and does not include a redesignation to attainment or nonattainment for that specific NAAQS.

(i) Nitrogen Oxides (NO_X) means the sum of nitric oxide and nitrogen dioxide in the flue gas or emission point, collectively expressed as nitrogen dioxide.

(j) Ozone season means for each state (or portion of a state), the ozone monitoring season as defined in 40 CFR part 58, appendix D, section 4.1(i) for that state (or portion of a state).

(k) Ozone transport region (OTR) means the area established by CAA section 184(a) or any other area established by the Administrator pursuant to CAA section 176A for purposes of ozone.

(l) Reasonable further progress (RFP) means the emissions reductions required under CAA sections 172(c)(2), 182(c)(2)(B), 182(c)(2)(C), and § 51.1310. The EPA interprets RFP under CAA section 172(c)(2) to be an average 3 percent per year emissions reduction of either VOC or NO_X.

(m) Rate-of-progress (ROP) means the 15 percent progress reductions in VOC emissions over the first 6 years after the baseline year required under CAA section 182(b)(1).

(n) I/M refers to the inspection and maintenance programs for in-use vehicles required under the 1990 CAA Amendments and defined by subpart S of 40 CFR part 51.

(o) Current ozone NAAQS means the most recently promulgated ozone NAAQS at the time of application of any provision of this subpart.

(p) Base year inventory for the nonattainment area means a comprehensive, accurate, current inventory of actual emissions from sources of VOC and NO_X emitted within the boundaries of the nonattainment area as required by CAA section 182(a)(1).

(q) Ozone season day emissions means an average day's emissions for a typical ozone season work weekday. The state shall select, subject to EPA approval, the particular month(s) in the ozone season and the day(s) in the work week to be represented, considering the conditions assumed in the development of RFP plans and/or emissions budgets for transportation conformity.