Decision allows Colorado to enforce advanced clean car standards | Advocates applaud CO Attorney General Phil Weiser for challenging Trump administration’s attempted rollback and Governor Polis and then-Governor Hickenlooper for leading on clean cars

EPA returns authority to Colorado to limit pollution from cars and trucks

March 9, 2022

Danny Katz, CoPIRG, |
Travis Madsen, Southwest Energy Efficiency Project (SWEEP) |


[DENVER, CO] – To cut vehicle pollution and help clean our air, on Wednesday the Environmental Protection Agency (EPA) restored Colorado’s authority to implement tougher emission standards for new passenger cars.

The decision allows Colorado and the 16 other states (and Washington D.C.) who have adopted all or part of the Advanced Clean Cars program to move forward and enforce the rules. The move also suggests that EPA would be likely to issue a similar waiver for Colorado to enforce tougher emission standards for medium- and heavy-duty trucks, if the state adopts Advanced Clean Truck standards at the Air Quality Control Commission – a step the state has identified as important for protecting Colorado’s climate and improving public health. Advocates are asking the Polis administration to complete adoption of that policy this year, in 2022.

The EPA action finally resolves the Trump administration’s multi-year attempt to roll back federal vehicle emissions and mileage rules and block states from setting stronger vehicle tailpipe emissions standards. the Southwest Energy Efficiency Project (SWEEP), Healthy Air & Water Colorado (HAWC), and the Colorado Public Interest Reseawrch Group (CoPIRG) applauded Attorney General Phil Weiser for his part in securing this victory including joining a coalition of attorneys general and cities, including Denver, challenging the Trump administration’s effort. The groups also applauded then-Governor Hickenlooper and Governor Polis for taking the initiative to adopt tougher vehicle emission standards for Colorado in 2018 and 2019.

“Transportation pollution is Colorado’s largest source of global warming emissions, and it puts the health of all Americans at risk,” said Danny Katz, CoPIRG Executive Director. “Letting states set vehicle emission standards that support our clean air and climate goals is not only the right thing to do, but it will also help bolster the market for cleaner cars, benefiting all Coloradans. I’m glad Colorado Attorney General Phil Weiser stood up to attempts to roll back our clean air efforts in Colorado and then-Governor Hickenlooper and Governor Polis adopted these important clean air programs years ago.”

“Governor Polis did the right thing when he championed zero emission vehicle standards at the very beginning of his first term,” said Travis Madsen, Transportation Program Director at SWEEP. “With today’s EPA action, Colorado can now move forward and use the full power of the Clean Air Act to clean up tailpipe pollution. Everyone in the state will benefit from cleaner air and less climate change – and we’ll collectively save billions of dollars by switching from dirty, inefficient, and costly gasoline to clean electricity.”

“Pollution from transportation is a major contributor to Colorado’s poor air quality, which leads to both short and long term health consequences for Coloradans. Health experts agree that exposure to these pollutants can result in increased risk of exacerbating respiratory illnesses like asthma, and developing or complicating cardiovascular diseases, Alzheimer’s, or stroke,” said Sabrina Pacha, Director of HAWC. “Now that the EPA has restored Colorado’s right to enforce more stringent passenger vehicle emissions standards, the next step for Colorado is to address pollution from bigger vans and trucks by quickly adopting the Advanced Clean Trucks Rule. We need action to reduce pollution from all kinds of tailpipes to help clean up our air and protect our health.”

“We hope that Governor Polis will continue leading on vehicle emissions by adopting tougher emission standards for medium- and heavy-duty trucks as soon as possible,” Madsen concluded.


Vehicle tailpipes are a major source of health harming air pollution and are the single largest contributor to greenhouse gas emissions in Colorado. In 2021, Denver and the north Front Range experienced a record-breaking ozone pollution season.

Moving forward with clean vehicle standards will have major benefits for all Coloradans.

  • Advanced Clean Car Standards will save Coloradans on the order of $1 billion on gasoline and vehicle maintenance for new vehicles purchased through 2030. Further, the standards will prevent at least three million metric tons of global warming carbon dioxide pollution, and more than 300 tons of health-threatening ozone precursor pollution.*
  • If adopted, Advanced Clean Truck Standards would deliver more than $20 billion in benefits for Colorado through mid-century, according to an analysis commissioned by the Colorado Energy Office. That includes more than $6 billion in savings on fuel and maintenance for medium- and heavy-duty truck owners; a 45 percent reduction in climate-changing carbon dioxide pollution from these vehicles, and a 90 percent reduction in dangerous soot- and smog-forming pollution.

*These figures represent the benefits of only the Zero Emission Vehicle portion of the Advanced Clean Car Standards. Additional benefits, including billions of dollars in fuel savings and the prevention of tens of millions of tons of global warming pollution, could be attributed to the Low Emission Vehicle portion of the standards, compared to the Trump Administration’s unsuccessful proposal to roll back vehicle mileage and emission standards. However, we have not calculated those numbers precisely.


The Colorado Public Interest Research Group (CoPIRG) is an advocate for the public interest. They speak out for a healthier, safer world in which we’re freer to pursue our own individual well-being and the common good.

The Southwest Energy Efficiency Project (SWEEP) is a public interest organization promoting greater energy efficiency in Arizona, Colorado, Nevada, New Mexico, Utah, and Wyoming.

Healthy Air & Water Colorado (HAWC) is a nonprofit organization that elevates the voices of health professionals to promote policies that address the health impacts of climate.