Tampering. Deliverable D1.3

Emission legislation for motorised vehicles typically focuses on new models, who’s effect on air quality only slowly takes form due to the existing fleet’s inertia to change. Tampering with, or illegally modifying, emission control devices can substantially distort a fleet’s impact as only a few high emitting vehicles with improperly working/removed emission control devices can be held responsible for disproportionally high contributions to poor local air quality. This report documents an overview of what research has been done to date to estimate the impact of tampering, and to estimate its scale within the European Union. Whereas tampering with diesel particulate filters is mostly applied on light-duty vehicles, deactivating de-NOx systems like selective catalytic reduction systems generally occurs in the heavy-duty sector. Nonetheless, as SCR technology is deemed to become the reference in light-duty diesel vehicles, it’s only a matter of time before consumers try to bypass such systems. The impact of these measures are unambiguous, as a removed particle filter increased particle number emissions by a factor thousand, while heavy-duty de-NOx bypassing increases NOx emissions by a factor 4 to 20 for Euro VI technology