California regulators approved a set of greenhouse gas regulations for trucks yesterday that deviate from the Trump administration, setting up a potential legal conflict.

The California Air Resources Board (ARB) voted unanimously to adopt emissions standards for heavy-duty trucks starting with the 2020 model year.

The rules are largely parallel to Obama-era federal standards adopted by U.S. EPA and the National Highway Traffic Safety Administration in October 2016. But they also seek to preserve California's authority to regulate emissions from two sectors that the Trump administration has backed away from. That could lead to legal conflicts.

State regulators said they were sticking to the Obama-era regulations for glider kits, or truck frames designed to hold refurbished engines, because the kits allow trucks to release copious amounts of nitrogen oxides and particulate matter—four to 40 times as much NOx and 50 to 450 times as much particulate matter as newer models, according to U.S. EPA testing. "That's a no brainer," board member Dan Sperling said. "It's embarrassing what's happening in Washington."

Under Trump, EPA proposed exempting glider kits from the truck rules in November 2017 on the grounds that they lack powertrains and are not "motor vehicles." The proposal came in response to a July petition from Fitzgerald Glider Kits, a Tennessee-based glider manufacturer that hosted a campaign event for Donald Trump when he was running for president, and two other companies (E&ENews PM, Dec. 4, 2017). Public comment on the proposal to repeal the glider rule ended last month.

Glider sales have been rising rapidly, from 1,000 sold nationwide in 2010 to 10,000 in 2015. The federal rules would limit sales of glider kits to 300 per year. California's adoption of the glider rule is "more symbolic than anything else," given that no gliders are produced within the state, said the manager of ARB's mobile source division, Kim Heroy-Rogalski. "We weren't able to get Tennessee's support ... and that's where this is happening."

California also approved its own version of federal regulations covering truck trailers, the other part of the federal regulation that EPA is reconsidering. If EPA rescinds its trailer regulations, ARB staff said they would propose adjusting a separate state trailer rule next year to cover more types of vehicles. California is maintaining its own trailer rules until 2020, which apply to a subset of those that will be regulated by the federal ones and apply to fleet owners rather than manufacturers.

California is also departing from the federal rules by making plans to conduct its own enforcement. Under previous versions of the standards, California accepted manufacturers' federal certifications as evidence of compliance, a practice known as "deemed to comply." Truck manufacturers represented by the Alliance of Automobile Manufacturers at yesterday's hearing said they opposed that move, although they supported the adoption of the glider rule.

Agency staff yesterday did not address the potential legal issues that could stem from deviating from the federal rules. Under the Clean Air Act, California can receive a waiver to implement its own rules, which are stricter than the federal standards. But that authority has been questioned by the Trump administration.

California, EPA and NHTSA are currently in talks over the fate of the Obama-era fuel economy standards for passenger vehicles from model years 2021 to 2025. State officials have expressed fear that EPA could refuse to issue waivers for California to pursue standards for future model years, or rescind the current waiver for the existing standards, which 13 other states have also agreed to (Climatewire, Jan. 26).

A vehicles expert on the environmental side said in an interview that California would likely need a waiver to conduct its own enforcement of the heavy-duty rules, but possibly not one to implement the glider and trailer rules.

"If EPA says they don't have the authority, then why does California need their permission?" said Don Anair, research and deputy director of the Union of Concerned Scientists' clean vehicles program. "It's uncertain until these things kind of get dealt with in court, in some sense."

On the federal level, the full package of rules is projected to avoid 1.1 billion metric tons of carbon dioxide emissions by 2027 and are scheduled to gradually increase in stringency from 2018 through 2027 through standards for tire resistance, tire inflation and pressure, and aerodynamic technologies. Within California, the standards are expected to reduce carbon dioxide by 207.6 million metric tons through 2050, the equivalent of reducing diesel fuel use by 20 billion gallons.

Reporter Camille von Kaenel contributed.

Reprinted from Climatewire with permission from E&E News. E&E provides daily coverage of essential energy and environmental news at