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Vehicle Market Surveillance Unit: results of the 2019 programme

Published 4 January 2023

This publication is licensed under the terms of the Open Government Licence v3.0 except where otherwise stated. To view this licence, visit nationalarchives.gov.uk/doc/open-government-licence/version/3 or write to the Information Policy Team, The National Archives, Kew, London TW9 4DU, or email: [email protected].

Where we have identified any third party copyright information you will need to obtain permission from the copyright holders concerned.

This publication is available at https://www.gov.uk/government/publications/vehicle-market-surveillance-unit-programme-results-2019/vehicle-market-surveillance-unit-results-of-the-2019-programme

The Driver and Vehicle Standards Agency (DVSA) has a market surveillance unit, which inspects vehicles, trailers and equipment to make sure they meet safety and environmental standards.

This report sets out the findings of vehicle and component testing during 2019. You can also download the unprocessed raw data for all of the tests carried out.

There's an annex that explains some of the emissions reduction technologies mentioned in the report.

DVSA aims to check a representative selection of the most popular vehicle types used on UK roads. In 2019, we carried out tests on:

The vehicles were chosen based on their UK sales, with other vehicles added in to make sure a wide range of manufacturers were included.

DVSA sourced vehicles from hire fleets or bus operators.

The vehicles were not provided by manufacturers and they could not prepare or modify the vehicles before they were tested.

DVSA tested the vehicles to make sure they conformed to European emission standards:

The types of tests DVSA carried out depended on:

For cars and light vans, DVSA carried out the following tests:

Before carrying out the tests the vehicles:

The majority of cars and light vans tested in 2019 were type approved using the New European Driving Cycle (NEDC).

Vehicles approved under NEDC do not need to meet the requirements of the Worldwide Harmonised Light Vehicle Test Procedure (WLTP) or Real Driving Emissions (RDE) test.

DVSA still carried out on-road tests and track tests on NEDC approved vehicles in order to understand how they perform under real world conditions.

The vehicle is given a standard pre-conditioning test relevant to its approval. It's then left in a temperature controlled room so that the whole vehicle including engine oil and coolant is ‘soaked’ to a temperature between 20°C and 30°C (as specified in type approval regulations). Following that the test starts with emissions measured from engine start.

This is a legislative test with limits that a vehicle's emissions must not exceed.

This test is the same test as the cold test, but starts with a fully warmed up engine.

This is not a legislative test and is carried out to gather additional information on the vehicle's performance.

The test consists of 4 repeated urban driving cycles and one extra-urban driving cycle. These drive cycles cover 11 kilometres (km) and take 20 minutes to complete. The test has an average speed of 34km per hour with the maximum being 120km per hour.

WLTP replaced the NEDC test procedure for measuring the official fuel consumption, carbon dioxide (CO2) and pollutant emissions of new cars in September 2017. It became mandatory for all new cars powered by an internal combustion engine by September 2018.

WLTP tests are designed to give a more accurate indication of how much fuel the vehicle will use, and the pollutants emitted during driving.

The WLTP test takes 30 minutes to complete and covers just over 23km with an average speed of 45km per hour and maximum speed of 131 km per hour.

This test is carried out on public roads using Portable Emissions Measuring System (PEMS) equipment. This test measures pollutants while the vehicle is being driven.

This test involves driving the vehicle for around 1 and a half to 2 hours over a test route on public roads. The route included urban, rural and motorway driving and tests were carried out during the day in normal traffic conditions.

If temperatures drop below 3°C during this test, this is considered ‘extended’ conditions and the emissions results for the test are divided by a factor of 1.6. For transparency reasons in this report ‘raw’ RDE results have not been post-processed and have not had additional factors such as the extended conditions factor applied.

For NEDC approved vehicles and some WLTP approved vehicles sold before September 2019, this is not a legislative test. For these vehicles, it is an additional test that DVSA carried out to understand how they perform under real world conditions.

This test is carried out on a closed track using Portable Emissions Measuring System (PEMS) equipment. It's designed to check that the vehicle's emissions did not increase disproportionately compared to the laboratory tests.

The test follows the driving pattern used in WLTP tests. It is carried out by providing the driver with a screen showing a trace of the speed versus time that they needed to maintain for each section.

For HGVs and PSVs, DVSA carried out an on-road test using Portable Emissions Measuring System (PEMS) equipment.

Before carrying out the tests the vehicles:

This test involves driving the vehicle for around 2 and a half hours over a test route on public roads. The route included urban, rural and motorway driving and tests were carried out during the day in normal traffic conditions.

The emissions measured in this test are normalised to the laboratory engine test using carbon dioxide as an assessment of the amount of ‘work done’. We use this to calculate mass emissions per unit of energy (measured in kilowatt-hours, kWh).

The result is then compared to the laboratory limit to determine whether it is within the conformity factor specified in legislation.

The conformity factor is the maximum permitted ratio of the normalised test result in g/kWh compared to the emissions limit specified for type approval engine testing.

For HGVs and PSVs, the nitrogen oxides (NOx), hydrocarbons (HC) and carbon monoxide (CO) levels all have a conformity factor of 1.5. This is because:

Tests were carried out at a selection of commercial emission test laboratories across the UK.

DVSA did not use laboratories that are owned by vehicle manufacturers.

Where vehicles were found to have performed poorly, manufacturers were given the opportunity to explain the test results and describe the emission control strategies they used.

A summary of these discussions is included in the test conclusions in the results section. They provide insight into why a vehicle may achieve the legal emissions limit when tested on the official test cycle, but may emit significantly higher emissions in other situations.

In this section:

You can download the unprocessed raw data showing the results of each test that was conducted on these vehicles.

Download ‘Car (diesel) data, 2019’ (ZIP, 328MB)

Make: Audi

Model: Q2 S Line

Engine and fuel type: 1598cc Tdi S-A Diesel

Transmission: Automatic 7 speed

Emission standard: Euro 6b

Test reference: 30119

Tested: April 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The Audi Q2 was compliant with all required tailpipe pollutant emission limits under the NEDC cold legislative test.

A number of non-regulatory tests were also conducted to understand if the emissions behaviour of the vehicle changed significantly outside of the legislative test, which might be an indication of prohibited emission strategies.

From the results of both legislative and non-legislative testing, we do not have reason to believe that the Audi Q2 tested was non-compliant with its legal emissions performance requirements.

These tests were carried out before the Court of Justice of the EU judgement in case C-693/18 and subsequent related cases. The findings in this report are based on the legislation in place at the time of the investigation.

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Make: Fiat

Model: 500x Lounge Multijet

Engine and fuel type: 1598cc 88kw Diesel

Transmission: Manual 6 speed

Emission standard: Euro 6b

Test reference: 30245

Tested: July 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The Fiat 500X was subject to three regulatory NEDC cold laboratory tests during the course of testing. Emissions of nitrogen oxides (NOx) during the regulatory tests were found to be variable and in one case exceeding legislative limits for this vehicle type. Higher than expected carbon dioxide (CO2) figures compared to those declared at type approval were also measured during these legislative tests.

