SUPPLEMENTARY INFORMATION:

Throughout this document whenever “we,” “us,” or “our” is used, we mean the EPA.

Table of Contents

I. Introduction

II. Proposed Action

III. Background and Purpose

A. Carbon Monoxide and Ozone NAAQS Attainment History

B. History of Vehicle I/M Program in New Hampshire

IV. EPA Evaluation of Section 110(l) Analysis

V. Statutory and Executive Order Reviews

I. Introduction

On December 24, 2025, the State of New Hampshire petitioned the EPA pursuant to CAA section 176A(a)(2) for the removal of the State of New Hampshire from the Ozone Transport Region (OTR). Section 184(b) of the CAA establishes specific control requirements that each State in the OTR is required to implement within the State, including certain controls on sources of nitrogen oxides (NO_X) and volatile organic compounds (VOCs). These control requirements are required to be implemented in any State included within the OTR, regardless of ozone attainment status. Under CAA section 184(b)(1)(A), OTR States must include vehicle I/M programs in their SIPs.

Section 176A(a)(2) of the CAA states that the Administrator may remove any state or portion of a state from the OTR whenever the Administrator has reason to believe that the control of emissions in that state or portion of that state pursuant to its inclusion in the transport region will not significantly contribute to the attainment of the standard in any area in the region. In its 176A petition to be removed from the OTR, New Hampshire committed to retaining all existing OTR control measures in its SIP, except the vehicle I/M program. In a separate document, the EPA evaluates, and proposes to grant, New Hampshire's 176A petition. In the document you are reading now, the EPA addresses New Hampshire's SIP revision regarding the I/M program, which contains a section 110(l) analysis, as required by the CAA. NHDES consulted with the EPA during the development of the CAA section 110(l) demonstration, and the EPA finds that the methodology in this demonstration supports this proposed action.

For the reasons fully described in this document, and in consideration of the data submitted by NHDES, including impacts to air quality, the EPA proposes to find that removal of the I/M program as an active SIP measure will not interfere with attainment or maintenance of the NAAQS or any other applicable CAA requirements.

II. Proposed Action

The EPA is proposing to conditionally approve New Hampshire's SIP revision, submitted on December 24, 2025, to remove the State's I/M program as an active SIP measure and to include it on the list of potential contingency measures for the 1997 ozone NAAQS maintenance area in southern New Hampshire.^[2] The EPA is soliciting public comments on the EPA's proposal. Interested parties may participate in the Federal rulemaking procedure by submitting written comments to this proposed rule by following the ( printed page 51641) instructions listed in the ADDRESSES section of this Federal Register .

Under CAA section 110(k)(4), the EPA may conditionally approve a plan revision based on a commitment from the State to adopt specific enforceable measures by a date certain, but not later than one year from the date of approval. If the EPA conditionally approves the December 24, 2025, SIP revision in a final rulemaking action, the State must meet its commitment to submit a SIP revision addressing the requirement of CAA section 175A(d). If the State fails to do so, this action will become a disapproval one year from the date of final approval. The EPA will notify the State by letter that this action has occurred. The EPA subsequently will publish a document in the Federal Register notifying the public that the conditional approval automatically converted to a disapproval. If the State meets its commitment within the applicable time frame, the I/M program will remain on the list of potential contingency measures for the maintenance area unless the EPA takes final action disapproving the new submittal. If the EPA disapproves the new submittal, the request to remove the I/M program as an active control measure and include it on the list of potential contingency measures will be disapproved at that time. If the EPA approves the submittal, the December 24, 2025, revision will be fully approved in its entirety, and the I/M program will remain on the list of potential contingency measures for the maintenance area.

III. Background and Purpose

New Hampshire has enacted legislation, House Bill 2 (HB2), mandating the repeal of the motor vehicle I/M program under portions of New Hampshire's Revised Statute Annotated (RSA) Chapter 266 Equipment of Vehicles, Chapter 260 Administration of Motor Vehicle Laws, and Chapter 125-S Motor Vehicle Abatement Fund, effective January 31, 2026.^[3] Consequently, the NHDES submitted a SIP revision on December 24, 2025, to remove the I/M program from the SIP, including those sections of the New Hampshire Code of Administrative Rules Chapter Saf-C 3200 Official Motor Vehicle Inspection Requirements regulation, most recently approved into the New Hampshire SIP in a final rulemaking published April 29, 2024.^[4] On June 11, 2026, NHDES supplemented the current SIP submittal with a letter to the EPA committing to submit an additional SIP revision requesting that the I/M program be included on the list of potential contingency measures portion of the maintenance plan pertaining to the 1997 ozone NAAQS.^[5]

