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Norwegian/Finnish studies find Euro 6 cars exceeding NOx and CO2 type limits in real-world conditions; below on PM

Emission measurements conducted by Institute of Transport Economics in Norway, in collaboration with VTT in Finland, show that new Euro 6 cars with diesel engines are struggling with NOx emissions well in excess of regulatory type limits when in real traffic.

Since 2011, TØI and VTT have conducted emission measurements of 12 heavy vehicles with Euro VI engines, and seven Euro 6 diesel cars. In addition, they measured emissions from several gasoline vehicles (Euro 5 and 6) and Euro 5 diesel vehicles. All vehicles were tested in laboratory under conditions that as far as possible should correspond to the actual use of the vehicles.

Figure 1 - Emissions from diesel cars (at type app
Comparison between limit values for NOx, PM and CO2 from EU type approval regulations (black clouds) to emissions in “real life” city traffic from the average Euro 6 diesel passenger car on the Helsinki city cycle. Measured at +23 °C (red clouds) and -7 °C (blue clouds). The size of the red and blue clouds indicate the difference in emissions from the emissions in the type approval test (NEDC). Figure credit: Institute of Transport Economics. Click to enlarge.

Based on the measurements of the 12 heavy vehicles with new Euro VI approved engines and seven Euro 6 approved cars with diesel engines, they drew two clear conclusions when it comes to exhaust emissions:

  • All the tested heavy vehicles with Euro VI engines have very low emissions of NOx and PM in real traffic. The tested NOx and PM emissions were less than 1/10 of that from previous generations of city buses and other heavy vehicles with Euro VI engines, more or less regardless of the driving cycle used when testing.

  • Euro 6 type-approved private cars with diesel engines have 4-20 times higher emission of NOx in city traffic and during cold weather than the type approval limit value (0.08 g/km). The average emission of NOx from the tested Euro 6 private cars with diesel engines was also about four times higher than the average emission from the tested city buses and heavy vehicles with Euro VI engines.

One caveat is that no heavy vehicles have yet been tested in cold weather conditions. Although the researchers believe that heavy vehicles with Euro VI engine will have low emissions of NOx even in cold test conditions, they will test this during the winter 2015/2016.

We notice that new private cars with diesel engines generally have trouble complying with the limit values for NOx from the type approval, when used in real life city traffic. The type approval of light vehicles is conducted by driving the NEDC driving cycle (New European Driving Cycle). The NEDC driving cycle has low acceleration levels and provide emission values of NOx and NO2 which is lower than emissions when driving in real city traffic, and often significantly lower than emissions when starting and driving in cold weather conditions (-7 °C).

—TØI Report 1407/2015

In real traffic, Euro 5 diesel cars and the seven tested Euro 6 passenger cars with diesel engines generally have low emissions of particulate matter (PM). The PM limit value for Euro 6 approval is significantly higher than what the researchers measured from new Euro 6-approved diesel vehicles under all driving conditions. In other words, new diesel cars have efficient and well-functioning particulate filters.

Modern heavy vehicles—including city buses with Euro VI engines—also have low emissions of NOxand exhaust particles (PM) for all types of test cycles. The reductions are more than 90% compared to the emissions from previous Euro V generations. Indeed, the researchers found that NOx emissions from the light duty vehicles exceeded those from the city buses.

Figure 2 - NOx emissions from Euro 6 diesel cars
New heavy vehicles with Euro VI approved diesel engines have very low emission of all types of local emissions. NOx emissions from new passenger cars with Euro 6 diesel engines under demanding city driving conditions is still a challenge for urban air quality. The emissions shown are typical for demanding city-driving for passenger cars and city-buses, respectively. Figure credit: Institute of Transport Economics. Click to enlarge.

For fuel consumption and exhaust emissions of CO2, the values from all kinds of new light vehicles are higher than what is measured in the NEDC cycle type approval testing. A car that has low CO2 emissions in type approval will have, as a rule, emissions ranging from 20-95% higher in real traffic. A car that has high CO2 emissions in type approval will have even higher emissions in real traffic. The low emission values from the type approval may give the impression that the cars are more environmentally friendly than they actually are, the researchers said.

The problem of harmful local emissions has more aspects than the discussion about fuel consumption, and petrol versus diesel. The real challenge is the emission of PM and NOx from older vehicles, as well as NOx and NO2 emissions from new Euro 6 diesel cars in real traffic and during cold weather conditions.

—TØI Report 1407/2015

The study was funded by the Norwegian Public Roads Administration, as part of the “EMIROAD” program.


  • TØI Report 1407/2015. Emissions from new vehicles - trustworthy? Authors: Rolf Hagman, Christian Weber and Astrid H. Amundsen

  • TØI Report 1405/2015. Emission from vehicles with Euro 6/VI-technology. Authors: Christian Weber, Rolf Hagman, Astrid H. Amundsen

  • TØI Report 1259/2013. Exhaust emissions from vehicles with Euro 6/VI technology. Authors: Rolf Hagman and Astrid H. Amundsen


Account Deleted

This is creasy. More mass murder. Which cars are we talking about from which manufacturers? We need to know so that a criminal investigation can begin. Also note the date of this study. TØI Report 1407/2015 which is before the VW's dirty diesel scandal broke.

Dr. Strange Love

Henrik. I have a feeling that the heavy duty vehicles in the study are outfitted with UREA/SCR while the LDVs are not outfitted. UREA is the factor here.


Or as Transport Enviroment stated in the report "Don't breathe here" that even when carmakers fit SCR they often configure the system to be ineffektiva to avoid either needing a large storage resovoir or requiring the driver to refill between sevice intervall...

James McLaughlin

In the US, the NOx limits for heavy vehicles are in terms of grams of NOx per brake horsepower hour. I thought the Euro limits were analogous, grams per kWh. This article says grams per km? I need to check, this does not see right for heavies...

Account Deleted


I think you are right. That urea solution seems to be the only thing that works for diesels but that is just my impression from reading the experts opinions. I am not technical enough to actually know what will work to make diesel engines less dirty. I think the urea solution is too complicated and costly for consumer cars. People do not want to remember to fill another tank with some pretty nasty stuff that they better not spill on their skin. I think VW just might have killed diesels for consumer vehicles forever.


More good reasons to partly and/or fully electrify small and large vehicles?

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