Clean Air Act Amendments create EPA emission standards, grouped by tiers and bins, for all new vehicles sold in the U.S.
Tier 2. In 2000 the EPA set Tier 2 standards, phased in over a decade, for gasoline vehicle emissions and their fuel (making oil refiners produce cleaner gasoline with less sulfur). Sulfur reduction in gasoline is key because sulfur damages the catalysts and filters that are most effective at reducing tailpipe emissions.
Tier 3. Amendments to the Clear Air Act will continue to make the standards more strict for new vehicles. The EPA is working toward further reductions with Tier 3. By harmonizing Tier 3 with California’s stricter standards, manufacturers would be able to make the same version of a vehicle for all fifty states.
EPA Bin Numbers and CARB Classifications. Federal EPA bin numbers and CARB classifications identify the level of a vehicle’s emissions.