WEBINAR Replay- With Nick Molden, Emissions Analytics' Founder and CEO

Thank you all who joined the webinar with
Nick Molden, Emissions Analytics' Founder and CEO on 15th October 2018. 

If you missed the webinar please find the replay link below:

We hope you enjoyed the webinar and found it useful. 

If you have any questions from the webinar please e-mail your questions too:

Recap on the webinar: 

Much rides on the new Real Driving Emissions regulation working: the credibility of the auto industry and regulators, as well as consumer confidence in the internal combustion engine.  This webinar seeks to demonstrate real-world emissions performance on the most recently certified passenger cars in Europe, and to examine what that reveals about the automakers approach to emissions reduction and compliance.  

Specifically, the webinar will cover:

  • Real-world NOx and PN emissions on the latest Euro 6d-temp passenger cars from the EQUA Index programme

  • Comparison to pre-RDE vehicles

  • Manufacturers’ approach to emissions reduction

  • Sensitivity of emissions levels to vehicles being driven outside of normal driving

  • Effects under cold start and filter regeneration

  • Compliance risk under normal driving, and potential for elevated emissions outside of RDE boundaries

Running time: 1 hour

Real Driving Emissions is a tough regulation, but also a risky one


Aggressive driving on average increases pollutant emissions by 35% in rural driving and by around five times on the motorway, according to testing of the latest passenger cars by Emissions Analytics on its EQUA Index programme.  Even higher “hotspots” have also been identified, where emissions at high speed can peak at more than ten times typical levels of nitrogen oxides (NOx) – the pollutant gas that was at the centre of the #dieselgate scandal.
The need to identify hotspots is becoming vital with the new Real Driving Emissions (RDE) regulations, which is a much tougher regulation of driving in normal conditions.  The consequence of this will be that a greater proportion of total emissions may be concentrated in a small number of more unusual or extreme events.  Unless those are well understood, the effect of the new regulations may be blunted.
The in-use surveillance requirements set out in the fourth package of RDE are aimed at monitoring vehicle compliance in all normal driving conditions, not just the cycle on which the vehicle was certified.  Broadly, a vehicle should pass any RDE test within its useful life, whenever and whoever conducts the test.  This is both a significant challenge for manufacturers, and brings with it risk as it is impossible a priori to guarantee compliance on all possible RDE tests.
To help quantify this risk, Emissions Analytics is launching a new evaluation programme that will quantify the risk of excessive emissions for each vehicle tested.  Currently, EQUA Index ratings ( are published to allow the performance of different vehicles to be compared on a standard, normal cycle.  This new programme leaves that rating unchanged, but puts the vehicle through an extended test designed to measure performance in more extreme and unusual driving conditions.  The variance between that, the standard EQUA Index and the regulated level will yield a rating for the risk of exceeding the regulated level.
The main factors considered are: 

  • Higher speeds
  • Higher and lower rates of acceleration
  • Cold start emissions
  • Emissions under regeneration of the diesel particulate filter.

Considering eight diesel cars certified to the new RDE standard (Euro 6d-temp), the effect of driving at speeds up to 160 kph can be shown in the chart below.


In all cases the NOx emissions on the standard cycle – with maximum speeds up to 110 kph – are within the regulated limit of 80 mg/km plus 2.1 times conformity factor, even though certification does not apply this to the motorway section separately.  In fact, many of the vehicles are comfortably below this limit.  Allowing the maximum speed to rise to 160 kph shows significant proportionate increases on all but one vehicle, with the average percentage increase across all eight vehicles being 552%.  All but two of the vehicles remain below the limit despite the increases; however, the worst two vehicles emitted around 650 mg/km.
For reference, under the RDE regulation, the vehicle’s velocity can be driven between 145 and 160 kph for up to 3% of the total motorway driving time.  The risk of compliance therefore comes from a vehicle that has a significant emissions uplift at 160 kph and is relatively close to the limit at more moderate speeds. 
Under cold start, vehicles 7 and 8 also showed an average increase in emissions of 160% compared to an average of 110% across the other vehicles. 
Putting this data together with performance in other parts of the test cycle, it is possible to derive ratings of the risk of excessive emissions on RDE and on RDE-like cycles but with more relaxed boundaries, as shown in the table below.


It is important to note that a red rating does not necessarily imply non-compliance but, rather, it identifies elevated risk of non-compliance using results from the Emissions Analytics’ test, which runs a cycle similar to RDE but that is not strictly compliant.

Considering Euro 6 diesels, whether RDE or prior, the effect of cold start is that NOx emissions are 2.8 times higher on average during the cold start phase compared to the whole warm start cycle.  During regeneration of the diesel particulate filter NOx emissions are on average 3.3 times higher than in mixed driving with no regeneration.  Therefore, the frequency and geographical location of these events can be critical to the overall real-world vehicle emissions.
These results are important for cities, manufacturers and regulators.  For cities, it is vital to know that the latest vehicles do not have emissions hotspots that could undermine their air quality targets.  For manufacturers, facing third-party RDE testing to check compliance, it is important to quantify the risk of high emissions being found in unusual driving conditions, where every scenario cannot practically be tested.  For regulators, it is important that RDE is seen to function well in order to draw a line under the failed regulation of the past.

