While this Comment argues that the United States has a far stronger approach to regulating emissions from light-duty diesel vehicles than Germany, the U.S. approach is not perfect. Because emissions test parameters are public knowledge, automakers can design their emissions control devices 'to the test.' For example, the VW 'eco-diesel' family of vehicles had a software device that controlled emissions to the legal limits for the first thirty minutes that the vehicle ran but then gradually stopped working as the engine continued to run. This is likely because the federal emissions testing procedure used in the United States is approximately twenty minutes long, thus providing an opportunity for VW to evade notice of its practices for seven years.
Alexandria E. Pierce,
If It Ain't Broke: The Case Against "Rolling Back" Vehicle Emissions Regulations in the United States,
Emory Int'l L. Rev.
Available at: https://scholarlycommons.law.emory.edu/eilr/vol33/iss4/5