On November 13, 2018, EPA announced the Cleaner TrucksInitiative (CTI), a future rulemaking to update standards for nitrogen oxide (NOx) emissions from highway heavy-duty trucks and engines. More information on the CTI can be found at:
https://www.epa.gov/newsreleases/epa-acting-administrator-wheeler-launches-cleaner-trucks-initiative
https://www.epa.gov/regulations-emissions-vehicles-and-engines/cleaner-truck-initiative
Petitions for Revised NOx Standards for On-highway Heavy-duty Engines and Trucks: