ULEZ: A step in the right direction but will still let ‘dirty diesels’ into the capital, says AIR

Press release from AIR on the launch of London’s Ultra Low Emissions Zone (ULEZ)

  • Allow Independent Road-testing (AlR), the publishers of the AIR Index, the independent, standardised on-road emissions rating system, welcomes London’s Ultra Low Emissions Zone (ULEZ)
  • However, AIR’s own testing has found that the Euro emissions standards bear little resemblance to what comes out of a car’s tailpipe in urban driving
  • There is huge variation in Euro 6 diesels, and although the latest are very clean there are still millions of dirty diesels on European roads that can emit in excess of Euro standards for urban NOX, yet still gain free access to ULEZ
  • The AIR Index is calling on policy makers in London and across Europe to make clean air zones more effective by tackling the issue of dirty Euro 6s – using ratings such as the AIR Index– to bring air quality into legal compliance as soon as possible
  • To learn more about the AIR Index and see a rating for your vehicle go to

8 April 2019 Today’s launch of the Ultra Low Emission Zone (ULEZ) in London is an impressive and welcome step on the road to cleaning up urban air quality but will not stop ‘dirty diesels’ from entering the capital despite controlling access based on emissions.

London’s policy has ambitious scope, is complemented by action on other vehicles such as buses and trucks, and avoids outright bans by using a charging mechanism to create an efficient mechanism to abate nitrogen oxide (NOx) emissions.

Allow Independent Road-testing (AIR), the publishers of the AIR Index, the world’s only fully independent, standardised on-road emissions rating system, which gives cars a rating based on their actual urban NOx emissions, has already warned that using Euro emissions standards are a poor proxy for urban emissions, as many vehicles emit way in excess of accepted limits.    

Under the ULEZ scheme, penalty-free access to the centre of London will only be granted to petrol cars with a minimum Euro 4 standard while diesels must comply with the Euro 6 standard. These apparently different limits are in fact logical as they both equate to 80 mg/km of NOx.  But tests conducted for AIR and rated in the AIR Index show that many Euro 6 diesels will legitimately still be producing many times the officially published NOx limit, with free access to ULEZ.

The Euro standards are the officially accepted levels of emissions recorded during tests conducted mainly by car makers themselves, on their own products and until recently entirely in laboratory conditions. However, emissions recorded during on-road driving in urban conditions, including stop-start in traffic, bear little resemblance to the emissions recorded during laboratory tests where vehicles can be optimised to achieve specific results.

When a 2017 Renault Clio 1.5 litre dCi diesel was tested and rated in the AIR Index, it emerged that the supermini emitted 20 times more NOx in urban driving than a 2018 Land Rover Discovery 3.0 litre TD6 diesel, yet both fall under the category of ‘Euro 6’. What’s more, some Euro 6 diesels produce more urban NOx than earlier, cleaner Euro 5 vehicles. The results of variations between Euro 6 vehicles was presented at the launch of the AIR Index in February 2019.

Why is there such variation? Following Dieselgate, Euro 6 was tightened up, but rather than issue a new Euro 7 standard, Euro 6 has continued to be used but with suffixes. It now (confusingly) straddles a wide spread of permitted emissions,” explained AIR Index Co-Founder, Nick Molden.

“Whilst the latest phase of the Euro 6 standard – in this case 6d which includes on-road testing – does set low levels of urban NOx emissions, millions of cars with a pre-Euro 6d standard have been sold across Europe and some are still on sale today.  All these have unlimited ULEZ access since they fall within the overall Euro 6 stage.

“The fundamental issue we have with ULEZ access being based upon Euro standards alone, is that is not an efficient or fair way to address the problem of urban NOx emissions from vehicles, since over-emitting newer Euro 6 cars will be allowed in, yet older lower-emitting Euro 5 cars will attract penalty fines.”

The AIR Index rates vehicles tested in urban conditions to the same standardised methodology providing comparable NOx emissions levels that more accurately reflect the contribution to urban air quality than existing tests performed in a laboratory.

It has been created to inform and empower car buyers and city policy makers with the real facts about vehicle emissions when making choices about car purchase and usage. A simple A-E colour-coded rating, shows the difference between clean and dirty vehicles based on how much NOx comes out of a car’s tailpipe in urban driving.

“We believe that ULEZ should be based on a better source of data.  Without a better source, the positive benefits will be seen more slowly, and the number of car-owners affected will be greater than necessary. It would immediately be more effective if used in conjunction with the ratings provided through the AIR Index,” commented Operations Director and Co-Founder of the AIR Index, Massimo Fedeli. “This would enable access to only the cleanest vehicles and limit the over-emitting vehicles from adding further to poor urban air quality. Specifically, a C-rated Euro 5 diesel could be let in, but an E-rated Euro 6 should not be.”

At the launch of London’s ULEZ, AIR is calling on policy makers across Europe to look at the most effective way to use actual vehicle emissions, not just laboratory standards, as the basis for policies which will bring cleaner air, more quickly to everyone.

“Even at the most optimistic predictions, the current rate of adoption of zero emission vehicles is not happening quickly enough to help us, our friends and families, colleagues and citizens who need immediate respite from urban air pollution,” continued Massimo Fedeli. “To make rapid progress, we need to make best use of the cleanest internal combustion engine technology available today and deliver a real improvement in air quality immediately. There can be no excuse for failing to use the most effective ways available to us now, to improve urban air quality for everyone.”


Media contacts

Email   PressOfficer@allowAIR.org

Call      +44 (0) 7815 863 968

About the AIR Index

Cars 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 cars, 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 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.
  • Dr Martin Williams, Professor of Air Quality Research, Kings College London.

AIR’s full mission statement can be found here.

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.

1 see https://www.eea.europa.eu/airs/2018/environment-and-health/outdoor-air-quality-urban-areas  

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.

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 www.allowair.org 


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