Cities can do much better than ‘Euro 6’ says AIR alliance

  • Difference between cleanest and dirtiest Euro 6 diesel cars at record high
  • Newly launched diesel car models emit 70% less on-road NOx than regulation
  • Cities can implement better policies now to improve air quality

AIR (Allow Independent Road-testing), the independent alliance set up to improve air quality by promoting independent, on-road vehicle emissions testing, has urged city authorities to use existing emissions data to immediately improve their air quality after sizeable discrepancies were found between the best and worst-performing Euro 6 diesel cars on city roads today.

According to data from on-road testing by Emissions Analytics (EA), the gulf between the cleanest and dirtiest Euro 6 cars has reached a record high. Their tests, using Portable Emissions Measurement Systems (PEMS), show that in May 2013 the cleanest 10% of diesels emitted 265 mg/km and the dirtiest 10% emitted 1,777 mg/km – a ratio of 7:1. Using the most recent tests, the cleanest 10% achieved an impressive 32 mg/km, yet the dirtiest 10% recorded 1,020 mg/km – a starkly worse ratio of 32:1.

City regulators currently base their air quality policies on the existing Euro standards and understandably assume that Euro 6 diesel cars are cleaner than Euro 3, Euro 4 and Euro 5 ones. However, while all cars sold are legally compliant and pass the laboratory ‘type approval’ test, the gulf between best and worst Euro 6 compliant cars, when tested on the road, is glaring.

Using on-road PEMS testing, the new standard for testing new car models launched after 1 September 2017, the average diesel car NOx emissions tested by EA shows a reduction of 55% between Euro 5 and Euro 6; falling from an average of 812 mg/km to 364 mg/km. While this reduction demonstrates progress in reducing NOx emissions the average Euro 6 car on-road NOx emissions level is still over 350% higher – or 4.5 times – the laboratory test level against which they were approved.

On-road testing by EA of six new diesel vehicles compliant with the EU Real Driving Emissions (RDE) legislation – also known as ‘Euro 6d-temp’ – sold for the first time since 1 September 2017 produced average NOx emissions of 48 mg/km, 40% below the previous in-laboratory limit and 70% below the current RDE limit. These test results show that the cleanest diesel cars emit similar levels of NOx as newer gasoline engines which average 36 mg/km in EA tests.

City policy-makers are unable to improve city air quality using Euro standars as the basis to keep very high emitting cars out of their cities. They are frustrated at having to choose to ban all diesel cars when some are much cleaner than others.

Massimo Fedeli, Operations Director of AIR, said: “As an independent not-for-profit alliance we can offer cities a way to fairly treat diesel cars and improve their air quality. We have licenced access to the on-road test data that cities can use immediately to improve their air quality. AIR is also working to ensure multiple test centres in Europe can use a voluntary CEN standard to increase testing to cover all cars entering cities in the EU. Emissions Analytics’ testing since 2011 will be compatible with this new standard to help cities treat each car and each car owner fairly now.”


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