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European Parliament votes to phase out conformity factor for new car emissions under real driving conditions by Sep 2022

As of September 2022, new cars must meet EU limits on NOx emissions under real driving conditions to comply with air pollution limits, the European Parliament has voted.

Data on car emissions such as NOx had been obtained through laboratory tests. The EU is the first region in the world to use real driving emissions (RDE) tests to measure such pollutants emitted by vehicles while driven on the road. However, emissions from these vehicles in real-world driving conditions tend to be significantly higher.

To address technical uncertainties regarding measurements obtained through Portable Emission Measurement Systems (PEMS), which measure emissions from engines while they are being used, the Commission introduced the “conformity factor”, which allows for higher emissions under real driving conditions to take into account a margin of error.

With these exemptions, cars were allowed to emit 2.1 times over the legal NOx limit of 80 mg/km (hence up to 168 mg/km) until the end of 2020, and 43% more (up to 114 mg/km) with no set end date. The conformity factor was particularly useful for diesels.

European NGO Transport & Environment had shown that conformity factors were neither needed nor justified: out of 307 Real Driving Emission (RDE) test results from Euro 6d-temp and 6d diesel (the most recent engines), 87% of the cars emitted below 80 mg/km of NOx. New testing commissioned by the European Commission further confirms these findings.

To reduce NOx emissions, Parliament now wants the conformity factor currently in place to be annually lowered, based on assessments by the Joint Research Center. After being immediately lowered from 1.43 to 1.32, it should be gradually reduced and cease to apply by 30 September 2022, after which only the raw data from tests carried out under real driving conditions would be used to determine compliance with EU emission limits.

The report also asks that the Commission establish by June 2021 more stringent requirements for the portable measuring equipment to be used for RDE tests.

Today’s outcome is based on a broad agreement between the political groups. We have to be realistic about the discrepancy between emissions measured in laboratories and those measured in real-driving conditions by taking into account statistical and technical uncertainties linked to these measurements. At the same time, it’s important to show ambition by gradually lowering the value for the conformity factor through annual downward revisions, based on the scientific assessments of the Joint Research Center.

—Esther De Lange, Parliament’s rapporteur on the file

Parliament is now ready to start negotiations with EU member states to agree on final rules.

Background. According to the 2019 Air Quality Report by the European Environment Agency, air pollution led to more than half a million premature deaths in 2016 and is the number one environmental cause of premature death in the EU. As passenger cars produce 40% of total EU NOx emissions, they are a significant source of air pollution, especially in urban areas.

Emission measurements in the automotive sector were the subject of an EP inquiry committee (EMIS), set up in 2016 after the diesel scandal.



Good to see that fiddle finally going.

Next up as far as I am concerned is to end the fake zero emissions rating for BEVs, which ignores emissions in producing the electricity and the excess inbuilt emissions cost of making the batteries.

Proper math is at the heart of proper policy, and big battery BEVs in particular are hiding a lot under their skirts.


Volvo has come out with a way to measure true EV lifetime emissions.

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