emissions analytics

Thermal windows: the next big scandal or an innocent technicality?

Recent months have seen a growing a body of evidence, from different sources, that NOx emissions from cars are higher when the ambient temperature is lower.  This month, Emissions Analytics mined its real-world database to assess the evidence.

The accusation is that NOx reduction devices, including exhaust-gas recirculation, are programmed for reduced operation below the 20°C of the official test.  The effect would be higher NOx emissions, with  the motivation supposedly to deliver better real-world fuel economy.

Some manufacturers argue that this is, in fact, to protect the engine from damage at lower temperatures, and that doing this is perfectly legal. However, with average temperatures in the UK around 9°C across the year, this has a potentially significant impact on air quality and governments’ attempts to achieve air quality targets.

To quantify the issue, we segmented NOx data from our on-road PEMS tests into groups above and below 18°C, and found the following differences in the average Conformity Factor (ratio of real-world NOx to official limit).

Conformity Factors of Euro 5 & 6 vehicles above and below 18°C


While the result for the Euro 5 vehicles was statistically significant, this was not the case for Euro 6 due to a small number of very high emitters.  As our sample size increases, we will be better able to assess whether there is a pattern for Euro 6 cars.

Looking in more detail at the Euro 5 vehicles, the data suggests that there are seven manufacturers with clearly higher emissions below 18°C, which is shown in the chart below.

Conformity Factors for Euro 5 vehicles by manufacturer


The intention of this newsletter is not to name names, but to indicate that it is not one manufacturer but several that may be utilising the thermal window loophole.  If the hypothesis is correct, it could mean that many millions of vehicles on the road today in UK and the colder parts of Europe are putting out higher emissions than expected.  Further, as Euro 5s, these vehicles are not that old and therefore will be on the road for many years to come.

Emissions Analytics to power Clean Vehicle Checker for London and Paris

  • London and Paris to use on-road emissions data to improve air quality
  • Emissions Analytics’ data to help inform consumer decisions in both cities
  • EQUA Index launched today in France

 In a drive to improve urban air quality, the cities of London and Paris will launch an on-road emissions scoring tool for residents, using Emissions Analytics’ data. The partnership was announced at C40 Air’volution in Paris today as Mayor of London, Sadiq Khan, and Paris Mayor, Anne Hidalgo, set out their joint plan to tackle poor air quality in both cities. Emissions Analytics has also launched its emissions database, the EQUA Index, in France today.

The Greater London Authority’s (GLA) online Clean Vehicle Checker will allow Londoners to identify the cleanest and worst-polluting new vehicles on sale. Launching in Autumn this year, the free-to-access tool will provide Londoners with on-road emissions data for nearly all new cars and vans. The Mayor of Paris, Anne Hidalgo, has committed to offering a similar scoring scheme.

The move to offer car buyers information on real-world emissions data comes as authorities try to address the consequences of the official emission testing system, which has historically underestimated true ‘on road’ emissions. Emissions Analytics data shows that some new cars produce more than 12 times the legal NOx limit in the real world. While the introduction of official Real Driving Emissions (RDE) tests will help to address this, it is not set to come into full force until 2021, and vehicle manufacturers will still be allowed to exceed limits by up to 50%.

Nick Molden, CEO and founder of Emissions Analytics, said: “Both the Mayors of London and Paris have identified that vehicle emissions in the real world are a major contributor to the current air quality issue. This validates the work of Emissions Analytics, which has been recording on-road vehicle emissions for six years. We are delighted that both cities will be using our data to help inform consumer decisions.”

Emissions Analytics’ EQUA Index, which provides free-to-access data on vehicles’ fuel consumption and NOx, CO2 and CO emissions, has also been launched today in France. The EQUA Index will allow Europe’s third-largest new car market to better understand the emissions that their vehicles produce in real-world driving conditions for free, by going to fr.equaindex.com.

Independently financed and implemented, the EQUA Index is designed to help end the confusion that many consumers face when trying to understand the complex subject of fuel economy and tailpipe emissions, with ratings openly published and freely available to all.

Developed by Emissions Analytics, the EQUA Index is totally independent of car manufactures, trade associations and government. The EQUA Index is a scientific undertaking, providing highly accurate information, obtained though standardised and repeatable testing conducted on real roads.

Notes to Editors

Nick Molden, CEO and founder of Emissions Analytics, is available for interview and comment on the issues relating to real-world fuel economy data and vehicle emissions.

Notes to Editors

About Emissions Analytics

Emissions Analytics is a specialist in real-world, on-road vehicle emissions measurement and analysis, covering the European Union and the United States.

Its capabilities cover the measurement of regulated pollutants, including CO, CO2, NO, NO2, NOx, total hydrocarbons and particulate matter, using officially certified Portable Emissions Measurement Systems (PEMS).