Emissions Analytics will continue to test a wide range of the latest vehicles to publish comparable ratings between vehicles, but now with the added quantification of the risk of elevated emissions around the boundaries of normal driving.

Discrepancies between best and worst diesel cars reaches record high

The first diesel vehicle that met the regulated Euro 6 limit for nitrogen oxides (NOx) on our real-world EQUA Index ( test using a Portable Emissions Measurement System (PEMS) was in May 2013.  Of the vehicles we tested in that year, the cleanest 10% of diesels emitted 265 mg/km and the dirtiest 10% emitted 1777 mg/km – a ratio of 7 to 1.  In 2017, the cleanest 10% achieved an impressive 32 mg/km, but the dirtiest 10% were 1020 mg/km, a ratio of 32 to 1.

On average, progress has certainly been made, with average diesel NOx emissions having fallen from 812 mg/km to 364 mg/km from Euro 5 to Euro 6, or a 55% reduction, driven by the prospect of the new Real Driving Emissions (RDE) regulations together with the aftermath of dieselgate.  The very worst vehicles have now disappeared from the new car market.  It is also true that in around 10 years’ time, the majority of diesels on the road are likely to be of the cleaner variety, through natural turnover of the fleet.

We have now tested six of the latest RDE-compliant diesel vehicles, also known as 'Euro 6d-temp'.  Their average NOx emissions were 48 mg/km, 40% below the regulated limit itself, and 71% below the effective limit once the Conformity Factor of 2.1 is taken into account.  (As ever, it should be noted that while the EQUA Index test is broadly similar to an RDE test, it is not strictly compliant.)  However, it should be noted that there are many cleaner diesels even before RDE, with 30 prior models achieving real-world emissions of 80 mg/km or less.

While this sounds like good news, the elongated transition to RDE, and growing spread from the best to the worst, are creating a growing policy and consumer choice problem in the meantime.  A vehicle in the highest-emitting decile today will likely be a significant contributor to urban NO2 pollution.  Yet, the cleanest diesels are getting close to the average NOx emissions from new gasoline vehicles, which is 36 mg/km.  Without the contemporary data to show this, policy makers would be forgiven for simply banning all diesels from urban locations.

The lowest NOx emission recorded so far this year is the 2017 model year Mercedes CLS, with selective catalytic reduction after-treatment and type-approved for 6d-temp, which recorded 15 mg of NOx per km.


New Real Driving Emissions regulation increases pressure on annual inspection and maintenance testing system

The European Union Roadworthiness Directive came into force on 20 May 2018 and will play a role in enforcing type approval emissions limits, subtly but powerfully changing its role and previous focus on safety, to the benefit of air quality.
In the new inspection and maintenance test, known for example as the MOT test in the UK, a ‘major’ defect and automatic fail arises from any visible smoke being emitted by any car equipped with a diesel particulate filter (DPF), meaning in practice the majority of vehicles since late 2009 (Euro 5 onwards).
The definition of ‘visible smoke’ has only tightened up for vehicles registered after 1 January 2014, meaning late Euro 5 and all Euro 6. Permitted smoke for these cars has more than halved from 1.5m-1 to 0.7m-1. This measurement is familiar to any MOT tester and denotes opacity, where 0.0 m-1 is totally clear and 10.00 m-1 is totally black. In practice, less than 0.7m-1 is judged to be invisible and more than 0.7m-1 will be visible.
For vehicles from 1 July 2008 to 31 December 2013, the standard is 1.5m-1, while the smoke standard for older cars remains unchanged, at 2.5m-1 (non-turbo) 3.0m-1 (turbo).
Air quality campaigners have been quick to note the perversity of a tougher test that only applies to newer cars. However, it has long been politically unfeasible to apply new standards to old cars, which would see the wholesale removal of vehicles that met their type approval at the time of their manufacture.
The revised smoke test for vehicles since 2014 is likely to catch out cars where the DPF is absent or defective. Particulate emissions rise by orders of magnitude when the DPF is missing or blocked. In the UK, 1800 cars have been caught without a DPF since 2014, but the true figure is believed to be much higher because it is notoriously difficult for testers to identify DPF removal in the small amount of time taken to perform the MOT.

In an exercise Emissions Analytics conducted in 2017 with BBC 5 live Investigates, a car with its DPF removed still passed its MOT at three (out of three) different garages. Mechanics failed to spot the filter had been taken out on each occasion, and the car was not failed for opacity.

