The AIR Alliance welcomes the Irish Government’s ground-breaking NOx-based car tax emissions plans

Pioneering approach must use trusted, independent data to be fair and effective, which only the AIR Index provides

  • The Irish Government has taken global leadership with plans to replace the existing diesel surcharge with a NOx-based approach
  • NOx is the biggest contributor to poor urban air quality and the AIR Alliance applauds any move to focus on emissions in this way
  • ‘Polluter pays’ taxation must be based on reliable, trusted and independent data, which the AIR Index provides
  • The AIR Index shows a huge variation between real world NOx emissions of Euro 6 compliant cars and stated data from manufacturers  
  • The AIR Index shows the actual nitrogen oxides (NOx) urban emissions for each vehicle using an A-E colour-coded rating, endorsed by global air quality and emissions experts  
  • Companies and drivers are advised to check the AIR Index to make the most informed decision before buying a new or used car
  • More information available at the AIR Index website

17 October 2019: The AIR Alliance, publishers of the AIR Index welcomes the Irish Government’s new plans to introduce a tax based on a vehicle’s NOx emissions, replacing the current one per cent diesel surcharge – but cautions that such a system can only be truly effective if it uses NOx data based on the actual emissions produced during on-road driving.

Set to be applied to new car purchases and used imports from 1 January 2020, under the terms of the ground-breaking new NOx tax, the first 60mg/km of NOx emissions from new cars will be charged at a rate of €5 per mg.

Above 60mg/km of NOx, the charge increases to €15 per mg, and above 81mg/km it jumps to €25 per mg. The NOx charge will be capped at a maximum of €4,850 for diesel vehicles and €600 for other vehicles. The Irish government quoted average NOx emissions from new cars at 43mg/km which  means that for the majority of new diesel models, the charge will just about directly replace the existing one per cent Vehicle Registration Tax (VRT) on diesel engine cars.

However, as the AIR Index revealed from  tests earlier this year, the homologated data, reflected in the certificate of conformity, does not reflect on-road emissions in urban driving . A significant number of Euro 6 vehicles still emit significantly more NOx on the road than in the laboratory test used for their type approval and there is huge overall variation between cars despite them all complying with Euro 6 emissions standards.

Created to inform and empower consumers, owner-drivers, fleet operators and policy makers with the real facts about emissions when making choices about vehicle purchase and usage, the AIR Index is a vital and independent tool in helping to clean up urban air quality.

Using scientifically robust, on-road vehicle testing according to the latest CWA 17379 methodology giving each vehicle a simple A-E colour-coded rating, showing the difference between clean and dirty vehicles, the AIR Index is the world’s first international, independent and standardised rating system to reveal accurately how much pollution a vehicle produces when it is driven in towns and cities.

Inspiration for the AIR Index has been NCAP, the independent vehicle-safety rating system developed in the US in the 1970s that became the industry standard in the EU and around the world. The programme held car makers accountable for their safety performance, resulting in a voluntary adoption of technologies that led to safer vehicles.

Massimo Fedeli, Co-founder and Operations Director, AIR said: “We applaud the Irish Government for making the bold step to link a financial car tax charge to the milligrams of NOx emitted in light of public health and environmental concerns. Reducing NOx in urban areas is a core focus for the AIR Alliance, so this is a very positive move.

“However, as results of on-road NOx emissions tests conducted for the AIR Index reveal, there is a shocking variation in actual emissions compared with stated official results. We would be delighted to work with the Irish Government to make this tax as effective as possible, using our database of real-world emissions results, to distinguish the clean from the dirty cars enabling informed choices within this polluter-pays policy.”

Nick Molden, Co-founder of AIR said: “This is a ground-breaking and positive step towards cleaning up air quality in our cities. However, it needs the most accurate information on real-world NOx emissions, which only the AIR Index provides.

“The choice of which NOx rating is used will be critical to the success or failure of the policy.  Anything based purely on laboratory figures will significantly underestimate actual emissions, and therefore the tax would not reflect the level of emissions produced during on-road urban driving. 

“Cleaning up air quality requires the application of a tax like this not just to the latest vehicles, which are much cleaner, but also to the older Euro 6 and earlier vehicles, which are the actual primary and significant source of nitrogen oxide emissions – which is why this new tax must be based on an independent, reliable and trusted source of real-world data for new and used cars – the AIR Index.

“Our real-world emissions results are easy to understand and easy for the public to find. What is more they identify the heroes and villains right now, helping us to tax those cars which are truly dirty, allowing policy makers to clean up the air immediately.”