Operating since 2011, it has carried out PEMS tests on more than 1400 model variants of passenger car in addition to testing heavy goods vehicles, tractors, taxis, vans and buses. It is the unrivalled expert in the field of on-road emissions monitoring.

Its bespoke services include benchmark tests, product evaluation and real-world running costs and it offers subscription access to its database of test results, as well as confidential testing services for product development and evaluation.

As experts in vehicle emissions and fuel consumption, Emissions Analytics supports a range of commercial and publicly funded organisations. It is currently in partnership with Imperial College, London, studying urban emissions for transport planning and policy.

Emissions Analytics is willing to provide journalists with sample data for specific vehicles upon request.

 About the EQUA Index

The EQUA Index is designed to evaluate the performance of individual passenger cars across the European Union in terms of fuel economy and tailpipe emissions under real-world driving conditions.  The scheme will assess cars using objective performance criteria, recognising the best performers in emission levels through the ratings awarded.

The on-going programme will be separate from, and independent of, vehicle manufacturers’ certification tests. The results will be publicly available, with the aim of influencing policy development and implementation, allowing consumers to make informed purchase decisions and demonstrating the improvements that vehicle manufacturers are making in fuel efficiency.

A technical reference document on the methodology is available on request.

The EQUA Index is owned, funded and operated by Emissions Analytics, which retains all rights associated with the results and ratings.

For more information, please contact:

Alex Michaelides (Torque): 020 7952 1078, amichaelides@torqueagencygroup.com

Matt Sanger (Torque): 020 7950 1079,

New testing cycle brings CO2 taxation uncertainty

Industy experts have raised the prospect of fleets paying higher emissions-based tax bills following the introduction of  the Worldwide Harmonized Light Vehicles Test Procedure (WLTP), which will replace the existing New European Driving Cycle (NEDC) test in September 2017 and is expected to inflate official vehicle CO2 figures due to its stricter rules.   


Business Car, 30 November 2016

Are diesels done for?

As the government loses a second high court ruling brought by ClientEarth, many are now sounding the death knell for diesel cars. Not so fast, says Emissions Analytics, diesels can be clean and govenments are highly unlikely to give up the greenhouse gas advantage of diesel in the short- or medium-term.
Since the introduction of Euro 6 in September 2014, manufacturers have been forced to improve their after-treatment systems to meet the stricter legislated limits for NOx. Exhaust Gas Recirculation, Lean NOx Traps, and Selective Catalytic Reduction technologies have been employed as part of a complex strategy to reduce tailpipe emissions. There have been variable successes, with some achieving the regulated limits even in real-world driving and the worst more than 20 times the legal limit. Overall, average NOx emissions from Euro 6 diesels are down 55% compared to Euro 5s.

Nonetheless, there is still the fact that many new cars do not meet the legislated limits in real-world operation. Our data shows NOx emissions are on average 4.3 times over the limit for Euro 6 cars and, after a period of improvement, this Conformity Factor is rising. This is the heart of the issue, as to whether diesels are the major and unavoidable cause of poor air quality in towns and cities.

Consequently, there have been many suggestions made to combat the problem of dirty diesels. These range from the London Mayor’s T-charge, to a diesel scrappage scheme, to a total ban on diesel vehicles in certain zones. However, Emissions Analytics’ data shows that modern diesels in their own right can be clean.

Since the launch of the EQUA Air Quality Index six months ago, twelve cars have how achieved an A-rating including the latest Volkswagen Tiguan, meaning it has met the 0.08g/km limit in real-world driving.


This proves that diesels can be clean and the reason most are not is down to a failure of regulation and enforcement and not the technical impossibility.

There is also the issue of CO2 emissions to be considered. Despite Donald Trump tweeting that climate change was, “created by and for the Chinese in order to make U.S. manufacturing non-competitive,” the British government has an empirical view on global warming and stands by its commitment to cutting its carbon footprint. Would ministers give away the 16% CO2 advantage – according to Emissions Analytics’ testing – diesel has over gasoline for the same distance driven in real-world operation, until there is a viable alternative.

In the future electric and hybrid vehicles may deliver the CO2 advantage required, as well as greatly reducing, or eliminating, NOx and other harmful emissions, at which point diesel powered engines for passenger cars may come to the end of the road. However, with a share of the market of less than 2%, there is still a way to go for these vehicles. Until then, Emissions Analytics’ data strongly suggests the policy focus should be on sorting the clean from the dirty diesels and incentivising manufacturers to bring forward clean technology.