A number of non-regulatory tests were also conducted to understand if the emissions behaviour of the vehicle changed significantly outside of the regulatory test, which might be an indication of prohibited emission strategies. Emissions of NOx were found to be significantly higher during the NEDC hot test compared to the NEDC cold test that is used for legislative testing. High NOx levels were also measured during both the RDE on-road test and the WLTC test carried out on a test track, in excess of recommended guidance thresholds of 400 mg/km.

The variable NOx emissions measured during regulatory testing and high levels of emissions within non-regulatory testing were discussed further with the manufacturer.

Fiat explained that they considered the NOx levels in the NEDC cold and NEDC hot tests to be a result of inadequate preconditioning of the vehicle prior to the start of testing. They highlighted that this could result in the NOx storage catalyst (NSC) used within the vehicle's exhaust being partially saturated with NOx at the start of testing, resulting in lower efficiencies of trapping NOx emitted from the engine.

Whilst we do not agree with Fiat's conclusion that the preconditioning cycle applied to the vehicle was inadequate, based on the results of the 3 legislative tests we do not have reason to believe that the Fiat 500X is non-compliant with NOx limits during the NEDC cold test. We were also satisfied that Fiat had provided feasible reasons for measured CO2 figures being slightly higher than declared values.

As a result of further discussions with Fiat on the high real-world NOx emissions of this vehicle, two areas of concern relating to the emission strategy used within the vehicle were identified. These strategies related to the reduced effectiveness of NOx emissions control by the NSC and exhaust gas recirculation (EGR) during extended periods of driving. Further testing and analysis of the vehicle's software was conducted to better understand the strategies being used.

We concluded that the emissions strategy relating to the control of NSC operation was non-compliant and requested for this to be rectified by Fiat. Fiat made us aware of an approved software update that was available for improving the control of NSC operation and removing the strategy considered non-compliant.

This software update was applied to the vehicle and retesting was conducted by us to assess the improvement in emissions performance over an extended steady-state test cycle and over the legislative laboratory test.

The updated software resulted in a significant improvement in NOx emissions over extended testing (around 33% improvement), without compromise to CO2 or other criteria emissions, and analysis of the updated software showed that the non-compliant strategy was no longer present.

We requested that Fiat implemented the software update in the UK on the affected Fiat 500X vehicles via a non-safety recall campaign to ensure maximum uptake of this improvement to the real-world vehicle emissions. This was implemented by Fiat within the UK as DVSA reference number NCA/2021/010 in August 2021. All owners were contacted to request they arrange to have the software update applied to their vehicles.

We continue to have concerns over the emissions strategy relating to EGR operation. Findings from testing relating to EGR operation have been shared with the granting type approval authority and discussions remain underway with Fiat to understand the justification for this strategy.

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Make: Ford

Model: Fiesta Titanium TDCI (2018MY)

Engine and fuel type: 1499cc TDCi Diesel

Transmission: Manual 6 speed

Emission standard: Euro 6b

Test reference: 29903

Tested: February 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The Ford Fiesta was compliant with all required tailpipe pollutant emission limits under the NEDC cold legislative test.

The NEDC lab tests resulted in carbon dioxide (CO2) emissions above declared figures, which warranted further discussion with the manufacturer.

The vehicle is fitted with stop-start. However, this was not active during the test. It has been assessed by us and Ford that with stop-start active and alternator load balance strategy enabled, a CO2 test result within around 15% of the declared CO2 emissions could be achieved.

Ford also commented that the battery on the vehicle was not conditioned properly, resulting in an increase in demand on the alternator. They reported this could have an impact on CO2 by increasing it as much as 15g/km.

Taking this into account, as well as stop-start being disabled, the CO2 result for NEDC cold test could broadly fall in line with the type approved values.

From the results of both legislative and non-legislative testing, we do not have reason to believe that the Ford Fiesta tested was non-compliant with its legal emissions performance requirements.

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Make: Ford

Model: Kuga (2018MY)

Engine and fuel type: 1997cc TDCi Diesel

Transmission: Manual 6 speed FWD

Emission standard: Euro 6b

Test reference: 29475

Tested: February 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The Ford Kuga initially failed but following specific preconditioning this vehicle was found to be compliant with all required tailpipe pollutant emission limits under the NEDC cold legislative test.

Initial NEDC lab tests resulted in nitrogen oxides (NOx) emissions above legislative limits and carbon dioxide (CO2) emissions above declared figures, which warranted further discussion with the manufacturer.

Our initial laboratory cold test results showed the vehicle to be non-compliant when tested for NOx. We ran the laboratory cold tests 3 times and the vehicle did not meet the legislative limit of 80mg/km on any test. On the third cold test, the carbon monoxide (CO) level also exceeded the 500mg/km legislative limit.

We found all tests had high CO2 compared to type approval declared figures of 122g/km. However, stop-start was not active during the laboratory tests, and it is expected that with stop-start active and alternator load balance strategy enabled, a CO2 test result of within up to 10% of the declared number could have been achieved.

We found no clear evidence of diesel particulate filter (DPF) regeneration occurring on any of the laboratory tests (and hence contributing to the elevated NOx emission). However, we observed that the lean NOx trap (LNT) had multiple, strong deNOx events occurring, typically on or around the accelerations to the 100km and 120km per hour cruise speed.

This level of deNOx activity, in combination with the poor catalyst carbon monoxide (CO) conversion efficiency, led us to believe the LNT was "saturated" and the running of NEDC tests with the regulated pre-conditioning cycles was insufficient to completely "condition the LNT". As a result, a DPF regeneration cycle was conducted to condition the LNT ahead of retesting in the laboratory.

NEDC cold testing was repeated post the DPF regeneration pre-conditioning cycle. While the NOx emission result was significantly improved from the initial tests, the result of 106.4mg/km was still higher than the legislated limit of 80mg/km.

RDE and WLTC track tests were also completed but it should be noted that they were undertaken prior to the manual DPF regeneration. RDE testing showed moderately high NOx emission compared to the commission guidance.

Similarly, WLTC track testing showed moderately high NOx emission compared to commission guidance. CO emission levels were high, the main contributor being LNT deNOx events. For both RDE and WLTC track testing, we found no clear indication of a DPF regeneration event occurring.

When we met with Ford, the hypothesis Ford provided was the vehicle was not successfully executing a LNT purge (deNOx) during the laboratory precondition cycles and hence the LNT was "full" at the start of NEDC cold test leading to high NOx emission. Specifically, Ford said they expected and needed successful LNT purge events on the 70 to 100km per hour and 100 to 120km per hour accelerations with positive torque. Due to the driver tipping out (negative torque) on the acceleration, the LNT purge was not completed successfully.

On the request of Ford, the vehicle was retested under laboratory cold and hot conditions (cold test 5 and hot test 2). The results of the retest showed the vehicle to be compliant with NOx results of 66 mg/km vs the 80mg legislative limit, much lower than the original tests.

We note that this vehicle demonstrated difficulty in achieving emission and CO2 performance consistent with the manufacturers original type approval but with specific vehicle preparation and configuration, it was possible to achieve NOx results under laboratory conditions that met legislative limits. The limitation of emission performance with the use of LNT technology for NOx control is well documented and understood.

Ford made us aware they have implemented a twin LNT system on some of their EU6d vehicles in lieu of, for example, an active selective catalytic reduction (SCR) system. We will look to include one of these twin LNT vehicles in a future programme.

From the results of both legislative and non-legislative testing, we do not have reason to believe that the Ford Kuga tested was non-compliant with its legal emissions performance requirements.

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Make: Honda

Model: Civic EX i-Dtec (2018MY)

Engine and fuel type: 1597cc N16A1 88kW Diesel

Transmission: Manual 6 Speed

Emission standard: Euro 6d-temp

Test reference: 30108

Tested: March 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The Honda Civic was compliant with all required tailpipe pollutant emission limits under the WLTC cold and RDE legislative tests.

The RDE tests initially resulted in nitrogen oxides (NOx) levels above the conformity factor, which warranted further discussion with the manufacturer.

Honda were invited to explain the results for NOx. Honda commented that low engine speed and high fuel quantity area was used in the rural phase of the test for acceleration. Under these conditions, it is difficult to keep high levels of exhaust gas recirculation (EGR), therefore NOx levels from the engine are high.

In addition, the sulphur loading on the lean NOx trap (LNT) can reduce its effectiveness in NOx control. Consequently, the vehicle was conditioned with a diesel particulate filter (DPF) regeneration to de-sulphurise the LNT and retested, which brought the vehicle into compliance.

Honda stated they have developed a calibration improvement for RDE NOx performance of the Civic Diesel and have installed it on production models from the 19-20 model year. Honda were asked if this calibration would be available for the 18 model year as there was no technical reason to not do so and 7,946 of these have been sold in the UK, which is 51% of the European market share.

Honda responded as the model in question was compliant no retrospective action would be undertaken.

Although results of our testing are not sufficient to conclude non-compliance of this vehicle type against NOx conformity factors, we believe that variability in emissions performance presents a risk of non-compliance that should be carefully considered as part of the manufacturer's ongoing in-service conformity obligations. Therefore, we have written to the granting type approval authority for this vehicle to ensure that these results are considered as part of ongoing discussions of compliance with Honda.

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Make: Land Rover

Model: Discovery SD4 (2018MY)

Engine and fuel type: 1999cc 177kW Diesel

Transmission: Automatic

Emission standard: Euro 6d-Temp

Test reference: 29735

Tested: February 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The Land Rover Discovery was found to be compliant with all required tailpipe pollutant emission limits for the WLTC cold and RDE legislative tests.

This vehicle demonstrated good control over nitrogen oxides (NOx) emissions through the laboratory cold and hot tests and also the RDE test, which is a legislative requirement for this vehicle.

The WLTC track test resulted in NOx emissions above expected figures. This resulted in further discussion with the manufacturer.

The initial WLTC track test showed moderately high NOx emissions, which was unexpected and believed to be caused by an attempted DPF regeneration. This prompted further testing and analysis.

Analysis of the first WLTC track test NOx data showed very high emission almost directly after "cold start" and subsequent improvement in emissions control during the remainder of the test stage.

We then repeated both the RDE and WLTC track tests, following completion of a diesel particulate filter (DPF) regeneration, to check for any changes this would have in emissions performance. Aside from a notable reduction in particle number (PN), RDE results were comparable to the first test. The track WLTC repeat test gave much improved results, with NOx now within acceptable levels.

We asked Land Rover to explain the reason for the high NOx directly after cold start on the first WLTC track test and to confirm if a DPF regeneration event had occurred relative to the high NOx emission.

Land Rover commented that although it was an unusual occurrence, the lean NOx trap (LNT) did appear to be full and then empty during the early stage of the first WLTC track test.

Land Rover noted that stop-start was not active and the vehicle appeared to perform a DPF regeneration almost immediately after start up rather than waiting for a favourable condition.

Land Rover explained the high NOx emissions on the first WLTC track test were a result of a DPF regeneration at the start of the WLTC track test cycle. This, in combination with a full LNT and an selective catalytic reduction (SCR) system, that was at low temperature and unable to convert the release of NOx from the LNT, resulted in the overall NOx emission being high.

From the results of both legislative and non-legislative testing, we do not have reason to believe that the Land Rover Discovery tested was non-compliant with its legal emissions performance requirements.

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Make: Mercedes-Benz

Model: Vito Tourer

Engine and fuel type: 2143cc Diesel

Transmission: Automatic

Emission standard: Euro 6b

Test reference: 29734

Tested: February 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The Mercedes-Benz Vito was compliant with all required tailpipe pollutant emission limits under the NEDC cold legislative test.

The NEDC cold tests resulted in carbon dioxide (CO2) emissions above declared figures. However, this vehicle was fitted with stop-start technology which was not active during the test. We expect that with stop-start active and the alternator load balance strategy enabled, a CO2 test result of within 10% of the declared number could be achieved.

The NEDC hot test showed higher than expected levels of nitrogen oxides (NOx). At 183.8mg/km, the NEDC hot test registered 53% higher levels of NOx than the guideline. The NOx emission in phase 2 of the hot test had approximately a 700% increase compared to the cold test (157.4 mg/km hot vs 21.2mg/km cold).

RDE and WLTC track testing results showed good emission control and NOx levels were within the European Commision guidance of five times the legislative cycle limit (CF=5).

We shared the test data with Mercedes-Benz and invited them to explain the NOx results found in the Lab hot test.

Mercedes-Benz advised us the vehicle used for testing had been subject to a mandatory recall ordered by the German type approval authority (KBA) on 3 Aug 2018. Mercedes-Benz stated they had informed the vehicle's registered keeper by letter to attend a franchised workshop for the update to be completed. Mercedes-Benz's records showed that the subject vehicle tested had not had the recall completed and the engine software update installed.

As the test vehicle is the subject of a mandatory recall for real world emission improvements, we plan to perform tests on a Mercedes-Benz vehicle that has been recalibrated and publish the results in a later report.

From the results of both legislative and non-legislative testing, we do not have reason to believe that the Mercedes Vito tested was non-compliant with its legal emissions performance requirements.

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Make: Nissan

Model: Navara Tekna DCi Auto (2018MY)

Engine and fuel type: 2298cc YS23 140kW Diesel

Transmission: Automatic 7 speed

Emission standard: Euro 6b

Test reference: 29813

Tested: May 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The Nissan Navara initially failed but following specific configuration this vehicle was found to be compliant with all required tailpipe pollutant emission limits under the NEDC cold legislative test.

Initial NEDC lab tests resulted in nitrogen oxides (NOx) above the legislative limit and carbon dioxide (CO2) emissions above declared figures, which warranted further discussion with the manufacturer.

Due to the initial failures, Nissan was contacted to provide an analysis of the results. Their observation was that the NEDC cold laboratory tests were performed incorrectly and not how the vehicle was originally type approved, with the vehicle being tested by us in four-wheel drive mode and not two-wheel drive mode as approved.

Nissan further advised that their internal testing procedure and the procedure used for Conformity of Production (CoP) testing included testing in two-wheel drive mode and the physical removal of the front prop shaft for safety reasons, as agreed with the granting type approval authority. This information was not available to us at the time of initial vehicle testing.

It was agreed the Navara would be retested at an independent test laboratory with support from Nissan, under our supervision. The vehicle completed two further valid NEDCs (cold retest 1 and 2) with the vehicle configured to match its type approval condition, which demonstrated compliance for all criteria emissions.

The vehicle was also subjected to two further hot NEDC tests at the independent test laboratory with an improvement over the original results noted.

During the RDE test it was found that the particle number (PN) was higher than expected. Post-test analysis confirmed a diesel particulate filter (DPF) regeneration event occurred at the end of the test.

From the results of both legislative and non-legislative testing, we do not have reason to believe that the Nissan Navara tested was non-compliant with its legal emissions performance requirements.

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Make: Nissan

Model: Qashqai (2018MY)

Engine and fuel type: 1461cc Diesel

Transmission: Manual

Emission standard: Euro 6d-temp

Test reference: 30017

Tested: March 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The Nissan Qashqai was compliant with all required tailpipe pollutant emission limits under the WLTC cold and RDE legislative tests.

From the results of both legislative and non-legislative testing, we do not have reason to believe that the Nissan Qashqai tested was non-compliant with its legal emissions performance requirements.

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Make: Porsche

Model: Cayenne (2016MY)

Engine and fuel type: 2967cc 193kW Diesel

Transmission: Automatic

Emission standard: Euro 6b

Test reference: 29837

Tested: March 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The Porsche Cayenne initially failed due to an attempted diesel particulate filter (DPF) regeneration during testing, however this vehicle was found to be compliant with all required tailpipe pollutant emission limits under the NEDC cold legislative test.

Initial NEDC lab tests resulted in nitrogen oxides (NOx) and particle number (PN) emission levels above the legislative limits, and carbon dioxide (CO2) emissions above declared figures, which warranted further discussion with the manufacturer.

Through the initial testing we identified the vehicle had completed a DPF regeneration during the second NEDC laboratory test resulting in high NOx result in this test. The high PN result on the third laboratory test was likely to be a function of the DPF regeneration during the second test. To ensure there was no further test disruption, the vehicle was subject to a manual DPF regeneration and then a fourth cold NEDC test performed. During the fourth test the vehicle was found to meet legislative NOx limits but still had higher than expected CO2.  

We asked Porsche to review and comment upon the NOx result achieved for the NEDC cold test post DPF regeneration and its proximity to the legislative limit. Porsche were only asked to comment on the fourth test due to DPF regeneration affecting the first 3.

Porsche's analysis of the results indicated the NEDC tests used different inertia mass and road load coefficients dyno settings than those used for type approval. At type approval, 2 different dyno settings were used, one for emissions and one for fuel consumption. We only used one set of dyno settings during the NEDC tests we performed. Consequently, the fuel consumption and CO2 emissions tests results were based on different (higher) road load settings than those used for the type approval tests. 

This may explain why the fuel consumption and CO2 emissions results of both the NEDC cold and the NEDC hot test were higher than we expected. The difference of approximately 8% between the CO2 results of the NEDC hot and the NEDC cold test is consistent with Porsche's own experiences. 

Porsche stated that the Cayenne V6 TDI EU6 and the Macan V6 TDI EU6 belong to the same In-Service Conformity (ISC) family. Due to its significantly higher volume, Porsche has performed all ISC testing with the help of the Macan V6 TDI EU6.

Although on a different derivative, to give an indication of the spread of NOx results, we asked Porsche to share this ISC data due to test 4 delivering 75.8mg/km and its proximity to the 80mg/km limit. We note from Porsche's data that 2 vehicles sit in the 65 to 75 mg/km area therefore our test is representative of what we would reasonably expect to see from this vehicle.

Overall, this engine showed good control of NOx across all emission tests following the controlled DPF regeneration. We anticipate that an adjustment to the initial test weight (ITW) and dyno settings, in combination with active stop-start and alternator load balance, could reduce the CO2 emissions in the laboratory tests to acceptable levels. 

From the results of both legislative and non-legislative testing, we do not have reason to believe that the Porsche Cayenne tested was non-compliant with its legal emissions performance requirements.

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Make: Range Rover

Model: Velar (2018MY)

Engine and fuel type: 2993cc 221kW Diesel

Transmission: Automatic

Emission standard: Euro 6d-temp

Test reference: 29550

Tested: January 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The Range Rover Velar was compliant with all required tailpipe pollutant emission limits under the WLTC cold and RDE legislative tests.

RDE on-road tests resulted in particle number (PN) emissions above legislative limits. Our analysis showed the vehicle experienced a diesel particulate filter (DPF) regeneration event during the first RDE test, which is likely to have accounted for the increase in PN.

For RDE certified vehicles it is recommended within the relevant regulations to repeat the RDE test if a regeneration event is suspected. On repeating the RDE test, the PN results were much improved and were comfortably within the legal limit.  

From the results of both legislative and non-legislative testing, we do not have reason to believe that the Range Rover Velar tested was non-compliant with its legal emissions performance requirements.

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Make: SEAT

Model: Ateca Xcellence 4 Drive

Engine and fuel type: 1968cc 150 PS Diesel

Transmission: Manual 6 speed

Emission standard: Euro 6b

Test reference: 29811

Tested: February 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The SEAT Ateca was compliant with all required tailpipe pollutant emission limits under the NEDC cold legislative test.

NEDC lab tests resulted in carbon dioxide (CO2) emissions above declared figures, which warranted further discussion with the manufacturer.

SEAT provided data demonstrating this vehicle type had been compliant during their NEDC emission conformity checks. Therefore, SEAT were asked to explain why CO2 was high during our test. SEAT requested more specific vehicle data such as mileages and condition as well as details of the testing processes carried out to allow them to assess the vehicle behaviour in service.

However, even with the additional data, SEAT were still unable to explain the CO2 difference identified by our tests.

From the results of both legislative and non-legislative testing, we do not have reason to believe that the Seat Ateca tested was non-compliant with its legal emissions performance requirements.

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Make: Suzuki

Model: Vitara SZ5 DDIS Allgrip (2018MY)

Engine and fuel type: 1598cc D16AA 88kW Diesel

Transmission: Manual 6 speed

Emission standard: Euro 6b

Test reference: 30097

Tested: March 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The Suzuki Vitara complied with legislative limits for all criteria pollutants during regulatory NEDC cold testing we conducted. However, measured carbon dioxide (CO2) emissions were higher than those declared by the manufacturer at type approval.

Emissions of nitrogen oxides (NOx) were found to be significantly higher during the NEDC hot test compared to the NEDC cold test that is used for legislative testing. High NOx levels were also measured during both the RDE on-road test and the WLTC test carried out on a test track, in excess of recommended guidance thresholds of 400 mg/km.

The measured CO2 levels during regulatory testing and high levels of NOx emissions within non-regulatory testing were discussed further with the manufacturer.

Suzuki discussed that the most likely reason for the higher than expected CO2 emissions during the NEDC cold test was due to the stop-start system being inoperative during testing, potentially due to a low battery voltage at the start of each test. We were able to confirm that this was the case through analysis of the testing and was satisfied that this provided a feasible reason for measured CO2 figures being higher than declared values.

