Local Authorities are being urged to consider real-world emissions, rather than Euro standards, to improve air quality.

AIR (Allow Independent Road-testing), the independent alliance set up to promote independent, on-road vehicle emissions testing says there are sizeable discrepancies between the best and worst-performing Euro 6 diesel cars.

According to data from Emissions Analytics, the difference between the cleanest and dirtiest Euro 6 cars has reached a record high.

Using the most recent tests, the cleanest 10% achieved an impressive 32 mg/km, yet the dirtiest 10% recorded 1,020 mg/km – a ratio of 32:1.

AIR says that city regulators should not base their air quality policies on the existing Euro standards and assume that Euro 6 diesel cars are cleaner than Euro 3, Euro 4 and Euro 5 ones.

It believes that city policy-makers will not be able to improve city air quality using Euro standards as the basis to keep very high emitting cars out of their cities.

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.”