Where do U.S. transportation emissions come from?Emissions from transportation activities mainly come from the combustion of gasoline, diesel, jet fuel, and other petroleum liquids. The majority of U.S. transportation emissions are produced by on-road vehicles ‐ in particular light-duty trucks. LDTs, which include SUVs, pickup trucks, and minivans, accounted for more than one-third of the sector’s GHG emissions in 2021. Medium and heavy-duty trucks and passenger cars followed, each with shares above 20 percent. Passenger car emissions had previously been far higher, but they have been cut by more than 40 percent since 1990 due to improved efficiency, increasingly stringent emissions standards, and more recently, an uptake in alternative fuel vehicles.
On a state-by-state basis, the biggest contributor to U.S. transportation emissions is Texas. Despite a COVID-19 induced year-on-year reduction of 15 percent, Texas emitted 193 MtCO₂ in 2020. This was almost 20 percent more than in second-placed California and at least twice those of every other state.