As a result of further discussions with Suzuki on the high real-world NOx emissions of this vehicle during non-regulatory testing, 2 areas of concern relating to the emission strategy used within the vehicle were identified. These strategies related to the reduced effectiveness of NOx emissions control by the NOx storage catalyst (NSC) and exhaust gas recirculation (EGR) during extended periods of driving.

We concluded that the emissions strategy relating to the control of NSC operation was non-compliant. Suzuki made us aware that they were working with their approval authority (the Netherlands Vehicle Authority, RDW) to gain approval for a software update to improve the control of NSC operation and remove the non-compliant emission strategy. We engaged with RDW to share the findings from our testing and understand their process for approval of the updates.

Following approval of the software update, RDW mandated updates on the affected Suzuki vehicles in October 2020. We requested that Suzuki should implement the update in the UK on the affected Suzuki Vitara model and other similar vehicles, including the SX4 and S-Cross via a non-safety recall campaign to ensure maximum uptake of this improvement to the real world vehicle emissions.

This was implemented under DVSA recall reference number R/2021/059, contacting all owners to request they arrange to have the software update applied to their vehicles.

Despite the positive outcome in rectifying non-compliant strategies related to NSC control, we continue to have concerns over the emissions strategy relating to EGR operation used within this vehicle. Findings from our testing relating to EGR operation have been shared with the granting type approval authority and discussions remain underway with Suzuki to understand the justification for this strategy.

These tests were carried out before the Court of Justice of the EU judgement in case C-693/18 and subsequent related cases. The findings in this report are based on the legislation in place at the time of the investigation.

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Make: Volkswagen

Model: Passat (2017MY)

Engine and fuel type: 1598cc Diesel

Transmission: Automatic

Emission standard: Euro 6b

Test reference: 29515

Tested: February 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The Volkswagen Passat initially failed but following work to rectify the fault this vehicle was found to be compliant with all required tailpipe pollutant emission limits under the NEDC cold legislative test.

The initial NEDC lab tests resulted in particle numbers (PN) above legislative limits and carbon dioxide (CO2) emissions above declared figures. Multiple tests were conducted due to the unexpectedly high PN with only the fourth test showing borderline PN compliance. The vehicle's stop-start technology was not active on the tests. We consider CO2 results would most likely have been within 10% of the declared value had this been active.

The PN was high in all tests, which warranted further discussion with the manufacturer.

In respect to WLTC track testing, PN continued to be higher than expected. A second WLTC track test was completed due to an error in recording the carbon monoxide (CO) emission from the first test. Analysis of exhaust temperature data from RDE and WLTC track tests does not suggest diesel particulate filter (DPF) regeneration events had occurred.

Volkswagen stated they were surprised at how poor the vehicle's PN results were following our tests. They shared test results with us from 2 other Passat models, including one using the same software as the vehicle we tested. All tests were below the legal limit for PN.

Volkswagen were unable to explain the difference but suggested that the DPF may have a crack. They requested the vehicle to be retested with a new DPF fitted and offered to analyse the data with us. We agreed to this, and that Volkswagen would prepare the vehicle for an NEDC cold test once the DPF had been replaced.

Following the retest, PN numbers dropped significantly and were within the legal limit.

Volkswagen identified that the original DPF as fitted to the test vehicle did have a small crack at the exit end of the DPF, which explained the high PN values. Volkswagen believed that the crack would have occurred at high temperatures, such as during motorway driving.

This discovery concerned us as the DPF cracking found in the test vehicle was likely to be inherent in other Volkswagen vehicles employing the same aftertreatment system. We requested Volkswagen take immediate action to counter this problem.

Volkswagen confirmed 14,360 VW Passat vehicles and 3,980 SKODA Superb 1.6TDI models could be affected.

Volkswagen have announced they will be contacting customers of affected Volkswagen Passat and SKODA Superb models informing them to book their vehicles in to receive the software updates and undergo checks of the DPF and exhaust gas circulation (EGR).

From the results of both legislative and non-legislative testing, we do not have reason to believe that the Volkswagen Passat tested was non-compliant with its legal emissions performance requirements.

Tests run with original diesel particulate filter (DPF):

Tests run with replacement diesel particulate filter (DPF):

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In this section:

You can download the unprocessed raw data showing the results of each test that was conducted on these vehicles.

Download ‘Car (petrol) data, 2019’ (ZIP, 127 MB)

Make: BMW

Model: 118i Sport (2018MY)

Engine and fuel type: 1499cc 100kW Petrol

Transmission: Manual 6 speed

Emission standard: Euro 6d-temp

Test reference: 29514

Tested: January 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

vehicle preparation inspection

The BMW 118 was compliant with all required tailpipe pollutant emission limits under the WLTC cold and RDE legislative tests.

From the results of both legislative and non-legislative testing, we do not have reason to believe that the BMW 118 tested was non-compliant with its legal emissions performance requirements.

Make: Dacia

Model: Duster

Engine and fuel type: 1598cc Petrol

Transmission: Manual 5 speed

Emission standard: Euro 6b

Test reference: 29512

Tested: March 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The Dacia Duster was compliant with all required tailpipe pollutant emission limits under the NEDC cold legislative test.

The WLTC track tests resulted in high carbon monoxide (CO) emissions, which warranted further discussion with the manufacturer.

Dacia explained the higher than expected CO emissions occurred during the extra-high speed phase of the WLTC track test. In order to meet the speed required at the extra-high speed phase, high power was needed from the engine.

For this engine, fuel enrichment occurs at engine power above 40 to 45 kW, and this threshold was exceeded during the extra-high speed phase of the WLTC track test. Therefore, Dacia consider the Duster CO emission results were affected by fuel enrichment occurring and stated this fuel enrichment strategy is needed for thermal protection of the engine.

We accept such strategies may be permitted where there is a risk of damage to the engine or exhaust components, however their use should be minimised in order to limit excessive emissions during normal driving.

From the results of both legislative and non-legislative testing, we do not have reason to believe that the Dacia Duster was non-compliant with its legal emissions performance requirements.

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Make: Fiat

Model: Tipo (2017MY)

Engine and fuel type: 1499cc 70kW Petrol

Transmission: Manual 6 speed

Emission standard: Euro 6b

Test reference: 29474

Tested: March 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The Fiat Tipo was compliant with all required tailpipe pollutant emission limits under the NEDC cold legislative test.

The NEDC lab tests resulted in carbon dioxide (CO2) emissions above declared figures, which warranted further discussion with the manufacturer.

The vehicle was initially tested at 1360kg inertia test weight. We retested at 1250kg after speaking to Fiat as they advised we had identified the wrong test weight in our original test. This retest did not show a significant improvement in CO2.

During our discussions with them, Fiat suggested that the high levels of CO2 could be a result of:

Of particular interest here was the gear shift pattern. During type approval, Fiat used second gear for vehicle pull away rather than first gear, whereas our tests used first gear.

Fiat explained that the Tipo tested is the entry-level version and the power to weight ratio is low. To overcome this, Fiat used short gear ratios and a 6-speed transmission. They added first gear is very short and if it is used on the NEDC test it will use much higher engine speed than is typical when compared to driving in natural conditions.

The CO2 value declared is lower than we found during testing and we acknowledge the alternative gear shift pattern described above is likely the most significant reason for this. Degraded real-world CO2 performance can be expected if not following this gear shift pattern.