A. Carbon Monoxide and Ozone NAAQS Attainment History

Two areas in New Hampshire, the City of Manchester and the City of Nashua, were designated nonattainment for the 1971 8-hour and 1-hour CO NAAQS, which are 9 ppm and 35 ppm, respectively, both not to be exceeded more than once per year. The CAA required these areas to achieve the CO NAAQS by November 15, 1995.^[6] The EPA redesignated the City of Nashua and the City of Manchester from nonattainment to attainment for CO and approved the first maintenance plans for both, effective January 29, 2001.^[7] The 1999 CO NAAQS redesignation requests from New Hampshire contained CO motor vehicle emissions budgets (budgets) of 55.83 tons per winter day for Manchester, and 60.13 tons per winter day for Nashua. These budgets were considered adequate for transportation conformity purposes. For the second 10-year period, 2011-2021, NHDES submitted a limited maintenance plan (LMP) to the EPA, committing to continuing to implement the I/M program and other emissions reduction strategies during the 10-year period of the LMP. In the LMP, New Hampshire projected CO emissions in 2026 of 26.38 tons per winter day for the City of Manchester and 25.51 tons per winter day for the City of Nashua, both of which are significantly below the initial tons per winter day budgets set for each location in the redesignation requests. The EPA approved the LMP, effective April 9, 2014. The 20-year maintenance period for the CO NAAQS ended in 2021.^[8]

Consistent with the 1990 CAA Amendments, which established a classification system for nonattainment areas, several New Hampshire counties were designated as nonattainment of the now-revoked 1979 1-hour ozone NAAQS (0.12 parts per million (ppm)).^[9] In 2012, the EPA determined that these areas met the revoked 1-hour ozone standard by the areas' respective, applicable attainment dates.^[10] On July 18, 1997, the EPA revised the ozone primary and secondary NAAQS to 0.08 ppm and the averaging time from 1-hour to 8-hour (annual fourth-highest daily maximum 8-hour concentration, averaged over three years).^[11] The EPA initially designated the three New Hampshire nonattainment areas (two Serious and one Marginal) as a single area, the New Hampshire portion of the Boston-Manchester-Portsmouth area under the 1997 8-hour ozone NAAQS. New Hampshire submitted a redesignation request, maintenance plan, requisite emission inventory and budgets for the Boston-Manchester-Portsmouth area related to the 1997 8-hour ozone NAAQS on March 2, 2012, supplemented on September 21, 2012. The EPA redesignated the Boston-Manchester-Portsmouth area to attainment of the 1997 8-hour ozone NAAQS on January 31, 2013.^[12] Although the EPA revoked the 1997 8-hour ozone NAAQS in 2015, certain CAA requirements remain in place, such as a second maintenance plan.^[13] Accordingly, NHDES submitted an LMP to the EPA for the second 10-year maintenance period (2023-2032) for the Boston-Manchester-Portsmouth area on July 29, 2021, which the EPA approved on April 22, 2022.^[14] Finally, the entire State of New Hampshire is also designated attainment/unclassifiable for the 2008 and 2015 ozone NAAQS.^[15]

B. History of Vehicle I/M Program in New Hampshire

The CAA requires I/M programs for ozone and CO nonattainment areas based upon certain criteria, such as air quality status and population.^[16] Additionally, certain areas in the OTR ( printed page 51642) are required to implement I/M programs pursuant to CAA section 184(b)(1)(A). Currently, all of New Hampshire, as well as all or portions of eleven other States and the District of Columbia comprise the OTR. As stated in the previous section, portions of New Hampshire used to be in nonattainment under the CO, 1979 1-hour ozone, and 1997 8-hour ozone NAAQS but have since redesignated to attainment, and the entire State is designated attainment for the 2008 and 2015 ozone NAAQS.^[17] Thus, there are no outstanding I/M implementation requirements due to nonattainment designations, and New Hampshire's obligation to implement a vehicle I/M program is now due only to its inclusion in the OTR. Concurrently with this proposed SIP revision, the EPA has in a separate action proposed to grant New Hampshire's petition to remove the State from the OTR pursuant to CAA section 176A(a)(2).^[18]

The EPA's I/M rule was established on November 5, 1992.^[19] The EPA made significant revisions to the I/M rule on September 18, 1995, and on July 25, 1996.^[20 21] The I/M regulations are codified at 40 CFR part 51, subpart S, and generally require a State in the OTR to have an Enhanced I/M program in its SIP that covers areas of the State within a metropolitan statistical area (MSA), but a State may choose to include additional areas outside of any MSA, as well. New Hampshire chose to include the entire State in its Enhanced I/M program.

