Diesel cars adhering to the latest environmental class legislation, Euro 6, release about five times as much nitrogen oxides in real mileage as is required by law. This according to a survey conducted by IVL Swedish Environmental Research Institute. In the study, exhaust emissions from more than 30,000 cars were measured in Gothenburg traffic.
– This confirms what we have previously feared, that even the latest diesel cars emit high levels of nitrogen oxides. Unfortunately existing legislation and emission controls have not had the intended effect, says Åke Sjödin, researcher at IVL Swedish Environmental Research Institute.
The measurements carried out in Gothenburg show that the latest Euro 6 emissions standard has brought about improvements. On average, emissions of nitrogen oxides in real driving conditions have decreased by about 60 per cent when Euro 6 is compared with previous Euro classes. For example the Volkswagen Euro 5 diesel cars rank among those with the highest emissions, while their Euro 6 cars are among those with the lowest emissions. Euro 6 trucks and buses also have significantly lower emissions than previous Euro classes.
– This can still be seen as a breakthrough. In the past, there has not been any real discernible change in emissions between Euro 2 and Euro 5 exhaust standards in real-life driving conditions. Now, we finally see a reduction in Euro 6 cars, although there is a long way to go before these will live up to the expectations created by the legal requirements, says Åke Sjödin.
However, many diesel cars with higher emissions are still driving on our streets. The study showed major differences between different brands, models and individual vehicles. NOx emissions are also higher at lower ambient temperatures, which is unfavourable for Sweden. For Euro 5 cars, there are roughly 60 per cent higher NOx emissions at 10-plus degrees Celsius than at plus 25 degrees.
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About the study
The study amassed large amounts of data. Using so-called remote sensing technology, exhaust gases from more than 30,000 passing vehicles were measured in real time. Just over six thousand were diesel cars and 90 per cent of these Euro 5 and Euro 6. These measurements were carried out at, among other places, the Tingstad Tunnel on European route E6 (the Gullberg Junction), and on Gibraltargatan in central Gothenburg. Information about driving conditions and vehicle data were also collected.
The study has been financed by the Swedish Transport Agency, the Swedish Environmental Protection Agency, the vehicle inspection company Opus and the IVL Foundation.
The results of IVL's measurements are also confirmed by the new version of the European emissions model HBEFA 3.3 (Handbook Emission Factors for Road Transport), published in the spring, which takes into account the higher emissions of nitrogen oxides by real-life diesel engines. IVL has been commissioned by the Swedish Transport Administration to be responsible for the updating HBEFA annually with statistics for Swedish road traffic. HBEFA 3.3 has now been implemented in the 2017 estimates for Sweden, delivered to the EU and the UN Climate Convention. This means that the national emission statistics must now be revised, including NOx emissions in many municipalities. The new calculations represent an increase of 6,000 tonnes of NOx emissions in Sweden.