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EPA introduces stringent new truck engine emission rules

Improvements should result in fewer deaths, fewer missed school and work days

The EPA on Tuesday released its final rules on reduced NOx and particulate emissions for heavy-duty vehicles such as semi-trucks, buses and other commercial vehicles. They're the first new smog rules for big trucks in more than 20 years, according to the agency.

The EPA predicts significant improvements in NOx emissions. Through 2045, it expects those emissions to be reduced by 48%. Particulate emissions, volatile organic compounds (VOC) and carbon monoxide emissions will also go down by 8%, 23% and 18% respectively. These emissions are typically quite high from commercial vehicle engines, especially diesels. NOx emissions contribute to smog, and smog as well as particulate emissions have harmful effects to respiratory health.

As such, reducing them can cause major health improvements. The EPA expects 2,900 fewer premature deaths, 6,700 fewer hospital and emergency room visits and $29 billion in annual net benefits, including fewer missed work days and school days. 

The new regulations require not just significantly reduced emissions for both spark-ignition (i.e. gasoline) and compression-ignition (i.e. diesel) engines, but for longer-lasting emissions equipment and better support for maintaining them. The rules apply to engines starting with the 2027 model year. However, the new rules do not address greenhouse gas emissions such as carbon dioxide, which would affect climate change. The organization still plans new rules for those.

The new emissions targets announced Tuesday are substantially more stringent. NOx emissions have to drop from 200 mg per horsepower-hour to 35 mg for spark-ignition engines, and 50 mg for compression-ignition engines. That's for cruising and acceleration testing. New requirements are also going into place for "low-load" conditions such as idling and stop-and-go traffic, as part of the EPA's expanded testing. Spark-ignition engines will have to hit 50 mg, and compression-ignition engines will have to reach 65 mg.

The EPA is also not allowing for special credits from the implementation of electric trucks in order to prevent that being used as a loophole to continue building higher-emissions combustion-engine vehicles.

The EPA is also requiring engine manufacturers to provide emissions equipment that can last the lifetime of the engines, in order to reduce the incentive to defeat emissions equipment after failures during the life of the vehicles. Currently, the lifetime estimates for the different classes of engines are fairly low at 110,000 miles/10 years for spark-ignition engines to 435,000 miles/10 years/22,000 hours for the heaviest-duty compression-ignition engines. These will increase to 200,000 miles/15 years/10,000 hours and 650,000 miles/11 years/32,000 hours respectively. Other lighter duty compression engines fall between those extremes.

Warranties for the emissions equipment must increase accordingly, too, in order to incentivize maintaining this equipment. At the low end, spark-ignition engine equipment must be warrantied for at least 160,000 miles, 10 years or 8,000 hours, rather than the current requirement of 50,000 miles or 5 years. At the high end, the heaviest duty compression-ignition equipment warranties must improve from 100,000 miles or 5 years to 450,000 miles, 10 years or 22,000 hours. Furthermore, serviceability of the equipment needs to be improved with better documentation available to owners, operators and independent mechanics.

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