The letter comes one week after the EPA announced that it would not enforce a 2016 regulation that limits the manufacture of diesel freight trucks refurbished with older engines.
A protester watches a burning traffic circle while union trade members block trucks on September 25th, 2017, in Donges, France, to protest the government's labor law.
Long-haul truck driving is thriving in the United States, and remains one of the surest ways into the middle class, but minorities say discrimination is rampant.