Consultant report

Strengthening the regulation of defeat devices in the European Union

Although the language in the U.S. and EU regulations on vehicle emissions testing prohibiting defeat devices, and defining exemptions or exceptions, is very similar, the regulations have been implemented quite differently. Consequently, similar real-world emissions control strategies have been found illegal in the United States but not in European Union.

One reason for this discrepancy is the extensive supplemental documentation that the U.S. regulatory agencies have issued to clarify and guide the implementation of the regulation. The U.S. guidance also explicitly puts the burden on manufacturers to prove they are not using a prohibited defeat device. This type of guidance is missing in the EU system, and the lack of guidance has contributed to inconsistency and uncertainty in how the regulations are to be enforced.

There is an opportunity to improve the language of the defeat device prohibition through the new type approval framework regulation recently proposed by the European Commission, which is now being evaluated by the European Parliament and the European Council. The ICCT commissioned Défense Terre to analyze the U.S. regulation and associated guidance documentation and propose areas where the type approval framework text could benefit from improved language. The resulting legal brief includes a discussion of the U.S. regulation as well as specific recommendations for how the type-approval framework proposal could be amended to more effectively prevent manufacturers’ use of defeat devices.

ICCT staff contacts: Rachel Muncrief,; Peter Mock,

Vehicle testing