From the results of both legislative and non-legislative testing, we do not have reason to believe that the Fiat Tipo tested was non-compliant with its legal emissions performance requirements.

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Make: Jeep

Model: Renegade (2015MY)

Engine and fuel type: 1368cc 100kW Petrol

Transmission: Automatic

Emission standard: Euro 6b

Test reference: 30158

Tested: July 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The Jeep Renegade was compliant with all required tailpipe pollutant emission limits under the NEDC cold legislative test.

The NEDC cold test resulted in carbon dioxide (CO2) emissions above legislative limits and WLTC track tests resulted in high carbon monoxide (CO) emissions. Therefore, further discussion with the manufacturer was held.

Jeep suggested the combination of stop-start not working, alternator charge rate being high and test dynamics would bring the NEDC CO2 result to within around 10% of the Certificate of Conformity (COC) declared number.

When questioned specifically over the high CO on the WLTC track test, Jeep stated fuel enrichment, used for component thermal protection, would contribute to high CO.

From the results of both legislative and non-legislative testing, we do not have reason to believe that the Jeep Renegade was non-compliant with its legal emissions performance requirements.

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Make: KIA

Model: Cee’d GT Line ISG (2018MY)

Engine and fuel type: 998cc G3LC-6I 88.3kW Petrol

Transmission: Manual 6 speed

Emission standard: Euro 6b

Test reference: 29807

Tested: January 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The Kia Cee’d delivered high carbon dioxide (CO2) and moderately high particulate matter (PM) results under the NEDC cold legislative test.

To understand the high PM and CO2 result achieved on the NEDC cold laboratory test, KIA carried out further investigations into the vehicle and noted, in their opinion, the vehicle had at one point been mis-fuelled with diesel. KIA changed the engine oil, filter and, as a precautionary measure, the fuel injectors.

The vehicle was subsequently retested under laboratory conditions and after the first test (cold test 2) the total hydrocarbons (THC) measured on the high end of emission limits. The test was repeated (cold test 3) and the THC emissions results were then below regulation limits.

We acknowledge the non-methane hydrocarbons (NMHC) results were above the legislative limit in cold test 2, despite previously having been within the limit. It was not possible to conduct further testing due to the further analysis KIA was carrying out, but DVSA and KIA expect the THC and NMHC emissions would have stabilised with further vehicle conditioning.

KIA initially informed us it was their intention to carry out an in-depth analysis of the fuel injectors exchanged on this vehicle. However, KIA have since stated due to challenges created by Covid-19 and other business priorities, they no longer plan to complete this analysis. Due to KIA's decision to not carry out an in-depth analysis of the fuel injectors, we are unable to conclude the full root cause.

Upon analysis of the test data KIA noted there were 4 points in the high speed section of the WLTC track test cycle where carbon monoxide (CO) emissions were high. KIA explained that these peaks were likely the result of high engine load, which would have led to the exhaust temperature increasingly significantly.

To protect the engine components during these conditions, the control strategy includes fuel enrichment which decreases the air-to-fuel ratio (AFR), which lowered the exhaust gas temperature but as a result increases CO emissions. KIA stated the AFR only deviated for a very small amount of time and such fuel enrichment strategies were permitted in type approval.

Kia further stated the unusually high engine load during the WLTC track test had not been experienced by KIA during product development but they hypothesised that the additional weight of the portable emissions measurement system (PEMS) kit along with a potentially high electrical load (for example, if the headlights or air conditioning had been turned on) could be contributory factors.

We asked KIA if they were making further changes to their Euro 6d-temp vehicles to mitigate against the high exhaust temperatures. KIA said they were not but noted the vehicle showed compliance when tested against RDE requirements.

From the results of both legislative and non-legislative testing, we do not have reason to believe that the Kia Cee’d tested was non-compliant with its legal emissions performance requirements.

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Make: Porsche

Model: Panamera (2017MY)

Engine and fuel type: 2894cc 324kW Petrol

Transmission: Automatic

Emission standard: Euro 6b

Test reference: 30041

Tested: March 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The Porsche Panamera was compliant with all required tailpipe pollutant emission limits under the NEDC cold legislative test.

These tests showed elevated levels of carbon monoxide (CO) during RDE and WLTC track testing. These points warranted further discussion with the manufacturer.

Porsche's response was that the our NEDC cold CO test result was a result they would expect for a vehicle with a significantly higher mileage than a new vehicle used for a type approval. However, they stated that our RDE CO test results were not in line with what they would expect.

Porsche noted the RDE test was performed at low ambient temperature and with a cold start, which may have impacted catalyst functionality. In particular, they noted the catalyst may have needed more time to achieve an appropriate operating temperature and may have cooled down below the appropriate operating temperature during low-load driving intervals.

However, Porsche's overall conclusion was the test results indicated a potential vehicle defect and provided data to suggest the elevated level of CO was likely to be a specific vehicle issue and not systemic.

Unfortunately, Porsche were unable to inspect the test vehicle for potential technical issues, such as leakages in the exhaust system, as it had since suffered damage.

From the results of both legislative and non-legislative testing, we do not have reason to believe that the Porsche Panamera tested was non-compliant with its legal emissions performance requirements.

These tests were carried out before the Court of Justice of the EU judgement in case C-693/18 and subsequent related cases.The findings in this report are based on the legislation in place at the time of the investigation.

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Make: Renault

Model: Captur

Engine and fuel type: 898cc Petrol

Transmission: Manual

Emission standard: Euro 6c

Test reference: 29473

Tested: January 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The Renault Captur was compliant with all required tailpipe pollutant emission limits under the WLTC cold and RDE legislative tests.

From the results of both legislative and non-legislative testing, we do not have reason to believe the Renault Captur tested was non-compliant with its legal emissions performance requirements.

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Make: Skoda

Model: Karoq SE TSi

Engine and fuel type: 999cc 85kw Petrol

Transmission: Manual 6 speed

Emission standard: Euro 6b

Test reference: 29937

Tested: April 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The Skoda Karoq was compliant with all required tailpipe pollutant emission limits under the NEDC cold legislative test.

From the results of both legislative and non-legislative testing, we do not have reason to believe that the Skoda Karoq tested was non-compliant with its legal emissions performance requirements.

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Make: Subaru

Model: Forester 2.0i-L Eyesight (2018MY)

Engine and fuel type: 1995cc 110kW Petrol

Transmission: Automatic

Emission standard: Euro 6b

Test reference: 29878

Tested: February 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The Subaru Forester was compliant with all required tailpipe pollutant emission limits under the NEDC cold legislative test.

The RDE on-road test and WLTC test conducted on a test track both resulted in very high emissions of carbon monoxide (CO). Carbon dioxide (CO2) emissions were also consistently above declared figures, which warranted further discussion with the manufacturer.

Subaru explained that the high emissions of CO during on-road and track testing were due to the use of a fuel enrichment strategy intended to prevent thermal damage to components in the exhaust after-treatment system. This explanation aligned with our further analysis and we concluded that there was not sufficient evidence to indicate non-compliance of this emission strategy.