To quantify the difference between having a DPF and not having a DPF, Emissions Analytics technicians tested a 9.0 litre commercial diesel engine before and after the installation of a DPF retrofit. The particle number (PN) and particle mass (PM) afterwards were close to zero, so the reduction was over 99%. Therefore, tampering would increase the emissions by orders of magnitude.


As this problem of DPF removal detection has not been eliminated, it is believed that the tougher smoke test will most likely identify missing filters, although we think a greater degree of tester training and adherence to test processes is also required. 
A weakness of the new test is that is does virtually nothing to enforce emissions limits for nitrogen dioxide (NOx). Emissions control equipment is only subject to a visual check for its presence, including the oxygen sensor, NOx sensor and exhaust gas recirculation valve.
Should any of these items be ‘missing, obviously modified or obviously defective’, the car fails the test. However, the new (UK) MOT Manual skimps over this area by suggesting in section (Exhaust emission control equipment for diesel engines), telling testers, “You only need to check components that are visible and identifiable, such as diesel oxidation catalysts, diesel particulate filters, exhaust gas recirculation valves and selective catalytic reduction valves.” We suspect that in numerous cases this requirement will be neglected owing to the continued difficulty of determining the presence of some of these items, or because of commercial pressures to complete tests quickly.
Almost all Euro 5 diesel cars had no NOx after-treatment, just exhaust gas recirculation (EGR), while their Euro 6 successors typically received the addition of either a Lean NOx Trap (LNT) or a Selective Catalytic Reduction (SCR) system.  Therefore, as a rough equivalence, a Euro 6 car with failed after-treatment may emit at a level more akin to an equivalent Euro 5 vehicle.
Emissions Analytics has tested numerous Euro 5 and 6 cars on its on-road EQUA Index ( route. For example, a Euro 5 VW Golf 1.6 litre diesel emitted 0.557 g/km of NOx, while its LNT-equipped Euro 6 successor emitted 0.161 g/km, a reduction of 71%.
Then take the larger Mercedes C-Class 2.1 litre diesel. In Euro 5 guise it emitted 1.226 g/km of NOx; and with SCR fitted to the Euro 6 version the same engine emitted 0.396 g/km, a reduction of 68%.
From these results it is clear that to disable these treatments (with an “emulator” or similar) or where they have malfunctioned, NOx could increase by a factor of over 3.
However, the dilemma in setting an in-service NOx standard is that the performance of vehicles when brand new varies from around 20 mg/km to over 1500 mg/km – the issue uncovered as a result of the dieselgate scandal.  A vehicle normally producing 20 mg/km that is malfunctioning might produce 800 mg/km, whereas a different model may produce 800 mg/km when in a fully functioning condition.  Therefore, a real-world reference number is required to judge the in-service performance.  The EQUA Index rating, which is a standardised test on the vehicle when new, could act as this reference value to increase the accuracy of identifying malfunctioning vehicles.
One unmistakable outcome is that what was once mainly a test for roadworthiness has now become a more complex enforcement of type approval emissions, at the very moment when those limits are tightening up within WLTP/RDE.
The inspection and maintenance system has in this sense risen in importance as a tool for policing emissions, because non-compliant vehicles will display vastly increased emissions, by orders of magnitude.  However, the failure to test properly for NOx misses one of the major problems that Europe faces, in the wake of its dieselisation, while the ultrafine particles produced by downsized, direct injection petrol engines are also missed. It feels as though the new test is distinctly lacking in these crucial areas, leaving much more work to be done.

Rethinking Scrappage For Addressing Vehicle Emissions

Scrappage schemes are controversial. In a 2011 academic paper* reviewing 26 studies assessing the outcomes of 18 scrappage schemes implemented around the world in 2008-11, the authors concluded that the emission effects of the schemes were ‘modest and occur within the short term.’ They also concluded that the cost-effectiveness of such schemes ‘is often quite poor.’
The reality of the 2008-9 scrappage schemes, however, was that governments in Europe, the US and Japan were tackling a liquidity gap by stimulating consumption and bolstering an ailing car industry. The mooted environmental benefits of accelerated fleet renewal were talked up by politicians but were not the main objective. This helps to explain why the efficiency of the schemes in mitigating Greenhouse Gas (GHG) emissions - CO2 dominating discussion at the time - was found to be poor value for the taxpayer and of marginal consequence to overall path reductions towards a low carbon economy.
Since 2008-9, the policy climate has changed significantly, with air quality emerging as a major concern. Several national governments have been sued by environmental groups for illegal levels of NOx in cities, and what was once a transport policy issue has become a matter of public health. With diesel bans looming in city centres, plus the advent of clean air zones, it’s no stunt to reimagine scrappage according to an emission-reduction imperative.
Data availability upon which to base an intelligent scrappage scheme has also improved.  Since 2011 Emissions Analytics has compiled the world’s largest database (the EQUA Index) of standardised real-world emissions tests, of over 2000 cars. The EQUA Index test measures not just CO2 emissions but nitrogen dioxide (NO2) and carbon monoxide (CO), as well as fuel efficiency.
Reimagining scrappage in light of air quality first requires accepting that the now discredited New European Driving Cycle (NEDC) test regime has produced counterintuitive outcomes, to the point where some of the newest cars are by no means the cleanest. This means that a poorly designed scrappage scheme could produce a worse outcome, measured in air quality, than doing nothing at all.
The EQUA Index results show that:

