(a) Transportation plans adopted after January 1, 1997 in serious, severe, or extreme ozone nonattainment areas and in serious CO nonattainment areas. If the metropolitan planning area contains an urbanized area population greater than 200,000, the transportation plan must specifically describe the transportation system envisioned for certain future years which shall be called horizon years.

(1) The agency or organization developing the transportation plan may choose any years to be horizon years, subject to the following restrictions:

(i) Horizon years may be no more than 10 years apart;

(ii) The first horizon year may be no more than 10 years from the base year used to validate the transportation demand planning model;

(iii) The attainment year must be a horizon year if it is in the timeframe of the transportation plan and conformity determination;

(iv) The last year of the transportation plan's forecast period must be a horizon year; and

(v) If the timeframe of the conformity determination has been shortened under paragraph (d) of this section, the last year of the timeframe of the conformity determination must be a horizon year.

(2) For these horizon years:

(i) The transportation plan shall quantify and document the demographic and employment factors influencing expected transportation demand, including land use forecasts, in accordance with implementation plan provisions and the consultation requirements specified by § 93.105;

(ii) The highway and transit system shall be described in terms of the regionally significant additions or modifications to the existing transportation network which the transportation plan envisions to be operational in the horizon years. Additions and modifications to the highway network shall be sufficiently identified to indicate intersections with existing regionally significant facilities, and to determine their effect on route options between transportation analysis zones. Each added or modified highway segment shall also be sufficiently identified in terms of its design concept and design scope to allow modeling of travel times under various traffic volumes, consistent with the modeling methods for area-wide transportation analysis in use by the MPO. Transit facilities, equipment, and services envisioned for the future shall be identified in terms of design concept, design scope, and operating policies that are sufficient for modeling of their transit ridership. Additions and modifications to the transportation network shall be described sufficiently to show that there is a reasonable relationship between expected land use and the envisioned transportation system; and

(iii) Other future transportation policies, requirements, services, and activities, including intermodal activities, shall be described.

(b) Two-year grace period for transportation plan requirements in certain ozone and CO areas. The requirements of paragraph (a) of this section apply to such areas or portions of such areas that have previously not been required to meet these requirements for any existing NAAQS two years from the following:

(1) The effective date of EPA's reclassification of an ozone or CO nonattainment area that has an urbanized area population greater than 200,000 to serious or above;

(2) The official notice by the Census Bureau that determines the urbanized area population of a serious or above ozone or CO nonattainment area to be greater than 200,000; or,

(3) The effective date of EPA's action that classifies a newly designated ozone or CO nonattainment area that has an urbanized area population greater than 200,000 as serious or above.

(c) Transportation plans for other areas. Transportation plans for other areas must meet the requirements of paragraph (a) of this section at least to the extent it has been the previous practice of the MPO to prepare plans which meet those requirements. Otherwise, the transportation system envisioned for the future must be sufficiently described within the transportation plans so that a conformity determination can be made according to the criteria and procedures of §§ 93.109 through 93.119.

(d) Timeframe of conformity determination. (1) Unless an election is made under paragraph (d)(2) or (d)(3) of this section, the timeframe of the conformity determination must be through the last year of the transportation plan's forecast period.

(2) For areas that do not have an adequate or approved CAA section 175A(b) maintenance plan, the MPO may elect to shorten the timeframe of the transportation plan and TIP conformity determination, after consultation with state and local air quality agencies, solicitation of public comments, and consideration of such comments.

(i) The shortened timeframe of the conformity determination must extend at least to the latest of the following years:

(A) The tenth year of the transportation plan;

(B) The latest year for which an adequate or approved motor vehicle emissions budget(s) is established in the submitted or applicable implementation plan; or

(C) The year after the completion date of a regionally significant project if the project is included in the TIP or the project requires approval before the subsequent conformity determination.

(ii) The conformity determination must be accompanied by a regional emissions analysis (for informational purposes only) for the last year of the transportation plan and for any year shown to exceed motor vehicle emissions budgets in a prior regional emissions analysis, if such a year extends beyond the timeframe of the conformity determination.

(3) For areas that have an adequate or approved CAA section 175A(b) maintenance plan, the MPO may elect to shorten the timeframe of the conformity determination to extend through the last year of such maintenance plan after consultation with state and local air quality agencies, solicitation of public comments, and consideration of such comments.

(4) Any election made by an MPO under paragraphs (d)(2) or (d)(3) of this section shall continue in effect until the MPO elects otherwise, after consultation with state and local air quality agencies, solicitation of public comments, and consideration of such comments.

(e) Savings. The requirements of this section supplement other requirements of applicable law or regulation governing the format or content of transportation plans.