Vehicle Emissions Inspection and Maintenance (I/M): Policy and Technical Guidance

• I/M Program Implementation
• I/M Program Annual Reporting, Modeling, and Program Evaluation

Vehicle inspection and maintenance (I/M) programs help improve air quality by identifying cars and trucks with high emissions and that may need repairs. Owners or operators of vehicles with high emissions are notified to make any repairs so that emissions are within legal limits. The 1990 Amendments to the Clean Air Act (CAA) established I/M requirements for several areas across the country. This page contains policy and technical guidance that EPA has developed on several topics.

I/M Program Implementation

• Guidance for On-Road Testing Requirements for Enhanced Vehicle Inspection and Maintenance (I/M) Programs (pdf) (169 KB, March 2020, EPA-420-B-20-020)
  This document provides guidance to clarify how the on-road testing requirement can be met in states with enhanced I/M programs.
• Vehicle Emission Inspection and Maintenance (I/M) Provision in the Fixing America’s Surface Transportation (FAST) Act (December 2016) This document provides clarification regarding the obligations of states versus EPA with regard to the I/M provision of the FAST Act exempting certain replica vehicles from I/M. Please note that the Clean Air Act amendment that was made as part of the FAST Act continues to apply as described in this guidance.
• Performing On-Board Diagnostic System Checks as Part of a Vehicle Inspection and Maintenance Program (pdf) (317 KB, June 2001, EPA420-R-01-015)
  The guidance document contains EPA's recommendations regarding the effective implementation of OBD-I/M checks in I/M programs. The recommendations contained in this guidance are consistent with EPA's amended OBD-I/M requirements, published April 5, 2001 (66 FR 18156).
  • This memo and accompanying documents below update Appendix D of the June 2001 guidance (above) with the list of vehicles that exhibit OBD monitor-related readiness issues and make suggestions for how I/M programs can improve operational performance by addressing monitor readiness.
  • Improving I/M Performance and OBD Monitor Readiness Memo (pdf) (30.44 KB, May 2011)
  • I/M OBD Vehicles Readiness Exception List (pdf) (194 KB, January 2008, EPA420-F-08-009)
  • OBD Readiness Testability Issues (pdf) (184 KB, June 2012, EPA-420-B-12-044)

I/M Program Annual Reporting, Modeling, and Program Evaluation

• Performance Standard Modeling for New and Existing Vehicle Inspection and Maintenance (I/M) Programs Using the MOVES Mobile Source Emissions Model (pdf) (895 KB, October 2022, EPA-420-B-22-034)

  This document describes the procedure for conducting performance standard modeling (PSM) to demonstrate that an I/M program meets the applicable performance standard, as defined within the I/M regulations (40 CFR Part 51, subpart S) and the Clean Air Act. This guidance supersedes the January 2014 version of this guidance (EPA-420-B-14-006). This guidance generally applies to future versions of MOVES. The templates have been updated for MOVES5 and are found below.

  October 2025 Update: EPA identified two places in the 2022 guidance that need numerical clarifications as described below. These clarifications will help practitioners follow the descriptive examples provided in the guidance, but they do not alter the substance of the document. These clarifications are as follows:

  • On page 23 (Section 2.20), the sentence should read:
    For example, some programs include a 20-year rolling exemption meaning that the newest 20 model years are tested.
  • On page 29 (Table 5), the NOx values for the Proposed/Existing I/M program and Performance Standard Benchmark program should be switched. This table demonstrates that NOx and VOC emissions from a proposed program should be lower than a benchmark program's emissions in order to meet the performance standard.

  Note: The Latest Version of MOVES should be used for new regulatory analyses involving an I/M program (such as performance standard modeling). For more information regarding the use of the latest version of MOVES for PSM, see Section 2.6 of the MOVES5 Policy Guidance (pdf) (386 KB, November 2024, EPA-420-B-24-038).

  • Basic 8-hour Ozone Performance Standard Benchmark MOVES5 Template (xlsx) (635.59 KB, March 2025)
    This is the Basic Performance Standard template to be used in MOVES5 as the “I/M Programs” input that reflects the I/M program design elements as specified in 40 CFR 51.352(e). This is to be used in PSM for areas needing to meet the Basic performance standard. For more information, please see Section 3 of the guidance document linked above.
  • Enhanced 8-hour Ozone Performance Standard Benchmark MOVES5 Template (xlsx) (637.23 KB, March 2025)
    This is the Enhanced Performance Standard template to be used in MOVES5 as the “I/M Programs” input that reflects the I/M program design elements as specified in 40 CFR 51.351(i). This is to be used in PSM for areas needing to meet the Enhanced performance standard. For more information, please see Section 3 of the guidance document linked above.
• Guidance on Vehicle Inspection and Maintenance (I/M) Test Data Statistics as Part of Annual I/M Reporting Requirements (pdf) (270 KB, May 2020, EPA-420-B-20-033)
  This document provides guidance to help states and local agencies develop required annual reports for I/M programs.
• Guidance on Biennial Performance Evaluation Requirements for Enhanced Vehicle Inspection and Maintenance (I/M) Programs (pdf) (724 KB, December 2022, EPA-420-B-22-042)
  This document provides guidance to clarify how the biennial performance evaluation requirements can be met for states with enhanced I/M programs. This document makes a minor update to the formula in Section 5 and the Appendix to be consistent with the MOVES3 Technical Guidance and supersedes the June 2020 version of this guidance (EPA-420-B-20-040).
• Guidance on the Use of Remote Sensing for Evaluation of I/M Program Performance (pdf) (639 KB, July 2004, EPA-420-B-04-010)
  This document is intended to provide states with technical guidance on how to perform biennial I/M program evaluations using RSD technology. See EPA's December 2022 Biennial Program Evaluation Guidance for further information about meeting this I/M requirement.