From the results of both legislative and non-legislative testing, we do not have reason to believe that the Subaru Forester tested was non-compliant with its legal emissions performance requirements. Subaru has outlined that significant improvements have been made to the CO emissions of its latest vehicles conforming to the Euro 6d emission standard.

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Make: Volvo

Model: V40

Engine and fuel type: 1969cc Petrol

Transmission: Manual 6 speed

Emission standard: Euro 6d-temp

Test reference: 29806

Tested: February 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The Volvo V40 was compliant with all required tailpipe pollutant emission limits under the WLTC cold and TDE legislative tests.

From the results of both legislative and non-legislative testing, we do not have reason to believe that the Volvo V40 tested was non-compliant with its legal emissions performance requirements.

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In this section:

You can download the unprocessed raw data showing the results of each test that was conducted on these vehicles.

Download ‘Light van data, 2019’ (ZIP, 138 MB)

Make: Citroen

Model: Berlingo 1.6 Blue HDi 75 (2018MY)

Engine and fuel type: 1560cc 55kw Diesel

Transmission: Manual 5 Speed

Emission standard: Euro 6b

Test reference: 29805

Tested: January 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The Citroen Berlingo was compliant with all required tailpipe pollutant emission limits under the NEDC cold legislative test.

NEDC lab tests resulted in carbon dioxide (CO2) emissions above declared figures and WLTP track tests resulted in higher than expected nitrogen oxides (NOx), which warranted further discussion with the manufacturer.

Our analysis of the tests did not find any specific anomalies or errors that may have led to the high NOx and CO2 being recorded and Citroen were asked to analyse the test results. Citroen commented that dynamic test cycles would deliver higher NOx results compared to their own customer data.

Under the request of Citroen, the vehicle was retested by us and the WLTC track test results were similar to the original test results. Test data was again shared with Citroen, and Citroen requested to take ownership and test the vehicle. 

Citroen testing showed an excellent correlation to our data and led Citroen to conclude that the WLTC track test procedure we used is more severe than their customer driving average. They further commented that if this vehicle is driven on relatively short trips with high payload and driving dynamically, it has a significant negative impact on both NOx and CO2.

We agree that the higher than expected NOx figures, in particular for the Track WLTC test, are a result of a relatively short trip, with a dynamic drive cycle and vehicle test weight approaching the gross vehicle weight (GVW). However, it is neither unreasonable nor uncommon to see such vehicles undertaking this type of drive cycle.

From the results of both legislative and non-legislative testing, we do not have reason to believe that the Citroen Berlingo tested was non-compliant with its legal emissions performance requirements.

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Make: Fiat

Model: Doblo 16V SX Multijet II (Registered 2017)

Engine and fuel type: 1248cc 70kW Diesel

Transmission: Manual 5 speed

Emission standard: Euro 6b

Test reference: 30286

Tested July 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The Fiat Doblo was subject to 2 regulatory NEDC cold laboratory tests during the course of our testing. Emissions of nitrogen oxides (NOx) and other criteria pollutant emissions were compliant with legislative limits for both tests, whilst measured carbon dioxide (CO2) figures were higher than those declared by the manufacturer at the point of approval.

The measured CO2 levels during regulatory testing and high levels of NOx emissions within non-regulatory testing were discussed further with the manufacturer.

Fiat discussed a range of potential reasons for the slightly higher than expected CO2 emissions during our regulatory testing. Following consideration of the reasons set out by Fiat, we were satisfied that Fiat had provided feasible reasons for measured CO2 figures being higher than declared values.

As a result of further discussions with Fiat on the high real-world NOx emissions of this vehicle and the Fiat 500X (report 30245) during non-regulatory testing,

2 areas of concern relating to the emission strategy used within the vehicle were identified.

These strategies related to the reduced effectiveness of NOx emissions control by the NOx storage catalyst (NSC) and exhaust gas recirculation (EGR) during extended periods of driving. Further testing and analysis of the vehicle's software was conducted by us to better understand the strategies being used.

Through parallel investigations of the Fiat 500X, which shares a common engine platform and calibration, we were able to assess the improvement in emissions performance over an extended steady-state test cycle and over the legislative laboratory test after application of the updated software. The updated software resulted in a significant improvement in NOx emissions over extended testing, without compromise to CO2 or other criteria emissions, and analysis of the updated software showed that the non-compliant strategy was no longer present.

We requested that Fiat implemented the software update in the UK on the affected Fiat Doblo vehicles via a non-safety recall campaign to ensure maximum uptake of this improvement to the real-world vehicle emissions. This was implemented by Fiat within the UK as DVSA reference number NC/2021/011 in August 2021, contacting all owners to request they arrange to have the software update applied to their vehicles.

We continue to have concerns over the emissions strategy relating to EGR operation. Findings from our testing relating to EGR operation have been shared with the granting type approval authority and discussions remain underway with Fiat to understand the justification for this strategy.

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Make: Nissan

Model: NV300 (2018MY)

Engine and fuel type: 1598cc 92kW Diesel

Transmission: Manual

Emission standard: Euro 6b

Test reference: 29935

Tested: April 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The Nissan NV300 was compliant with all required tailpipe pollutant emission limits under the NEDC cold legislative test.

The NEDC tests resulted in carbon dioxide (CO2) emissions above declared figures, however stop-start technology was not active on the laboratory tests and if this had been active, we predict the CO2 results would have been in line with the declared value of 159g/km.

When conducting the WLTC track tests, the nitrogen oxides (NOx) emissions results were higher than expected for this class of vehicle.

On investigation of the test data, a diesel particulate filter (DPF) regeneration event may have been initiated and interrupted towards the end of the RDE test. However, this does not appear to have had a significant impact on the NOx emission result. We asked Nissan to review the data and explain the results.

Nissan explained the laboratory NEDC hot NOx results were possibly due to high engine intake temperatures experienced at the start of the cycle, which reduced the exhaust gas recirculation (EGR) rate. This reduction in the EGR rate may have increased NOx emissions beyond the capability of the selective catalytic reduction (SCR), which would not be operating at its optimum temperature, resulting in increased tailpipe NOx emissions.

With regards to the WLTC track NOx emissions, Nissan commented that these were as expected.

From the results of both legislative and non-legislative testing, we do not have reason to believe that the Nissan NV300 tested was non-compliant with its legal emissions performance requirements.

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Make: Renault

Model: Master (2017MY)

Engine and fuel type: 2298cc 96kW Diesel

Transmission: Manual

Emission standard: Euro 6b

Test reference: 29513

Tested: February 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The Renault Master was compliant with all required tailpipe pollutant emission limits under the NEDC cold legislative test.

From the results of both legislative and non-legislative testing, we do not have reason to believe that the Renault Master tested was non-compliant with its legal emissions performance requirements.

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Make: Volkswagen

Model: Transporter T30 (2018MY)

Engine and fuel type: 1968cc 75kW Diesel

Transmission: Manual 5 speed

Emission standard: Euro 6b

Test reference: 29936

Tested: July 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The Volkswagen Transporter was compliant with all required tailpipe pollutant emission limits under the NEDC cold legislative test.

The NEDC lab tests resulted in carbon dioxide (CO2) emissions above declared figures, which warranted further discussion with the manufacturer.

