In 2020 the U.S. South-Central Region (Texas, New Mexico, Oklahoma, Arkansas, and Louisiana) had the highest share (54.5%) of registered heavy-duty diesel trucks equipped with selective catalytic reduction (SCR) and particulate matter (PM) control technologies. SCR reduces emissions of nitrogen oxides (NOx). EPA regulations have required all heavy-duty diesel trucks since model year 2010 to have these emission reduction technologies. Three regions—South-Central, Great Lakes (53.6%), and Mid-Atlantic (52.3%) surpassed the national average of 49%.
Source: Diesel Technology Forum, “43.3 Percent of Commercial Trucks Operating in EPA Regions 9 & 10 Now Powered by Newest-Generation Near-Zero Emissions Diesel Technology,” July 22, 2021. Original data from IHS/Markit.