  • Dirtiest Euro 6 diesels are 6-7 times worse than cleanest Euro 5
  • Dirtiest Euro 6 diesels are up to 3 times worse than cleanest Euro 3/4
  • Some 20-year-old cars are cleaner than some brand new cars

How one weights GHG emissions against NOx emissions is a matter of policy debate and public acceptance, but a plausible objective would be Pareto optimality, or the idea that addressing air quality should not be at the expense of GHG such as CO2. While research points towards life cycle or ‘well to wheel’ analysis of CO2 emissions, this is difficult to measure and for the sake of a near-term scrappage scheme probably lies in the future.
Beyond the well-observed conflict between efficiency, where diesel scores well compared to gasoline, and the point-of-use emissions, where gasoline is consistently cleaner with respect to certain emissions such as nitrogen dioxide, the point to make is that it is possible to target and scrap dirty cars without increasing CO2.
The EQUA Index test recently revealed that 11 Euro 6 diesel cars from four manufacturers merited an A+ rating, equivalent to 0.06 g/km NOx in the EQUA Index test, which compares with a limit 180% higher (0.168 g/km NOx) for the new RDE requirement that will prevail until January 2021. Such cars can be said to be genuinely clean by today’s standards, but were greatly outnumbered by highly polluting diesel models, 38 of which scored F, G or H, meaning that they exceeded the Euro 6 limit in respect of NOx by 6-15 times. By comparison, 105 gasoline and hybrid Euro 6 cars achieved the A+ rating, and only one gasoline model fell into the D category, the rest being C or higher.


In the graph above, the arrow labelled ‘Bad Trade’ travels from a Euro 4, 1.9-litre diesel Skoda Octavia, model year 2009, that scored E in the EQUA Index test, towards a Euro 6, 1.6 litre diesel Nissan Qashqai, model year 2016, that scored H in the EQUA Index test. The Skoda is cleaner than the Nissan in real-world testing, yet a scrappage scheme designed around vehicle age alone could result in the cleaner Skoda being scrapped for purchase of an equivalent, dirtier Nissan Qashqai. This would result in tailpipe emissions higher by a factor of more than five and therefore worse air quality. It would be a waste of tax payer money.
Conversely the ‘Good Trade’ arrow highlights that dirty older (and conceivably newer) vehicles could be scrapped for genuinely cleaner new vehicles. Currently, 87% of Euro 6 diesel cars are over the Euro 6 limit, as are all Euro 5 cars. If all these cars were replaced by Euro 6 cars actually performing to the Euro 6 diesel standard in real-world conditions, the net tailpipe emissions improvement measured in NOx would be around 88% from the Euro 5/6 fleet.  If real-world performance were only brought down to the Euro 5 diesel standard, the reduction in emissions would be 74%.  Even if performance were reduced to just Euro 3 levels, there would still be a 38% reduction.
Put another way, as most Euro 5 and 6 diesels emit over the limit, a large number of vehicles need to be “fixed” to address the air quality problem.  This inherently makes any scrappage scheme highly costly.  Therefore, a more stratified approach may be optimal, as shown in the chart above.  Emerging passenger car retrofit technology may deliver a 25% or more reduction in NOx; those vehicles with moderately high emissions could be tackled in that way.  A scrappage scheme could then be targeted on the dirtiest diesels (perhaps worse than the Euro 3 level in real-world).

A further potential ‘Bad Trade’ may be switching from a diesel car to a non-hybridised gasoline car.  The same vehicles viewed through the lens of CO2 emissions show that on average, gasoline vehicles are, like-for-like, a ratings class worse than diesels for absolute CO2 emissions. They also exhibit a greater disparity between NEDC measurements and actual emissions. For example, the 2017 Audi Q2 diesel, achieves A+ for air quality and C2 for CO2. The same power output gasoline equivalent model from the same year also achieves A+ for air quality, but a lower D4 for CO2. C means 150-175g/km CO2; D means 175-200 g/km, but the numbers 2 and 4 respectively show that the gasoline engine model is at greater variance from the officially claimed figures. This example highlights an element of the trade-off involved if tackling air quality results in a more gasoline-dominant fleet.
In summary, the right scrappage and retrofit schemes could incentivise consumers towards vehicles that are genuinely clean and genuinely efficient, taking into account not just NOx emissions, but also CO2 and particulates. This would contrast with the UK’s 2009 scheme that merely required customers to scrap their old car for any new vehicle. A stratified and discriminating scheme would require a more focussed replacement, resulting in better results both for air quality and climate change.
* Bert Van Wee, Gerard De Jong & Hans Nijland (2011) ‘Accelerating Car Scrappage: A Review of Research into the Environmental Impacts’, Transport Reviews, 31:5, 549-569, DOI: 10.1080/01441647.2011.564331

