According to the EPA, about 10,000 semi-truck glider kits are sold in the U.S. each year. Glider kits consist of new truck bodies fitted with remanufactured or salvaged engines and transmissions that do not use exhaust gas recirculation and do not require exhaust gas after-treatment. Because of this, an EPA study in 2017 found that NOx emissions were as much as 43 times higher on glider kit vehicles than on compliant trucks. Particulate matter emissions were up to 450 times higher.

Under the Obama administration, glider kits were to be limited to 300 per year in 2018. In July 2018, the EPA announced it was exercising its enforcement discretion in 2018 and would not enforce the 300 per-year kit cap. An environmental coalition and 16 state attorney generals filed requests for review by the U.S. Court of Appeals for the District of Columbia claiming that not enforcing the glider provisions in the 2016 Phase 2 heavy truck greenhouse gas rule would allow thousands of glider trucks on U.S. roadways. The court quickly issued a temporary stay of the EPA Nonenforcement Plan. Then, on July 26, acting EPA Administrator, Andrew Wheeler, reversed the controversial decision so the polluting trucks are once again an endangered species.