EPA Imposing Stricter Emission Standards

The Environmental Protection Agency (EPA) will soon enforce new emissions standards for a wide range of heavy-duty vehicles. 

The new rules, announced in a Jan. 24 Federal Register notice, aim to lower nitrogen oxide (NOx) emissions, along with other air pollutants, starting with model year 2027. The rules themselves will take effect March 27. 

Under the current standards, the NOx emission threshold for all heavy-duty engines (HDE) is 200 grams/horsepower-hour. That threshold will plummet to 35 milligrams/horsepower-hour (mg/hp-hr) for model years 2027 and beyond, according to a table in the notice. 

One exception is for a “low load cycle,” which didn’t previously have an emission standard. However, the new rule establishes a benchmark of 50 mg/hp-hr. 

In the same table, the EPA also notates emissions standards “with in-use compliance allowance,” meaning the thresholds are a bit higher when the agency is evaluating engines after they’ve been in use on the road. For that, the new NOx emission limits will be 50 mg/hp-hr for everything but low load cycles, which will be 65. 

Expanded Life Period 

In terms of “useful life period,” those standards are also being updated. Currently, the spark-ignition HDE has a useful life period of 110,000 miles or 10 years. That period is being increased to 200,000 miles, 15 years or 10,000 hours. 

The light HDE has a current period of 110,000 miles or 10 years, which will increase to 270,000 miles, 15 years or 13,000 hours. The medium HDE currently has a period of 185,000 or 10 years; that is being updated to 350,000 miles, 12 years or 17,000 hours. 

The heavy HDE’s useful life period is currently 435,000 miles, 10 years and 22,000 hours; that is being increased to 650,000 miles, 11 years and 32,000 hours. 

Under the new rules, emissions-related warranties will be extended “two to four times longer” than the current requirements. 

“We estimate that the final rule will reduce NOx emissions from heavy-duty vehicles in 2040 by more than 40 percent; by 2045, a year by which most of the regulated fleet will have turned over, heavy-duty NOx emissions will be almost 50 percent lower than they would have been without this action,” the notice stated. 

The proposed rule was published in the Federal Register on March 28, 2022, which received more than 260,000 comments, according to the Jan. 24 notice. 

The notice also made it clear that the agency is eyeing more regulatory action for the industry. 

“As the heavy-duty industry continues to transition to zero-emission technologies, EPA could consider additional criteria pollutant standards for model years beyond 2027 in future rules,” according to the notice.