As the football saying goes: “Performance on the field is what matters”. When measuring emissions, the same applies to performance on the road. For this reason, according to the Euro 6d-TEMP standard and the even more far-reaching Euro 6d standard, the lab measurements according to the WLTP are supplemented by the so-called RDE test (Real Driving Emissions). Pollutant emissions (including nitrogen oxide and particles) are measured in vehicles directly on the road and compliance of limits with conformity factors is checked.
The additional RDE test is intended to allow the pollutant emissions to be tested under real driving conditions. In contrast to a lab test, the RDE test does not follow a set driving cycle. Instead, the emissions are tested under real driving conditions with legally defined permissible ambient conditions. For the RDE test, the vehicles are equipped with a so-called PEMS (Portable Emissions Measurement System) device for mobile emissions measurement (for details, see chapter “Under the microscope: The PEMS measurement”).
For vehicles undergoing an RDE test as part of the Euro 6d-TEMP or Euro 6d emissions standard, the emissions limits of the Euro 6 standard plus so-called conformity factors must be complied with. For nitrogen oxide, this conformity factor in Phase 1 of RDE (new passenger car approvals are possible up until 31 December 2020) is 2.1, for the particle number 1.0 +0.5. The value of 0.5 for the particle number corresponds to a measuring tolerance of 0.5 which illustrates variations in the measurement technology. The vehicle must technically comply with the particle limit of 6*1011 per km in an RDE drive.
In RDE Phase 2 (Euro 6d), which applies to new models from 1 January 2020 and/or to all newly approved cars from 1 January 2021, the factor for nitrogen oxide is 1.0 + 0.43, the 0.43 value corresponds to the measuring tolerance. On December 13th, 2018, the General Court of the European Union (EGC) made a first decision concerning the power of the EU Commission to adopt specific provisions on RDE tests. It is currently unclear whether the European Commission will appeal this ruling to the European Court of Justice (ECJ). If the judgment becomes final, it may lead to a fundamental reassessment of the conformity factors. The legally defined permissible range for an RDE test covers a wide field of application, e.g. it allows speeds of up to 160 km/h, temperatures down to -7 °C and driving in mountainous terrain.
The limits with the above-mentioned conformity factors are to be observed. Since the limits have to be fulfilled under all possible combinations of the parameters, emissions in real-life customer operation are generally significantly below the prescribed limits.
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SOURCE: Daimler
