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Testing and Measuring Emissions

Vehicle Testing Regulations

EPA has adopted emission standards for motor vehicles and certain kinds of nonroad vehicles and equipment.  To show compliance with these emission standards, manufacturers must follow test procedures specified in the Code of Federal Regulations. This page provides links to the appropriate regulatory citations and includes published information related to the test procedures. These links include a general set of instructions and requirements for manufacturers to measure emissions for certifying their vehicles to EPA emission standards.

The test procedures referenced on this page are related to chassis-based exhaust emission standards, and may also include evaporative emission measurement procedures.  See Engine Testing Regulations for information on test procedures for measuring exhaust emissions using engine-based test procedures.

The following table shows which test procedures apply for each category:

Vehicle Category

Code of Federal Register Citation

Light-duty vehicles, light-duty trucks, and heavy-duty vehicles at or below 14,000 pounds GVWR subject to standards under 40 CFR part 86, subpart S

40 CFR part 86, subpart B (through 2021 model year)
40 CFR part 1066 (optional through 2021 model year; mandatory starting in 2022 model year)

Heavy-duty vehicles above 14,000 pounds GVWR, and heavy-duty vehicles at or below 14,000 pounds GVWR not subject to standards under 40 CFR part 86, subpart S

40 CFR part 1066

Highway motorcycles

40 CFR part 86, subpart F

Off-highway motorcycles and all-terrain vehicles

40 CFR part 86, subpart F


You will need Adobe Acrobat Reader to view the Adobe PDF files on this page. See EPA's PDF page for more information about getting and using the free Acrobat Reader.

The original regulations for part 1066 were adopted in 2011.  EPA has amended these regulations in subsequent rulemakings, both to expand the scope of vehicles covered by part 1066 and to improve the procedures.  The current part 1066 procedures are available in the electronic Code of Federal Regulations.  Note that when we make changes to the part 1066 test procedures, manufacturers that are already subject to testing under part 1066 may take up to 12 months to comply with the new specifications.  The following list of final rules includes all the changes we have made to part 1066.  For the most recent rules, the description includes the specific dates on which compliance with the regulatory changes become mandatory.

  • February 19, 2015 Direct Final Rule (PDF) (48 pp, 1.04MB)
    This rule included minor amendments to part 1065, mostly to correct and clarify provisions associated with the Tier 3 standards for motor vehicles. See “2015 Amendments” for additional rulemaking documents. These amendments became legally effective on May 5, 2015, though they do not become mandatory until May 5, 2016 under §1065.10(c)(6).
  • April 28, 2014 Final Rule (PDF) (474 pp, 6.6MB)

    This rule included new standards for motor vehicles subject to vehicle-based emission standards and test procedures, and included a wide range of amendments to part 1065. See Tier 3 Final Rule for additional rulemaking documents.  These amendments become legally effective June 27, 2014, though they do not become mandatory until June 27, 2015 under §1066.10(c) and §1065.10(c)(6).

  • June 17, 2013 Direct Final Rule (PDF) (38 pp, 652KB)

    This rule included a range of amendments related to heavy-duty greenhouse gas emission standards, including several changes to the test procedures in part 1066.  See Heavy-Duty Greenhouse Gas Amendments for additional rulemaking documents. 

  • September 15, 2011 Final Rule (PDF) (408 pp, 4.78MB)

    This was the initial publication of part 1066.  See Heavy-Duty Greenhouse Gas Final Rule for additional rulemaking documents.

For further information or assistance regarding this web page, please contact Alan Stout, phone: (734) 214-4805 or email: stout.alan@epa.gov.

This page is maintained by EPA's Office of Transportation and Air Quality (OTAQ).
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