EPA Releases Final NOx Rule for Heavy-Duty Trucks

On December 20, 2022, the Environmental Protection Agency (EPA) has adopted its final NOx rule entitled, “Control of Air Pollution from New Motor Vehicles: Heavy-Duty Engine and Vehicle Standards.”
The EPA believes this final rule will set “stronger emissions standards to further reduce air pollution, from heavy-duty vehicles and engines starting in Model Year 2027.” Lastly, the EPA projects that by 2045, this final rule will reduce Nitrogen Oxide (NOx) emissions from the in-use fleet of heavy-duty trucks by almost 50%. 
The new EPA standards require heavy-duty commercial vehicles to limit NOx emissions to 0.035 grams per horsepower-hour during normal operation, 0.050 grams at low load, and 10.0 grams at idle.
The new emissions standards also impact vehicles by forcing more stringent standards for a longer period of time of when these engines operate on the road. It is estimated that the new NOx rules will increase the useful life of heavy-duty trucks by 1.5 to 2.5 times and will yield emissions warranties that are 2.8 to 4.5 times longer. These longer useful lifespans and warranty periods guarantee that as target vehicles age, they will continue to meet the EPA's more stringent emissions standards for a longer period.
In March 2022, the EPA released their Notice of Proposed Rulemaking (NPRM) for the Clean Trucks Plan. At the time, the EPA proposed two options for reducing NOx. Option 1 was the more stringent of the NOx standards and would be a 2-step process that would have reduced NOx by 90% from .2 to .02 in Model Year (MY) 2031, putting the EPA at the same level as the California Air Resources Board's (CARB) NOx standard. Option 2 would have required manufacturers to reduce their NOx by 75% from .2 to .05 in 2027, setting a standard that is different than CARB's and likely creating a patchwork of different NOx rules from state to state. 
TRALA formally submitted its comments to the EPA on their Clean Trucks Plan. In its comments, TRALA focused on the economic and technological implausibility of the 90% reduction in NOx proposed by Option 1. In addition, TRALA encouraged the EPA to amend Option 2, which called for a 75% reduction in NOx. Option 2 would not have prevented CARB from adopting a different standard but would have instead forced all states to comply which would have essentially enacted a national standard. Option 2 also would have required the EPA to force CARB, as well as several other states that typically follow California's lead, to amend their NOx rules to meet the 75% reduction in NOx proposed in Option 2. 
This final rule is the first of three major actions being taken under EPA's Clean Trucks Plan. By the end of March 2023, the EPA intends to release the proposals for the remaining two steps in the Clean Trucks Plan:
Proposed “Phase 3” GHG standards for heavy-duty vehicles beginning with MY 2027
Proposed multipollutant standards for light- and medium-duty vehicles beginning with MY 2027.
These additional rulemakings will also take into account recent congressional action, including resources for electrification from the Inflation Reduction Act (IRA) and the Bipartisan Infrastructure Law (BIL) that promote cleaner vehicles.
The EPA will likely prioritize releasing decisions on the three pending heavy-duty program waiver requests from the state of California in early 2023. TRALA will continue to work with its allies to address the EPA's drastic emission reduction rules for trucks. 
You may view the final rule in its entirety by clicking here.
If you have any questions regarding this final EPA rule, please contact me at or Elizabeth Hyers at