Cutting pollution and improving public health

Pollution is a major contributor to chronic human sickness, not just environmental damage, according to the 2017 annual report of England’s Chief Medical Officer, Professor Dame Sally Davies, released on 2 March 2018:  The report made 22 policy recommendations, many of which related to monitoring and ameliorating pollutant emissions.
Emissions Analytics is pleased to have had its EQUA Index real-world emissions rating system ( cited in the report.  With the failure of the previous EU vehicles emissions regulatory regime, having led to around 40 million high-NOx-emitting diesels on European roads, the need to base policy on real-world emissions has grown, as illustrated in the chart below. Each point represents a vehicle we have tested, and the horizontal line shows the regulated limits. 


It is clear that at each Euro stage the cleanest vehicles have been getting cleaner, while the dirtiest vehicles have not.  Therefore, any system of discriminating between vehicles based only on Euro stage will be highly inefficient as it will involve permitting some vehicles with high real-world emissions.  The particularly problematic Euro stages are 5 and 6, within which there are significant spreads from the best to the worst.  For example, the dirtiest Euro 6 diesels are six to seven times higher emitting than the cleanest Euro 5.  More striking still, the dirtiest Euro 6 diesels are around three times worse than the cleanest Euro 3/4 vehicles, last of which were type-approved in 2009.
In summary, using the EQUA Indices would allow governments and cities to target only those vehicles which are high emitting in practice, minimising the private and public cost.  Any system based only on official Euro standards would be costlier and less efficient.  Estimates of the benefit suggest that 54% of Euro 6 diesels would have to be restricted from urban areas to achieve an 87% reduction in nitrogen oxide emissions.
Many of the Chief Medical Officer’s recommendations revolve around the need for evidence-based action.  This has been dramatically lacking in emissions policy, due to the difficult choices it would present.
One recommendation specifically calls on local government and public health professionals to implement concrete solutions.  The Mayor of London’s publishing of the EQUA Aq ratings for NOx on its official website ( is an example of proven action that could be applied in any city across Europe.  Another recommendation talks about providing toolkits to assist local authorities.  With the challenges of Clean Air Zones, the priority is to link up the existing empirical evidence with policy action on the ground.
An example of this is when regulating against particulate number emissions: current certification of particle number (PN) emissions is down to 23 nanometres in size. However, ambient pollution laws still focus on PM2.5, or 2500 nanometres in size.  The concern about ultrafine particles has been growing, as the penetration of direct injection gasoline engines has increased. 
Latest test data from Emissions Analytics also suggests than certain diesels are now lower in CO2, carbon monoxide (CO) and PN emissions that many gasoline cars, and equivalent levels of NOx.  This should be carefully borne in mind as policy increasingly slants away from all diesels.
The Chief Medical Officer’s report also recommends a standardised approach to pollution surveillance and road charging to give vehicle drivers a simple and consistent system.  While the new Real Driving Emissions (RDE) regulation is robust, it is not simple and consistent, which will limit its effect in rebuilding consumer trust.  In particular, previously launched cars will not be systematically retested on RDE and therefore there will be no comparability with new cars.
Finally, the current lack of trust in car manufacturers is not to the benefit of them, consumers, the market or society.  A further recommendation calls for transparency on the part of industry as to the polluting effect of their activities.  Emissions Analytics believes this is a necessary first step to rebuilding that trust.
Emissions Analytics hopes the simple, independent and free-access nature of the EQUA Index is a good place to start to reassert evidence-based policy and the health of the automotive industry.

Electric vehicles now rated by EQUA Index – Tesla 3 result.

Electric vehicles have no tailpipe emissions – obviously.  They do have indirect emissions from upstream manufacturing, and in-use emissions from tyre and brake wear, but it is range and efficiency which are of direct practical importance to owners.
As range anxiety diminishes with larger batteries, the relative efficiency of EVs will become more important in choosing the best vehicle.  More challenging, for car buyers, is weighing the advantages and disadvantages of EVs against traditional powertrains, as they decide whether to switch.  As a result, Emissions Analytics has extended its EQUA Index programme to test these new powertrains in a comparable way, with our partners Motor Trend (
Recently, we put the Tesla 3 through the standard EQUA Real Mpg fuel economy test in the California, which is the same test we put internal combustion engine vehicles and hybrids through. The Tesla performed well, achieving efficiency of 3.1 miles per kWh. While there is no ideal way to convert this to a miles-per-gallon equivalent, if the kWh are converted to gallons based on relative energy content, this makes 103.7 (US) mpg, 124.5 (Imperial) mpg or 2.27 litres per 100 km.


