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All new diesel cars fail EU NOx emissions standards in real-world driving, says study

All new diesel-engined cars fail to meet EU standards in real-world driving for NOx emissions, research by the International Council of Clean Transportation – the environmental group which exposed the Volkswagen scandal - has shown.

The International Council on Clean Transportation (ICCT) found four manufacturer groups had average emissions more than 12 times above the Euro 6 diesel type-approval limit, with the highest emitting vehicle family having emissions 18 times the limit.

Petrol cars fared better, however, with all Euro 6 petrol models receiving a ‘good’ or ‘moderate’ rating.

The highest-emitting petrol Euro 6 vehicle family had approximately the same level of NOx emissions as the lowest-emitting diesel vehicle family.

The ICCT carried out emissions tests on more than 700,000 cars and 4,850 vehicle models, nearly all designed and built to Euro standards 3-6, across Europe. The initial dataset comprises samples collected in France, Spain, Sweden, Switzerland and the United Kingdom, and pooled together in the CONOX project, funded by the Swiss Federal Office for the Environment.

In London, for example, researchers used remote sensing technology to measure the emissions from more than 100,000 vehicles during a five-month sampling campaign that stretched from November 2017 through March 2018.

Measurements were made on a total of 45 days at nine locations throughout the Greater London area. 

All results have been put into a searchable database by the Real Urban Emissions Initiative (TRUE), which aims to bring transparency to the public debate on vehicle emissions and urban air quality.

The ratings system is based on a methodology developed by ICCT, and involves passing a beam of light through a car’s exhaust emissions from a sampling location on the road. Automatic number plate recognition technology is used to determine which model of car is being tested.

ICCT says this method of monitoring real-world vehicle pollutant emissions is difficult-to-impossible to cheat or game.

Cars are ranked in a three-colour rating system to indicate their real-world NOx emissions.

Green indicates less than 90 milligrams of NOx per kilometre, yellow indicates between 90 and 180mg/km and red for in excess of 180mg/km.

No Euro 6 standard diesel engine received a green rating, while BMW was the only top-selling brand to achieve a yellow rating for its diesel cars.

The study found that Euro 5 diesel families performed particularly poorly. All had NOx emissions at least twice the limit, and the worst had emissions 18 times the limit.

Nick Molden, chief executive of Emissions Analytics, which publishes a different emissions rating system called the Equa Index, told The Guardian the True rating is a “brilliant” screening tool and also good at monitoring pollution from cars as they get older.

However, he cautioned that True, which averages the same models across several years, will not show when the latest model has significantly cut its emissions. Molden highlighted a Mercedes-Benz model that improved significantly between 2014 and 2017.

“It went from quite dirty to really quite clean,” he added.



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  • Rob Bennett - 06/06/2018 12:39

    Though there will no doubt be some truth to the figures gained by TRUE I see flaws in their sampling methods as and I quote "The ratings system is based on a methodology developed by ICCT, and involves passing a beam of light through a car’s exhaust emissions from a sampling location on the road. Automatic number plate recognition technology is used to determine which model of car is being tested". The test is carried out at one point in the road and not whilst travelling on a real world test. Erroneous figures will easily be reached based on accelerator position, vehicle load, weather condition, etc. If you check a vehicle as it immediately sets off the emissions are higher than once moving and much higher than when the desired speed of travel is reached. Again the reference does not take into account whether a vehicle has been remapped or had a chip tuning box fitted, all of which can improve or make emissions much worse. Lets stop slaughtering diesel cars for their poor emissions and work to improve them, which is just a matter of time and technological gains. We don't have as yet a credible real world alternative to fossil fuelled vehicles. I can't wait until all the company cars are changed to electric by scared managers fearing they are not being "Green". How are we going to fuel and recharge these cars that average 3 to 400 miles a day. Currently they pull into a service station, refuel in 10 minutes and are once again on their way. 2 to 300 cars an hour are refuelled at service stations on main networks. Most places don't have a charging network and those that do cater for maybe half a dozen vehicles at most. How are we going to recharge 2- 300 vehicles an hour bearing in mind there are very few electric vehicles that achieve a decent charge in one hour.

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  • Greg - 06/06/2018 13:22

    Not sure of the point in this article. The salient fact was omitted until the final sentence which qualifies almost the entire piece. Most people accept that older diesel vehicles emit excess NOx - perhaps the qualification should be at the start or even in the title maybe ' Most older diesel vehicles fail new Eu Nox emission tests, whilst new vehicles are 'really quite clean'.

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  • giantpanda - 07/06/2018 08:48

    CO2 emissions can not be considered singly. Norms have also to take fine particles into consideration. So they can only be a compromise between the 2.

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  • Andrew Cree - 07/06/2018 10:36

    There's certainly an error with the methodology used by this group, as the BBC reported over a year ago that (at the time of the report) two vehicles cane in slightly under the NO emissions limits - if memory serves, one was a Mercedes, the other was certainly a Volkswagen. That data required modifying the car to capture the exhaust fumes and analyse those, so presumably far more indicative of "real world" driving data than passing a laser through the fumes as a vehicle passes.

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