States subject to the I/M requirement are to submit an I/M SIP revision that addresses the elements necessary to implement I/M as specified in the EPA's I/M rule at 40 CFR part 51, subpart S. The most recent revision to New Hampshire's I/M SIP was submitted on September 22, 2022, and included amendments to the Department of Safety Chapter Saf-C 3200, Official Motor Vehicle Inspection Requirements. The remaining technical aspects of the I/M SIP, including emission modeling and other technical documentation included in prior I/M SIP revisions, were still applicable to the technical demonstration that New Hampshire's Enhanced I/M program met the requirements of 40 CFR part 51, subpart S. Therefore, the EPA approved this revision into the New Hampshire SIP, effective May 29, 2024.^[22] For a further detailed history of the State's I/M program, see section 2.5.2 of New Hampshire's December 24, 2025, submittal.

In sum, New Hampshire is attaining the CO and ozone standards, which are the criteria pollutants I/M programs are designed to address. While the State is well within the attainment limits for all other criteria pollutants, there are no emissions reductions from the I/M program attributable to the direct emissions of particulate matter, lead, and sulfur dioxide (SO₂). Additionally, nitrogen dioxide (NO₂) is captured generally through consideration of NO_X impacts, and the PM_2.5 precursor pollutants, NO_X and VOCs, are already addressed by the consideration of ozone precursors, which are also NO_X and VOCs. In addition, while CAA section 184(b)(1)(A) requires New Hampshire's SIP to provide for an I/M program because the State is in the OTR, the EPA is concurrently proposing in a separate action to grant New Hampshire's request pursuant to CAA section 176A(a)(2) to be removed from the OTR. The EPA will not finalize the proposal to remove the I/M program as an active control measure and include it on New Hampshire's list of contingency provisions for the maintenance area unless and until the EPA grants New Hampshire's request to be removed from the OTR.

IV. EPA Evaluation of Section 110(l) Analysis

The December 24, 2025 New Hampshire SIP revision seeking the removal of the I/M program from the SIP includes an evaluation of monitored design values and emissions data. The data show a consistent downward trend in CO design values since the initial designation, with negligible design values since 2014 ( i.e., <1 ppm). New Hampshire has also shown an overall downward trend in ozone design values since the 1980s, with the three most recent design value periods consistently below the current, and most stringent, 8-hour ozone NAAQS of 70 parts per billion (ppb) in the State.^[23] Notably, the current 2022-2024 design values across all 12 monitoring sites measure a statewide maximum of 65 ppb or below.

For the non-interference demonstration pursuant to CAA section 110(l), NHDES used the National Emissions Collaborative's 2022v1 Emissions Modeling Platform (EMP), using 2022 as the base year and 2026 as the future analytic year. The analysis focuses on CO and ozone precursor pollutants, NO_X and VOC. The 2022 base year serves as a baseline for comparison of future projected emissions and includes emissions benefits from the I/M program. NHDES considered two options for a base year emissions inventory, the 2020 NEI and the 2022v1 EMP. Ultimately, NHDES decided on 2022, since using 2020 data may not realistically represent vehicle emissions due to VMT decreases in that year resulting from the COVID-19 pandemic. NHDES chose 2026 for future-year analysis since it is the same year the I/M discontinuation is slated to take effect and thus coincides with the removal of emissions benefits from the New Hampshire I/M program. NHDES consulted with the EPA during the development of this demonstration, and the EPA finds that the methodology in the CAA section 110(l) demonstration supports this proposed action.

NHDES used the latest version of the EPA's mobile source emissions model, Motor Vehicle Emission Simulator (MOVES5), to quantify 2026 projected emissions from on-road vehicles without the I/M program and replaced the EMP on-road mobile emissions estimates. Additionally, NHDES estimated its own 2022 on-road mobile emissions using MOVES5 to ensure an accurate comparison, since the EMP used the previous MOVES4 model to calculate 2022 on-road mobile emissions. For more detailed information on the methodologies, assumptions, and data inputs used, see attachment 3 of the NHDES December 24, 2025, SIP submittal.