This was a good performance, but not best-in-class. The 2017 Chevrolet Bolt we tested achieved 122.2 US mpg and the 2017 Hyundai Ioniq EV reached an impressive 151.8 mpg.
This is significant because it shows that the electric vehicle market is not just dominated by one player, but there are now a number of rival vehicles, with varying performance – information the consumer should have when making a purchase decision.  Emissions Analytics’ EQUA Real Mpg data for the US market can be found at, and the equivalent European data at

At the same time as these developments, behind the scenes, Emissions Analytics has initiated a process to formalise its methods and evolve it to be relevant for testing the latest vehicles, including European diesels under Real Driving Emissions and EVs. In November, the inaugural workshop of this "CEN" process was held in Brussels. CEN, or Comité Européen de Normalisation, is a framework for standardisation of products and techniques across the European Union.  After a period of open scrutiny and discussion, the testing methodology could become an official voluntary standard, for any organisation to use.
Emissions Analytics is undertaking this as part of its commitment to the recently-launched not-for-profit global alliance called “Allow Independent Road-testing” or AIR ( As part of this, we want to open up our methodology to third parties to conduct consistent tests, in order to grow the global database of comparable results. 


AIR is a separate entity from Emissions Analytics and structured as an alliance allowing like-minded organisations to sign up to the principles of independent testing and labelling. Any organisation interested in finding out more about the objectives and opportunities for membership, should contact Massimo Fedeli at
The link between these two recent events is that the ever-growing complexity of car choices needs an accurate, fair, trustworthy standard for measuring efficiency and emissions. Consumer trust must be rebuilt and cities need good tools to meet the air quality goals.

Can driving styles prove the smarter route to better fuel economy and emissions?

The relevance of official fuel economy figures is still a perennial topic across the automotive industry, and one of the hardest to answer directly takes into account the human factor. Some claim that the official figures are in fact perfectly valid, if only the average driver wasn’t so lead-footed. But is there any truth in this train of thought?

Thinking laterally, one way to assess this question is to consider a scenario where the UK parc features a high penetration of connected and autonomous vehicles (CAVs).  By taking the driver out of the loop an autonomous vehicle could deliver a more “responsible” and consistent driving style.  This would in turn consume less fuel and so deliver significant reductions in nitrogen oxide (NOx) and carbon dioxide (CO2) emissions, then perhaps the driving style hypothesis is true.

To look at this very question Emissions Analytics and Imperial College London collaborated on the “Optimised Vehicle Autonomy for Ride and Emissions” feasibility project, supported by the Centre for Connected and Autonomous Vehicles and Innovate UK.

The research methodology started with Emissions Analytics performing on-road PEMS tests of 21 vehicles to its standard EQUA Index protocol across the UK and Germany.  This provided second-by-second driving characteristics and the simultaneous emissions, allowing an emissions map for each car to be created.


These were then integrated with VISSIM traffic simulation software to model the effects of traffic flow and driving behaviour on the emissions. The simulation covered three main factors: vehicle driving strategy, communication between vehicles and infrastructure, and the penetration of CAVs. This included scenarios were a CAV followed a normal vehicle, a non-CAV followed a CAV, and CAV following another CAV.

We also factored in the ability for CAVs to communicate with traffic lights allowing them to approach a junction knowing when they were going to change, and so avoid coming to a complete stop.

In essence, the virtual CAVs were configured to mimic a more cautious and gentle driver with better anticipation of the road ahead and smoother style of driving.  The benefit of the approach was we could model a world of 100% CAV penetration, but also the transition to that point via a mixed fleet of CAVs and non-CAVs.

The headline results are that, with 100% CAV penetration with congested traffic, NOX and CO2 could be reduced by approximately 20%. The preliminary analysis assumes a simplified scenario with only diesel cars, so the results are not yet reflective of the current UK fleet. It is plausible that petrol vehicles would show a similar CO2 reduction, while NOX emissions are typically low NOX whatever. Overall, the results show that smoother traffic flow could have significant benefits in urban areas.

This suggests that optimised driving styles can deliver lower vehicle emissions.  However, according to our EQUA Index (, on average diesel NOx emissions are approximately five times the regulated limit on average (399 mg/km), and CO2 emissions are 40% above official values (based on the New European Driving Cycle).  This means that even if driven more responsibly the average vehicle will only reduce its NOx exceedances to about a factor of four, and the CO2 exceedances to 30%.  While this is an improvement, and underlines the benefits of driver training initiatives, it strongly suggests that the driver is not responsible for the majority of the emissions exceedances observed.

The chart below shows the reduction in NOx, as the penetration of CAVs increases from 0% to 100%. The benefits are seen is a broadly linear way as penetration increases, although the majority of NOx emissions still come from non-CAV vehicles even when CAV penetration passes 60%.


