Two federal agencies share the heavy-duty Phase 2 rule published October 25, 2016, but they do not regulate exactly the same thing. EPA sets carbon-dioxide emissions standards while NHTSA sets fuel-consumption standards. Their final program, effective December 27, covers new medium- and heavy-duty vehicles through several categories rather than one universal truck target. [2016-21203][2015-15500]

The categories are combination tractors, trailers used with those tractors, heavy-duty pickups and vans, and vocational vehicles. Separate engine standards apply to engines powering tractors and vocational vehicles. Some requirements belong only to EPA, including controls on air-conditioning refrigerant leakage in vocational vehicles and methane and nitrous-oxide standards for heavy-duty engines. Coordination does not erase those differences in scope. [2016-21203][2015-15500]

The July 13, 2015 proposal helps explain this architecture: it already paired fuel-consumption and carbon-dioxide standards while distinguishing EPA-specific controls. That document was a proposal, not the final requirements. The two texts trace one EPA–NHTSA regulatory process, rather than offering independent corroboration that the projected benefits will occur. The final rule is the relevant source for what the agencies adopted. [2016-21203][2015-15500]

Timing requires a similar distinction. December 27 is the rule's effective date, not the date when every terminal standard applies. The final program phases through model year 2027, with interim steps in 2021 and 2024 and earlier EPA standards for certain trailers in 2018. Readers should identify the agency, vehicle category and model year before interpreting a requirement; expected savings remain forecasts rather than observed outcomes. [2016-21203][2015-15500]

Source documents

  1. Greenhouse Gas Emissions and Fuel Efficiency Standards for Medium- and Heavy-Duty Engines and Vehicles-Phase 2https://www.govinfo.gov/content/pkg/FR-2016-10-25/html/2016-21203.htm
  2. Heavy-duty vehicle Phase 2 proposalhttps://www.govinfo.gov/content/pkg/FR-2015-07-13/html/2015-15500.htm