Even with the discontinuation of the I/M program, the State's submittal shows a reduction in NOx, VOC, and CO emissions by 16.0%, 2.7% and 1.9%, respectively, from the 2022 base year with I/M to the 2026 projected year without I/M. This continued decrease in emissions, despite projected increases in VMT, is generally agreed to be partially a result of fleet turnover, with old vehicles being replaced with newer, lower emitting vehicles that meet more stringent engine and emission standards.^{[24 25 26]} Additionally, since all ( printed page 51643) areas in New Hampshire are designated attainment for all applicable NAAQS with current emissions levels, we are proposing to approve the State's conclusion that New Hampshire will continue to attain in the future with projected emissions reductions. The EPA agrees with New Hampshire's conclusion that on-road mobile source emissions are expected to decline even without implementation of the State's I/M program. New Hampshire is also retaining all other active control measures in the SIP that were implemented due to New Hampshire's inclusion in the OTR, ensuring New Hampshire remains in attainment. Additionally, in previous rulemakings, the EPA determined that New Hampshire does not significantly contribute to nonattainment, or interfere with maintenance, of the 2008 and 2015 ozone NAAQS.^[27] New Hampshire's removal of its I/M program does not affect the prior non-contribution findings, because the reductions attributed to New Hampshire's I/M program are minor and have been overtaken by greater emissions reductions from other mitigation measures, like fleet turnover, since those previous rulemakings.

Since the maintenance plan for the New Hampshire portion of the Boston-Manchester-Portsmouth area for the revoked 1997 8-hour ozone NAAQS is still active, New Hampshire may remove the I/M program as an active control measure but must include it in its list of potential contingency measures for the maintenance area in accordance with CAA section 175A(d). To address this requirement, New Hampshire has committed to submit a SIP revision which will formally request the EPA approval to include the I/M program on the list of potential contingency measures portion of the 1997 8-hour ozone NAAQS maintenance plan. The forthcoming SIP revision must be submitted no later than one year from a final conditional approval of the December 24, 2025, I/M SIP revision.

Because 2026 emissions without the I/M program are projected to be lower than the 2022 emissions with the I/M program, the EPA proposes to find that the State's submittal demonstrates that the removal of the I/M program in New Hampshire will not interfere with attainment or maintenance of the NAAQS or any other applicable CAA requirements.^[28] Further, because New Hampshire has committed to submit a SIP revision to include the I/M program on the list of potential contingency measures, the EPA proposes to conditionally approve the current SIP revision.

V. Statutory and Executive Order Reviews

Under the CAA, the Administrator is required to approve a SIP submission that complies with the provisions of the CAA and applicable Federal regulations. See42 U.S.C. 7410(k); 40 CFR 52.02(a). Thus, in reviewing SIP submissions, the EPA's role is to approve State choices, provided that they meet the criteria of the CAA. Accordingly, this proposed action merely approves State law as meeting Federal requirements and does not impose additional requirements beyond those imposed by State law. For that reason, this proposed action:

• Is not a significant regulatory action subject to review by the Office of Management and Budget under Executive Orders12866 (58 FR 51735, October 4, 1993);
• Is not subject to anExecutive Order 14192 (90 FR 9065, February 6, 2025) regulatory action because this action is not significant under Executive Order 12866;
• Does not impose an information collection burden under the provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
• Is certified as not having a significant economic impact on a substantial number of small entities under the Regulatory Flexibility Act (5 U.S.C. 601 et seq.);
• Does not contain any unfunded mandate or significantly or uniquely affect small governments, as described in the Unfunded Mandates Reform Act of 1995 (Pub. L. 104-4);
• Does not have federalism implications as specified inExecutive Order 13132 (64 FR 43255, August 10, 1999);
• Is not subject toExecutive Order 13045 (62 FR 19885, April 23, 1997) because it approves a state program;
• Is not a significant regulatory action subject toExecutive Order 13211 (66 FR 28355, May 22, 2001); and
• Is not subject to requirements of section 12(d) of the National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272 note) because application of those requirements would be inconsistent with the CAA.

In addition, the SIP is not approved to apply on any Indian reservation land or in any other area where the EPA or an Indian Tribe has demonstrated that a Tribe has jurisdiction. In those areas of Indian country, the rule does not have Tribal implications and will not impose substantial direct costs on Tribal governments or preempt Tribal law as specified by Executive Order 13175 (65 FR 67249, November 9, 2000).

( printed page 51644) Authority: 42 U.S.C. 7401 et seq.

91 FR 51640