Defeat devices under the U.S. and EU passenger vehicle emissions testing regulations

The paper aims to illuminate a paradox: Volkswagen and other automakers have asserted that software managing the emissions control systems on some of their vehicles, which they acknowledge either is or would be considered an illegal defeat device under the U.S. vehicle emissions regulation, is either not a defeat device or not prohibited as such in the European Union, even though the language defining and prohibiting defeat devices in the U.S. and EU regulations is nearly identical.

The paper summarizes the relevant provisions of the current EU and U.S. regulations, reviews what is publicly known about the automakers’ positions with respect to those provisions, and contributes an independent engineering perspective where relevant. The intent is to provide context for evaluating proposals to reform the regulations governing passenger vehicle type approval and real-world testing in Europe. Such a summary spotlights ambiguities in the EU regulation as it presently stands—and potentially in any regulation patterned on it, as many national vehicle emissions regulations are.

Proposals to reform the EU regulation (or others patterned on it) should be scrutinized to assess the degree to which they would resolve those ambiguities. In particular, three questions should be asked: (1) whether and how proposed reforms would require manufacturers to disclose the presence of defeat devices as defined in the regulation; (2) what requirements would be imposed concerning how the listed exceptions to the prohibition on defeat devices must be claimed, evaluated, and approved or rejected; and (3) whether and how proposed new regulatory text defines key terms and concepts such as normal operating conditions, normal vehicle operation and use, and emissions control system.

Vehicle testing