The Dieselgate scandal, which broke in September 2015, exposed the unlawful activities of the Volkswagen group in “cheating” laboratory emissions tests through the installment of illegal emissions control devices in nearly 11 million diesel vehicles worldwide.
These “defeat devices” detect when vehicles undergo emissions testing in a lab setting and temporarily alter the engine’s performance to reduce NOx emissions, making the cars appear compliant with environmental regulations. Under real-world driving conditions, however, these Volkswagen vehicles would emit up to 35 times the legal limits.
Additional testing revealed that virtually all diesel vehicles across all manufacturers were producing excess emissions on the road, and in the years to follow, legal cases citing real-world emissions measurements resulted in substantial fines. Dieselgate prompted stricter regulatory frameworks and accelerated the shift toward more stringent emissions standards and zero-emission fleets, but the problem of excess emissions is not yet resolved.
Through continued real-world data collection by TRUE in cities across Europe, the ICCT has estimated that a large majority of vehicles with suspected prohibited defeat devices, across all manufacturers, are still driven in Europe and the United Kingdom today.
- 16 million show suspicious emissions, consistent with likely use of a prohibited defeat device
- 11 million show extremely high emissions, indicating almost certain use of a prohibited defeat device
