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TNO publishes overview with details of diesel cars tested from 2010 to 2015

TNO calls on authorities and manufacturers to cooperate to reduce real-world NOx emissions • 10 Mar 2016

Today the Dutch research organization TNO published an overview of test results and extensive details of all Euro 5 and 6 diesel cars tested by TNO in recent years on behalf of the Dutch Ministry of Infrastructure and the Environment for real-life NOx (nitrous oxide) emissions.

Whereas to date TNO had published the results in an anonymized way, the results in this report are presented with reference to both make and model. The test results presented in the report contain elements not previously published, yet are fully consistent with earlier publications. The test procedures employed are also detailed and the results accompanied with general and specific comments to help interpret the results.

No verdict on 'manipulation software' or acceptable control strategy

From the detailed data per vehicle no conclusions may, or should, be drawn other than that they are indicative of the real-world emissions of that specific vehicle. TNO's current tests are neither suitable nor intended for giving a verdict on the precise cause of the differences in emission as measured in the official type approval tests and on the road. The results of the test can therefore not be used to ascertain whether any so-called 'manipulation software / defeat device' is employed or a control strategy of the engine management system that is permitted by type approval legislation.

Different manufacturers have provided explanations concerning the test results for the purpose of this publication. These have, in part, been incorporated as a footnote or comment for the results presented. TNO regards this information as technically plausible, but has not verified the statements and does not give any judgement on the extent to which explanations provided are acceptable in the light of the emission regulation.

General view: factor 3-5 times more NOx on the road

In daily use Euro 5 and 6 diesel cars emit much more NOx than during the type approval test on the roller bench. The detailed results now published substantiate the general view described by TNO in a number of reports in recent years. On average the vehicles tested in real-world situations emit 3 to 5 times more NOx than in the type approval test. In extreme situations, such as strong acceleration or driving at high speed, this factor may be 10 to 20.

Effective methods for NOx reduction already exist

It is technically feasible to reduce NOx emissions in practice using existing methods. The results of a number of vehicles show that a good combination of the various reduction methods that exist can produce a real-world emission performance that does come close to the type approval value. So no new technology has to be developed to achieve lower real-world NOx emissions. However, the existing technology must be better accommodated in the development of new or modification of existing models and diesel engines.

Decisive for better air quality

This conclusion and the results as a whole have motivated TNO to work together with the authorities and manufacturers to develop a better and more realistic system to determine and enforce real-world emissions. This will have significant benefits for air quality, especially in Europe’s urban areas. TNO is keen to bring in its expertise in this field to help work authorities and manufacturers in making the necessary advancements. TNO sees a role in this for the SEMS system it has developed to cost-effectively measure real-world emissions during normal vehicle use.

Emission factors

Under government supervision, national emission factors are established annually for road vehicles on the basis of the TNO measurements of real-world emissions. These emission factors are used to assess air quality, determine the total national emissions and estimate the effects of measures. These emission factors fully incorporate the major discrepancy identified by TNO between the real-life NOx emissions and the values in the type approval test, thereby offering a realistic picture of the actual situation.

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