In summary, even if the driver and all associated “bad” driving habits are eliminated, the current fleet of vehicles will still well exceed official CO2 values, and diesel vehicles will exceed the NOX limits.  Modifying driver behaviour can offer a valuable mitigation to these exceedances, but real-world emissions are still primarily determined by vehicle selection.

Very cleanest cars revealed: new A+ rating from the EQUA Index

Emissions Analytics’ EQUA Index ( has been revealing the cleanest and most efficient cars since it launched in 2016.  Since then, technology and vehicle performance have improved to a point that a new class of even cleaner vehicles can now be revealed.

On 17 October, the Mayor of London, in collaboration with Emissions Analytics, launched an online Cleaner Vehicle Checker ( with a new EQUA Aq A+ rating for those vehicles with the very lowest emissions of nitrogen oxides (NOx).  This identifies 105 Euro 6 petrols meeting this more stretching standard and 11 diesel engines from four manufacturers.

To achieve the A+ rating a vehicle must emit no more than 0.060 grams per kilometre of NOx across the real, on-road EQUA Index test, made up of equal proportions of urban, rural and motorway driving. This is 25% more stringent than the A rating of no more than 0.080 grams per kilometre.  It is also significantly tougher than emissions required under the new, official Real Driving Emissions (RDE) regulation, under which 0.168 g/km (180% higher) are allowed until 2021.


A recent study, conducted by Imperial College London on behalf of the campaign group Allow Independent Road-testing (AIR,, concluded that RDE and the EQUA Index tests are broadly similar in how demanding they are on the vehicle.

The new A+ rating illustrates dramatically the challenge that diesel engines face, but also shows that they shouldn’t be automatically consigned to the history books. Not that many years ago, governments encouraged car buyers to opt for diesel cars in order to reduce carbon dioxide (CO2) emissions.  However, the NOx emissions were much higher (often five times higher, and more than the petrol cars they replaced), and even the CO2 emissions were higher than the official figures suggested (often 40% or more adrift).

With the progress in standard “full” hybrid technology – ignoring for a moment plug-in hybrids – the newest models now delivers Mpg comparable with diesels. This in-turn means that on average CO2 as well as NOx emissions are lower too – the best of both worlds.

Does this spell the end for diesel passenger cars?  Maybe. The loss of confidence in the automotive industry combined with the political narrative, nationally and locally, may be hard to correct. Consider the new Volkswagen Passat 1.6 litre diesel, with an EQUA Aq rating of A+, an EQUA CO2 rating of B and EQUA Mpg of 52.6 mpg. Compared to the latest Hyundai Ioniq petrol hybrid with EQUA Aq of A+, EQUA CO2 of A and EQUA Mpg of 58.1 mpg.  The diesel has impressively low NOx emissions, but the hybrid is beating it on fuel economy and CO2 emissions.


So, the battle between diesels and hybrids is on.  Can diesels shrug off the legacy of those Euro 6 diesels still on the market with EQUA Aq H ratings (12 or more times the regulatory NOx limit)?  Does the current performance of hybrids obviate the need for alternative powertrains to meet urban air quality goals?  Whatever happens, the EQUA Index will be tracking through its independent, real-world test programme.

The EQUA Index data can be accessed for free at  There are four ratings for each vehicle: EQUA Aq rating for NOx; EQUA CO2 for carbon dioxide; EQUA CO for carbon monoxide; and EQUA Mpg for fuel economy.  In publishing the EQUA Aq A+ ratings, the boundaries for categories B to H have not been changed.

Why cold starts could freeze air pollution improvements

The latest analysis of the EQUA Index data shows that the average daily distance driven in passenger cars is not sufficient for a vehicle’s pollution control system to warm up and become fully functional. The resultant high levels of cold start NOx emissions, from both gasoline and diesel engines, could provide an additional challenge for urban air quality initiatives such as the proposed Clean Air Zones in the UK.

According to the Department for Transport[1] more than half of car driver trips nationally are under 5 miles. In Inner London, the average journey distance by car per-person-per-day is just 1.5 miles[2]. For the majority of vehicles tested by Emissions Analytics, it can take more than five minutes for after-treatment systems to reach operating temperature.

The table below shows the uplift in NOx for cold starts tested at 1 minute and 5 minutes from key-on, compared to when fully warm, across the combined EQUA Index cycle.

Screen Shot 2018-03-26 at 12.38.32.png

Gasoline has lower NOx in absolute terms but proportionally has much higher NOx in the first minute, but which then falls more rapidly than for diesel cars. This is typically as the three-way catalyst reaches effective operating temperature.

More generally, the thermal management of exhaust systems for engines where the exhaust frequently cools, such as with stop-start technology or hybridisation, is of growing importance in limiting NOx emissions.

By looking at the average NOx emissions of 5% of the data with lowest instantaneous exhaust temperatures from each Euro 5 and 6 passenger car test (excluding data points where the engine is off), and comparing it to the average NOx emissions when the engine is warm, it shows a very similar picture to the cold start data.

