The speed limiter law is one that has been in the works for a few years now, with proposals circulating at least since 2014. It also had broad support from both trucking companies such as the American Trucking Association and Road Safe America, as well as traditional safety agencies such as the Insurance Institute for Highway Safety. The National Highway Traffic Safety Administration's (NHTSA) most recent proposal suggested limiting trucks to 60, 65, or 68 mph, and the organization said that aside from safety, the regulation could save over $1 billion a year in fuel.
According to Bloomberg, this isn't the only safety regulation stopped up by the President's executive order, such as this sound regulation that would require relatively quiet hybrids and EVs to make noise below 19 mph and in reverse to prevent accidents. NHTSA estimated that 2,400 injuries could be prevented by implementing this mandate.