A not-for-profit organisation of scientists and academics have launched an emissions ranking system to help identify the most and least polluting vehicles.

AIR (Allow Independent Road-testing) has unveiled the AIR Index to measures vehicle nitrogen oxide (NOx) emissions in real-world environments and away from laboratory settings.

New vehicle sales since 2015

New vehicle sales dipped dramatically in 2018 and early 2019 as a direct result of the 2015 VW diesel-gate scandal in the US, with consumers more hesitant to purchase diesel vehicles because of a lack of trust in the published emissions and efficiency data from manufacturers.

However, the release of the AIR Index is expected to raise consumer confidence in 2019, not least because many new models have been shown to be performing extremely well. Even manufacturers of large vehicles have achieved impressive results, such as the diesel engine Land Rover Discovery.

The index runs a traffic light system to judge the NOx emissions of models on sale.

NOx and particulate matter emissions are the two hot topics in the automotive industry and have been identified as the primary causes of localised pollution in cities. The index will offer a simple way to identify the best and worst performing vehicles on the road.

Provided consumers have good access to the results, 2019 could prove to be a much better year for car manufacturers, as long as the global economy remains stable.

AIR emissions rating traffic light system

Source: AIR Index, MarketLine

There is still a significant difference between the best and worst performing vehicles

AIR is yet to start testing all models on sale, but initial results for six vehicle models have been released for comparison.

This Independent testing has shown that there is a huge disparity between models on sale, some 2018 and 2019 model year vehicles are performing excellently, well below the levels of NOx that national regulators have set.

Contrary to popular opinion many modern diesel engines on sale are actually significantly less polluting than models that are four or five years older.

Testing from AIR is done using portable emissions testing devices and done predominantly in real-world use cases on roads and motorways and it is the introduction of new regulatory tests such as the WLTP that have contributed to pushing manufacturers to clean up their act.

A sample of vehicle results from the AIR Index

Source: AIR Index, MarketLine

A potentially worrying trend is that premium vehicles are performing better

It is perhaps too early to judge the progress of individual manufacturers in their endeavour to clean up their diesel models because ultimately doing so takes time and requires a significant amount of investment and the AIR index is yet to test many models.

However, other independent testing done in Germany by the German Automobile Club does show that premium manufacturers such as BMW and Mercedes are smashing their targets, while more mainstream high-volume manufacturers such as Renault and Dacia are missing theirs. The Mercedes Model C 220D, for instance, actually emitted zero NOx during road testing, whilst the Renault Clio 1.5DCI from 2017 emitted 621mg/km.

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