Screen Shot 2018-03-26 at 12.38.45.png

Gasoline engines suffer proportionally much more from cooler exhausts although produce less NOx in absolute terms, whereas the diesel engines have a 29% uplift in NOx when the exhaust temperature is lower. In terms of total emissions, the average uplift is 0.160g/km for diesels and 0.067g/km for gasoline vehicles.

The potential introduction of Clean Air Zones in UK cities is a cornerstone of the government’s strategy to reduce air pollution. However, driver behaviour in cities (short trips, the use of stop-start technology and/or choice of hybrid vehicles), when combined with exhaust after-treatment technologies which are sensitive to exhaust temperature, means that other measures will be necessary if NOx emissions are to be reduced.

Encouragingly, the EU has acknowledged the importance of cold start emissions by including their measurement in the new Real Driving Emissions regulations that start in September 2017. However, there is a danger that the effects are under-measured compared to real-world journeys of short length.



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.

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:


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:

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?

The EQUA Mpg gap increases further in 2016

This year’s round up of EQUA fuel economy data shows a five percentage point increase in the gap between official and real-world mpg, reaching 29% in 2016.

Official mpg figures averaged 60.7mpg in the year, the highest we have seen since we started recording in 2011. This is an increase of 9% on 2015’s figures, which stood at 55.7mpg; however, real-world mpg reached just 42.3mpg. On a like-for-like basis, this represents a 3% increase on 2015.


Air conditioning

With air conditioning now widely available in cars, in 2016 Emissions Analytics updated all its mpg results to include the effect of air conditioning on fuel economy. Results are now expressed to reflect manually adjusted air conditioning (not automatic climate control) switched on at 50% of maximum throughout the test. This increases fuel consumption typically by 4%.

Incorporating the use of air conditioning, the gap between official mpg figures and real-world EQUA Index Mpg has risen to 29% on average, with the largest gaps well exceeding 40%. This increases to 75% below the official figures for hybrid vehicles that have not had their battery charged and are running purely on the ICE.

Can regulatory change reduce the gap?

From 1 September this year the World harmonised Light duty vehicle Test Procedure (WLTP) will be introduced to certify the carbon dioxide and fuel economy of cars. Work started on this around 2008 and was originally intended to be a worldwide certification standard. However, with the passing of significant time and the withdrawal of North America from the process, it has become less relevant.

It will still be an improvement on the existing type approval process, which incorporates the New European Driving Cycle (NEDC), largely due to the removal or restriction of loopholes in the procedure.  However, the test cycle itself is not much more representative of real-world driving, as it remains in the laboratory with no changes in elevation and still modest acceleration rates. Our prediction, also consistent with modelling from the International Council on Clean Transportation, is that the current mpg gap of 29% and the CO2 gap between official and real-world of around 40% will approximately halve. So, a significant gap will still remain.

Crucially, it has yet to be agreed when and in what way the WLTP results will be made available to consumers. In the meantime the EQUA Index is available for anyone wishing to find out the on-road fuel economy of both Euro 5 and Euro 6 vehicles.

Can hybrid electric vehicles beat diesels on mpg?

Hybrids have always had a miles-per-gallon advantage in urban driving but new EQUA Index data shows that they are gaining on diesels in motoway or highway driving and, if current trends persist, hybrid electric vehicles (excluding plug-in hybrid electric vehicles) are set to take the lead in 2017.


The dotted trend lines in the above graph, representing motorway mpg for diesel vehicles and gasoline hybrids tested by Emissions Analytics, are converging. While the downturn in diesel mpg may be due to a change in manufacturers’ focus from fuel economy to NOx emissions, what is more striking is the improvement in gasoline hybrid performance on the motorway as a result of technological advances.

The step change in technology is even more noticeable when European EQUA data is compared to North American EQUA results. The graph below shows gasoline hybrid performance in the US is particularly impressive on our combined cycles. With this level of fuel economy it seems unlikely that diesel vehicles will ever make a significant impact on market share in the US. With the mpg penalty of some NOx aftertreatment systems, perhaps it was to gain a fuel advantage over hybrids that Volkswagen resorted to using a defeat device when bringing their diesel models to the US market.


Another noticeable effect of the different product mix in the US is the level of carbon monoxide emissions. Both regular gasoline cars and gasoline hybrids have much lower CO emissions than their European equivalents, with regular gasolines 30% lower and gasoline hybrids 64% lower. This is despite the fact that the US have a less strict limit, at 2.1g/km, than the EU’s, 1.0g/km limit.

When we last wrote about hybrid vehicles back in October 2014, we concluded they were delivering “good but not best-in-class fuel economy, but [were] typically the cleanest, and if you are a light-footed, congested town driver, they are ideal.” Two years on hybrids, particularly in the US, have really upped their game. They are still a cleaner drive than a diesel and may soon offer better fuel economy wherever you drive them but heavy-footed drivers should still exercise caution.

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?