The announcement comes as California regulators are pushing for a new ultralow standard for nitrogen-oxide emissions from trucks. Many manufacturers and fleets say they prefer a national standard for emissions because trucks so often move across state lines, and varying rules present challenges to their business. The EPA’s last round of nitrogen-oxide rules for commercial trucks were developed in 2000, and it took about a decade for those rules to be fully implemented. “It’s definitely about time,” said Bill Wehrum, assistant administrator of the EPA’s Office of Air and Radiation. “The world has changed in a lot of ways over those 20 years. One thing we know is that these vehicles can be made cleaner, lower emitting.” The EPA’s push for new rules is only the beginning of a process likely to last years. The agency has no precise expectations on what new limits it will set or exactly […]