An official website of the United States government.

This is not the current EPA website. To navigate to the current EPA website, please go to This website is historical material reflecting the EPA website as it existed on January 19, 2021. This website is no longer updated and links to external websites and some internal pages may not work. More information »

Vehicle and Fuel Emissions Testing

Vehicle Testing Regulations

On this page:


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 in order to certify 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.

IMPORTANT NOTE: When EPA makes changes to 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. 

Top of Page


Applicable Vehicle Test Procedures for Each Vehicle Category

The following table shows which vehicle test procedures apply for each vehicle category. For ease of use, Electronic Code of Federal Regulations (e-CFR) links are provided.

Vehicle Category Description Corresponding Regulation Page Corresponding e-CFR Link(s)
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 Regulations for emissions from passenger cars and vehicles (light-duty)
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 Regulations for emissions from commercial trucks and buses (heavy-duty)
Highway motorcycles Regulations for emissions from motorcycles
Off-highway motorcycles and all-terrain vehicles Regulations for emissions from recreational vehicles

Top of Page

List of Related Regulations

40 CFR part 1066 provides regulations for the required testing procedures for measuring exhaust, evaporative, and refueling emissions. These test procedures apply to both heavy-duty and light-duty vehicles. The following list of regulations shows all the changes made to part 1066.


For help on using the table:
Click the regulation titles for additional information, including:
  • Regulations;
  • Regulatory impact analyses;
  • Comment summaries;
  • Rule histories (including proposed rules); and/or
  • Fact sheets.

NOTE: Rule-related materials vary by rule.

Regulation Title Summary of Rule and Applicability to Testing Regulation Publish Date
Vehicle Test Procedure Adjustments for Tier 3 Certification Test Fuel EPA is proposing technical changes to emissions testing protocols and compliance calculations for the Light-duty Greenhouse Gas (GHG) Emissions Standards and Fuel Economy Standards that will to provide a smooth transition from using test fuel with zero percent ethanol (E0) to test fuel that contains ten percent ethanol (E10). 2020/4
Greenhouse Gas Emissions and Fuel Efficiency Standards for Medium- and Heavy-Duty Engines and Vehicles - Phase 2 This rule included substantial amendments to part 1066 to account for the new and revised test procedures for the greenhouse gas emission standards for heavy-duty vehicles, and to update procedures generally. 2016/10
Amendments Related to Tier 3 Motor Vehicle Emission and Fuel Standards, Nonroad Engine and Equipment Programs, and MARPOL Annex VI Implementation This rule included minor amendments to part 1065, mostly to correct and clarify provisions associated with the Tier 3 standards for motor vehicles. 2015/02
Final Rule for Control of Air Pollution from Motor Vehicles: Tier 3 Motor Vehicle Emission and Fuel Standards 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. 2014/04
Direct Final Rule for Heavy-Duty Engine and Vehicle, and Nonroad Technical Amendments Range of amendments to heavy-duty greenhouse gas emission standards, including several changes to test procedures in part 1066. 2013/07
Final Rule for Greenhouse Gas Emissions Standards and Fuel Efficiency Standards for Medium- and Heavy-Duty Engines and Vehicles Initial publication of part 1066. 2011/09

Top of Page