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About the AIR Index

Cars and vans rated for the AIR Index are tested according to the CWA 17379 standardised methodology which ensures that the results are independent, comparable and can be used as the basis for a legal framework for vehicle policies.

The testing is carried out on at least two vehicles, sourced independently from vehicle manufacturers with portable emissions testing units (PEMS) recording actual on-road driving in towns and cities.  For a result to be considered acceptable for rating in the AIR Index there must be at least five, 10 km trips completed during three separate journeys on at least two matching vehicles in line with the CEN standard.  

The results of the tests provide the basis to rate the vehicle according to the A-E, colour-coded scale.

The AIR Index website includes more than 200 results of the first tests conducted with ratings A-E, but also provides a facility to check other vehicles on the road to see if they would be allowed access (or not) to the 14 German cities which have set a NOx limit of 270 mg/km under the Federal Emissions Control Act.

Other cities across Europe are considering a similar threshold to control access and allow only the cleanest cars to enter. Car and van buyers should consider carefully the implication for a vehicle’s residual value, and their own mobility requirements, if it is unable to enter a town or city where emissions are controlled.

About AIR

AIR (Allow Independent Road-testing) is an independent alliance of public and private organisations, which promotes the voluntary uptake of independent on-road emissions testing.

The alliance’s key objective is to contribute to delivering a cost-effective and timely reduction in harmful vehicle emissions in urban areas, while ensuring the lowest CO2 emissions from the global vehicle fleet.

AIR seeks to empower citizens, industry and public authorities to take informed decisions on their mobility practices and policies by promoting full transparency on vehicle emission levels.

Scientific Advisory Committee

The development of the AIR Index has been led by the world’s leading academics in the fields of emissions and air quality and they make up AIR’s Scientific Advisory Committee (SAC).

  • Professor Helen ApSimon, Professor of Air Pollution Studies, Imperial College London.
  • Dr Adam Boies, Reader in the Energy Division, Department of Engineering, University of Cambridge.
  • Dan Carder, Director for Alternative Fuels, Engines and Emissions, West Virginia University.
  • Dr Claire Holman, Chair, Institute of Air Quality Management.
  • Dr Guido Lanzani, Head of Air Quality Unit, Regional Environmental Agency, Lombardy Region.
  • Dr Norbert Ligterink, Senior Research Scientist, TNO.
  • Martin Lutz, Head of Sector Air Quality Management, Berlin Senate Department for Environment, Transport and Climate Protection.
  • Dr Xavier Querol, Institute of Environmental Assessment and Water Research, Spanish Council for Scientific Research.
  • Dr Marc Stettler, Lecturer in Transport and the Environment, Centre for Transport Studies, Imperial College London
  • Professor Martin Williams, Professor of Air Quality Research, Kings College London.

More information about the AIR Alliance’s mission.

Notes on European Air Quality

The European Environment Agency provides independent information on the environment for those involved in developing, adopting, implementing and evaluating environmental policy and the general public. In its latest report, published in April 2018, updated in November 2018, the European Environment Agency stated that for particles and nitrogen dioxide, because of the widespread exceedance levels in urban areas, it is unlikely that the air quality standards for these pollutants will be met by 2020 across the EU.

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Background to the AIR Index testing process

Emissions Analytics (EA), founded by Nick Molden (Co-founder of AIR), was a pioneer in methodologies to test on-road emissions using Portable Emissions Systems (PEMS) equipment. The experience and insight gained from more than 2,000 tests conducted by EA informed the development of the CWA 17379 protocol on which the AIR Index rating is based.Paragraph

Emissions Analytics has licensed the use of its data including the EQUA Index within the AIR Index database, enabling insight for car buyers and policy makers as to whether vehicles are allowed access (or not) to enter cities which have set a NOx limit of 270 mg/km. Further information about Allow Independent Road-testing (AIR) can be found at

Would you donate £10 to support the work of the AIR Alliance?

We provide practical solutions, including the AIR Index vehicle ratings, to ensure that independent, scientifically robust data are available to inform discussions and policy decisions which can help reduce the impact of harmful vehicle emissions. We are guided by a committee of the world's leading emissions and air quality experts who give their time and expertise to support our common goal of improving air quality and tackling the climate crisis. The AIR Index ratings and our expertise are used by public authorities and organisations across Europe to inform policy decisions. The AIR Alliance is a not-for-profit organisation and we fund our own testing and scientific programmes to provide AIR Index ratings free of charge. Please would you consider making a donation to support our work?

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