More stringent standards are needed to reduce nitrogen oxide, or NOx, emissions from heavy-duty trucks, buses and other diesel vehicles, the Environmental Protection Agency said Tuesday, but it rejected calls from a coalition of state governments, air quality districts and environmental groups to speed up the timeline for enacting new regulations.

A group of 20 petitioners that includes state and local environmental agencies in California, Connecticut, New York, Massachusetts, Rhode Island and Washington urged the agency to speed up the rulemaking process to develop ultra-low NOx emissions standards for on-road heavy-duty engines so that they would go into effect with 2022 model year vehicles.

The agencies wanted the EPA to issue the notice of final rulemaking by Dec. 31, 2017. Such a move would launch the regulatory process after President-elect Trump takes office, but not without an expected change of course for the EPA.

Trump has nominated Oklahoma Attorney General Scott Pruitt to head the EPA. Pruitt, who questions the degree and extent of global warming and is part of a coalition of state attorneys general suing to block the EPA’s Clean Power Plan, is less likely than current EPA administrator Gina McCarthy to pursue aggressive environmental regulation.

The EPA said a condensed timeframe for launching new NOx standards wasn’t feasible, but added that it will “initiate the work necessary to issue a notice of proposed rulemaking with the intention of proposing standards that could begin in model year 2024.”

“This timeframe is consistent with the lead time requirements of the Clean Air Act and is aligned with a milestone implementation year for the EPA heavy-duty Phase 2 Greenhouse Gas program,” the EPA said.

In August, the EPA and the National Highway Traffic Safety Administration issued new greenhouse gas standards that will force manufacturers to reduce carbon emissions from a wide range of commercial trucks, buses and cargo vans in three phases.

“Phase 2 includes technology-advancing, performance-based standards that will phase in over the long-term, with initial standards for most vehicles and engines commencing in model year 2021, increasing in stringency in model year 2024, and culminating in model year 2027 standards,” according to the EPA memo.

In its response to the petitioners, the EPA said it plans to work closely with the California Air Resources Board to consider “the development of a new harmonized federal and California program to reduce NOx emissions from heavy-duty on-highway engines and vehicles that could be adopted not only by the EPA, but also by CARB, in order to maintain a 50-state program.”

The petitioners pushing for the tighter NOx standards include Southern California’s South Coast Air Quality Management District and the state’s San Joaquin Valley Air Pollution Control District. Both agencies regulate air quality in some of the nation’s worst areas for pollution.

The Union of Concerned Scientists, which supported the petition, said it’s been more than 16 years since the EPA last revised its NOx standards for heavy-duty trucks.

“Heavy-duty trucks, which are the main producers of NOx emissions, are a key contributor to ozone-related problems and public health concerns,” said Don Anair, research and deputy director for the Clean Vehicles Program for the Union of Concerned Scientists.

During the Phase 2 rulemaking process, the EPA said it had received concerns from trade groups, truck makers and engine manufacturers urging the agency to “consider the relationship with CO2 and NOx before setting lower NOx standards.”

The American Trucking Associations said that as an industry working across state lines, it believes air quality and emissions regulations should be done “exclusively at the federal level and that states should not be allowed to create de facto national standards outside of the federal regulatory process.”

“ATA has a long track record of improving the environment, from our work with EPA’s SmartWay Transport Partnership to our support of Phase 1 and 2 of EPA’s fuel efficiency rule for medium and heavy-duty trucks,” said Glen Kedzie, ATA’s vice president and energy and environmental affairs counsel.

“That said, the further ramping down of NOx emissions as envisioned by this petition will likely have a deleterious effect on our industry’s overall fuel economy. We believe any tightening of NOx standards for large trucks must consider these impacts, as well as the impact these technologies may have on engine cost and reliability,” Kedzie said.

Daimler Trucks North America will collaborate with the EPA, CARB and other stakeholders on future NOx regulations and “will work to ensure that such reductions do not jeopardize future CO2 and fuel economy reductions,” said Sean Waters, director of regulatory affairs and product compliance at Daimler.

Related: Trucking Industry Lawsuit Could Roll Back California Environmental Regulation

About The Author

Clarissa Hawes

Clarissa Hawes is a Trucks.com staff writer who covers trucking and freight. She is an award-winning journalist with over 10 years of experience covering the trucking industry. She can be found on Twitter: @cage_writer.

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