On Thursday, the U.S. Department of Justice announced the largest ever Clean Air Act penalty against a major engine maker, Cummins Inc., over accusations of emissions test cheating. The settlement with a total of nearly $1 billion in penalties is the result of a federal investigation dating back to 2016 that found the Cummins’ heavy-duty diesel engines used in trucks and buses used illegal defeat devices to circumvent U.S. emissions standards. The penalty includes not only the largest civil penalty in the history of the act but also a criminal penalty. The company was accused of using software to manipulate its engine performance during emission tests, which generated false test results and allowed increased levels of pollutants to come out of its vehicle’s tailpipes. The settlement includes a $14 million criminal penalty and a $75 million civil penalty. The company will also pay $176 million to settle claims from the U.S. Environmental Protection Agency (EPA) and other state and federal agencies. Additionally, Cummins pledged to invest $790 million into cleaner technologies as part of the deal. The settlement requires Cummins to develop and deploy diesel Particulate Matter (PM) and Nitrogen Oxide (NOx) reducing technology for engines and aftertreatment devices, setting rigorous emission standards that are expected to result in significantly cleaner air in many areas of the United States. In a statement, Cummins stated that the company had “worked hard to get this resolution behind us and to prove our ongoing commitment to environmental compliance and to innovate to become a leader in the space.” Cummins is one of several auto-parts manufacturers that have faced large fines over the past few years for using illegal emissions-cheating technology in their products. The settlement serves as a reminder of the importance of compliance with environmental regulations, especially from major manufacturers.