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Regulations for Emissions from Vehicles and Engines

Improvements for Heavy-Duty Engine and Vehicle Test Procedures - Supplemental Notice of Proposed Rulemaking

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Rule Summary

EPA is publishing a supplemental notice of proposed rulemaking (SNPRM) to improve the Greenhouse gas Emissions Model (GEM) compliance tool for heavy-duty vehicles while more closely matching the outputs produced by the original GEM version 3.0 that was used to establish the CO2 standards for Model Years 2021 and later in the 2016 Heavy-duty Phase 2 final rule.

These amendments would:

  • Improve the GEM compliance tool
  • Increase compliance flexibility
  • Include adjustment factors for GEM outputs
  • Clarify existing requirements
  • Correct errors

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