Press release

Vehicle tests show dramatic variation in NOx emissions from modern diesel cars on new EU test cycle, with exceedances up to 15 times the current regulatory limit

Some automakers meeting diesel NOx emissions standards under more realistic driving conditions, while others lag badly.

The technologies to control emissions of nitrogen oxides (NOx) from modern diesel cars under realistic driving conditions already exist today. In some cases manufacturers are using them effectively to drive NOx emissions down to low levels, complying with the Euro 6 emission standard, which is scheduled to be introduced in the EU in 2017. But in others, NOx emissions are much higher — on average more than twice as high as the current regulatory limit, even under laboratory test conditions. This is the key finding from a report published today in Berlin by the International Council on Clean Transportation (ICCT), an independent research organization.

The study, which analyzes the results of emissions tests performed by Europe’s largest car club, Allgemeiner Deutscher Automobil-Club (ADAC), covers 32 Euro 6 diesel passenger cars from 10 different manufacturers featuring different types of exhaust aftertreatment technologies. The findings come at a time when the European Commission is about to propose “conformity factors”, i.e., emissions limit multipliers that will apply to the new on-road vehicle emissions tests. These conformity factors will have a large impact on the deployment of emissions control technologies, and thus on the “real-world” emissions performance of new diesel cars.

The vehicles were tested as part of the ADAC EcoTest, following the current legislative test procedure – the New European Driving Cycle (NEDC) – as well as the Worldwide Harmonized Light Vehicles Test Cycle (WLTC), which is scheduled to replace the NEDC in the EU from 2017 on. All vehicles tested met the Euro 6 nitrogen oxide emission limit of 80 milligrams per kilometer (mg/km) in the NEDC. But only ten out of the 32 cars met the same limit in the more realistic WLTC.

“On average, the nitrogen oxides emission level in the new test cycle was more than double the Euro 6 limit value”, says Dr. Peter Mock, Managing Director of ICCT Europe. The highest emission levels in WLTC were found for a Volvo (14.6 times the limit), a Renault (8.8 times the limit) and a Hyundai (6.9 times the limit) vehicle. A BMW model had the lowest emission level (70 percent below the Euro 6 limit).

“The results indicate that the implementation of nitrogen oxides control technologies by a few manufacturers is delivering acceptable results over both cycles. Other manufacturers seem to be focusing on meeting emission limits over the current test cycle while neglecting real-world operating conditions”, says Dr. Vicente Franco, a researcher at the ICCT and co-author of the study.

In May of this year, the member states of the European Union decided to require on-road testing as part of the passenger car type-approval process. As a result of this decision, from 2016 on vehicle manufacturers will have to test exhaust emissions of new vehicles not only under laboratory conditions but also on the road using on-board emission measurement systems. On-road emissions are known to be higher than certification test values, so current discussions in Brussels now focus on determining the “conformity factor”, i.e., how much higher emissions are allowed to be during this on-road test than in the laboratory. These conformity factors will be enforced from 2017 on, after a 20-month pilot phase to introduce the new testing procedure.

Nitrogen oxides emissions (especially NO2) can have serious adverse health effects, causing major respiratory problems and leading to premature death. Diesel vehicles are the single largest contributor to total nitrogen oxides emissions in the EU. Especially in urban areas of Europe, measured NO2 ambient concentration levels are often higher than the legal limits, and some EU Member States, such as the UK and Germany, are already facing legal actions for persistent air pollution problems.

Contact: Peter Mock, +49 (30) 847129-102,

NOx emission performance over the NEDC and WLTC cycles for all 32 vehicles, by NOx control technology, vehicle segment, and manufacturer.

Vehicle testing