The latest EQUA Aq Index results are available online

Emissions Analytics launches EQUA Carbon Monoxide Index

Emissions Analytics is pleased to announce the launch of the EQUA CO Index. The second in the EQUA Index series, EQUA CO looks at whether carbon monoxide regulations are being achieved in real-world operation.

Potentially fatal for humans as well as damaging to the environment, carbon monoxide is generally considered a problem primarily confined to gasoline vehicles. Regulations distinguish between the fuel types, with diesels having a more stringent but, due to their technology, easier to achieve limit of 0.5g/km. Gasoline vehicles have to meet a more generous 1.0g/km limit which is typically achieved using a three-way catalyst. Therefore, the regulations are not technology neutral and allow gasoline vehicles to emit twice that of diesels and still be compliant.

In the same way that Emissions Analytics rates emissions of NOx from diesels, gasolines and hybrids with a single scale on the EQUA Aq Index, the EQUA CO Index awards a universal rating regardless of fuel type. Thus despite the regulations setting different boundaries, the EQUA CO Index allows comparisons between vehicles. The A++ to H ratings are set as follows:


Using these classes, a diesel car awarded an A to A++ meets the regulated level even in real-world driving, whereas a gasoline vehicle with a C to A++ meets the regulated levels for this fuel.

Of the 734 vehicles currently on the EQUA CO Index, 96% emit the regulated amount of CO or less. However, there are some interesting exceptions. Several Mercedes C-Class diesels are over 0.5g/km, out of a small number over the limit. Additionally, 8% of gasoline vehicles, that is 24 models tested by Emissions Analytics, do not meet the regulated limit, with one outlier being more than six times over. If the regulations were to change and gasolines had to achieve the same, stricter standard as diesels, the number of cars failing to reach this standard would increase to 20%. Of the hybrid vehicles tested, all achieve the regulated limit apart from the Mitsubishi Outlander which scored a D-rating when not running on its electric engine.

The vehicles tested by Emissions Analytics are all  run on our standard real-world cycle. The tests are conducted by a small pool of highly trained technicians and the vehicle and testing equipment is carefully prepared to make sure it is fully warmed up and in the manufacturers’ default settings.


The data shows that illegal levels of carbon monoxide are not as prevalent in real-world driving as excess NOx from diesels. However, given the toxicity of CO, this is a situation that needs to be monitored. This could become particularly relevant if there is a market shift away from diesel towards gasoline as a result of dieselgate and other emerging regulations and taxes. Emissions Analytics will continue to keep a watchful eye on on-road vehicle performance, checking it against official certification and publishing the results online on the Carbon Monoxide page at the EQUA Index site.

Subscriptions are available to the Emissions Analytics database. Contact us for details.

New EQUA Index reveals true pollutant emissions for car buyers

With Mitsubishi Motors the latest manufacturer to admit to impropriety in its testing procedures, the need for impartial real-world data has never been greater. Today Emissions Analytics is launching the new EQUA Index rating scheme to help bring transparency in the first instance to the issue of air quality.

The EQUA Air Quality Index is based on the level of emissions of nitrogen oxides (NOx) in grams per kilometre emitted during our real-world tests. The Index aligns the boundaries between ratings values as much as possible with recognisable points. See below:

apr-16-table (1).jpg

The EQUA Air Quality Index is intended to complement the forthcoming regulations for new vehicle certification, by monitoring vehicle performance when driven normally on roads; in effect keeping a watchful eye on the effectiveness of the new regulations.The problems with the existing test system, the NEDC, which have been the cause of so many of the issues covered by the media recently, are already being addressed by regulators in Europe. From 2017 the World Harmonised Light Duty Test Protocol (WLTP) will change the way CO2 is measured and Real Driving Emissions will address problems with NOx measurement.


The other great benefit of the EQUA Air Quality Index is to help car buyers. Designed to be clear and concise, the simple A to H rating allows manufacturers and retailers to show how different models compare in the showroom, whether diesel, petrol or hybrid. It is also ideal for car reviewers and publishers to include as new cars are reviewed. And because the scheme is independently financed and researched, consumers, companies and the wider automotive industry can have confidence in the impartiality of the data.

The EQUA Air Quality Index has been developed by Emissions Analytics in conjunction with a group of experts to guide, review the test and rating methodology, monitor the regulatory context, and provide input into the wider development of the index. The group includes:

  • Professor Helen ApSimon – Air Pollution Studies, Imperial College London, UK
  • Dr Adam Boies – Department of Engineering, The University of Cambridge, UK
  • John German – Senior Fellow, The International Council on Clean Transportation, USA
  • Dr Marc Stettler – Centre for Transport Studies, Imperial College London, UK
  • Professor Martin Williams – Air Quality Scientist, King’s College London, UK

There are almost 450 vehicles on the EQUA Air Quality Index now, so why not have a look?