Volkswagen provided reasons for why our test results differed from their own. These included:

The reasons provided by Volkswagen are broadly in line with our technical understanding and when these assumptions are applied the CO2 results would fall within 10% of the manufacturer's declared figure of 156g/km.

From the results of both legislative and non-legislative testing, we do not have reason to believe that the Volkswagen Transporter tested was non-compliant with its legal emissions performance requirements.

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In this section:

You can download the unprocessed raw data showing the results of each test that was conducted on these vehicles.

Download ‘HGV data, 2019’ (ZIP, 38.7 MB)

Make: DAF (2016MY)

Model: LF 180FA

Engine and fuel type: 4500cc, Diesel

Transmission: Manual

Emission standard: Euro 6 Step A

Test reference: 29649

Tested: December 2018

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The DAF LF initially failed but with additional testing this vehicle was found to be compliant with all required tailpipe pollutant emission limits under the on-road conformity legislative test.

Initial on-road conformity tests resulted in nitrogen oxides (NOx) emissions above legislative limits, which warranted further discussion with the manufacturer.

DAF's engine supplier Cummins reviewed the test data provided from our tests along with their historical data for the particular engine model tested and similar models.

Cummins observed from the data provided a difference in the amount of time the vehicle spent at 0 speed (such as the engine at low idle) during the 2 tests. This difference in time spent at low idle appeared to have had an impact on the temperature in the exhaust stream. This suggested there would have been a difference in SCR Catalyst temperature and hence the ability of the catalyst to convert NOx.

Cummins’ assessment was that this was potentially the main cause of the difference in NOx results between the two tests. Cummins requested the vehicle to undertake additional testing in order to deliver definite conclusions. 

With regards to the impact of ‘driving style’, Cummins evaluated the differences between the two tests in terms of the 3 key parameters that typically impact tailpipe NOx.

These parameters were:

Cummins recognised that the above effects result in some variation in NOx emission results.

As European emissions regulations have advanced, Cummins have developed their products in line with the increasing stringency. Recent developments for Euro 6 Step D engines include a higher maximum temperature for the operation of the SCR thermal management and activation of the SCR thermal management sooner.

Cummins were asked to consider recalibrating their Step A products, such as the test vehicle with their improvements developed for Step D and they agreed. This will improve NOx emissions of existing vehicles to different driving styles and route conditions.

Consequently, DAF/Cummins released new software and calibration for its Step A and Step C products to increase NOx control. The manufacturer will work in collaboration with DVSA to maximise the recalibration take up rate.

Unfortunately, due to vehicle availability there was not an opportunity for us to re-test the proposed update, however a similar vehicle was selected for the 2021 campaign to confirm compliance.

From the results, and following the recalibration activities, we do not have reason to believe that the DAF LF tested is non-compliant with its legal emissions performance requirements.

Conformity factor result using CO2 window calculation method:

Conformity factor result using work window calculation method:

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Make: IVECO

Model: Eurocargo (2016MY)

Engine and fuel type: 6728cc, Diesel

Transmission: Automatic

Emission standard: Euro 6 Step A

Test reference: 29940

Tested: March 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The IVECO Eurocargo initially failed but with additional testing this vehicle was found to be compliant with all required tailpipe pollutant emission limits under the on-road conformity legislative test.

The initial on-road conformity tests resulted in nitrogen oxides (NOx) emissions above the legislative limits which warranted further discussion with the manufacturer.

The vehicle was investigated and retested by IVECO. This initial retesting showed good emission performance and high NOx conversion efficiency when compared to our tests.

Following further testing and analysis, emission compliance was verified by IVECO across several portable emissions measurement system (PEMS) tests. IVECO attributed the root cause of the emission variability between our tests and IVECO's tests, and closeness to exceeding the NOx conformity factor, to the relatively simple exhaust aftertreatment temperature control via an exhaust throttle. IVECO stated that this in combination with certain test cycles or routes, could lead to low selective catalytic reduction (SCR) NOx conversion efficiency.

Our data analysis of the tests conducted confirmed IVECO's conclusion of variability in exhaust gas temperature and the potential negative impact on SCR NOx conversion efficiency.

From the results obtained, we cannot reach the conclusion that the Iveco EuroCargo tested was non-compliant. However, the results demonstrated a level variability of the permitted NOx conformity factor limit. Therefore, we have contacted the granting type approval authority so that it can be considered as part of their ongoing In-Service Conformity obligations.

Conformity factor result using CO2 window calculation method:

Conformity factor result using work window calculation method:

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Make: Mercedes-Benz

Model: Actros N3 Rigid (2018MY)

Engine and fuel type: 7698cc, 175kW Diesel

Transmission: Automatic

Emission standard: Euro 6 Step C

Test reference: 29737

Tested: January 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The Mercedes Actros was compliant with all required tailpipe pollutant emission limits under the on-road conformity legislative test.

When we tested the vehicle to the EU Heavy Duty RDE protocol as part of the on-road conformity test, we found compliance for total hydrocarbons (THC), carbon monoxide (CO) and nitrogen oxides (NOx) emissions. All monitored emissions fell well below the test limits.

From the results, we do not have reason to believe that the Mercedes Actros tested was non-compliant with its legal emissions performance requirements.

Conformity factor result using CO2 window calculation method:

Conformity factor result using work window calculation method:

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In this section:

You can download the unprocessed raw data showing the results of each test that was conducted on these vehicles.

Download ‘PSV data, 2019’ (ZIP, 222 MB)

Make: Mercedes-Benz

Model: Citaro (2015MY)

Engine and fuel type: 6370cc OM936 6 cylinder 220kW Diesel

Transmission: Automatic

Emission standard: Euro 6 Step A

Test reference: 29812

Tested: January 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The Mercedes-Benz Citaro was not compliant with all required tailpipe pollutant emission limits under the on-road conformity legislative test.

On-road conformity tests resulted in nitrogen oxides (NOx) emissions above legislative limits, which warranted further discussion with the manufacturer.

Initial meetings were held with Mercedes-Benz and subsequently the German type approval authority (KBA) to discuss the results and agree the investigation plan and actions. Mercedes-Benz reviewed and confirmed that the 2 tests we conducted had been completed correctly but the results were not aligned to their experience of In-Service Conformity testing for this family of engine.

Our initial inspection of the vehicle showed no obvious issues, however it was noted from interrogation of the aftertreatment system history maps that unexpectedly high temperatures had been observed at the temperature sensor located at the exit of the diesel oxidation catalyst (DOC). It was hypothesised that such high temperatures may have degraded the DOC and selective catalytic reduction (SCR) system, reducing the system NOx conversion efficiency. 

The engine and aftertreatment system were removed from the vehicle and shipped to Mercedes-Benz for further investigation, which initially included the following: 

 The physical inspection of the aftertreatment system revealed that the DOC brick had moved inside the canning and had impacted the temperature sensor, causing it to bend out of position. The incorrect position of the sensor could then lead to incorrect temperature readings and when the diesel particulate filter (DPF) underwent regeneration, the DOC was subject to higher-than-expected temperatures. This correlated with the initial hypothesis of aftertreatment system degradation and reduced NOx conversion efficiency.  

The engine and aftertreatment system were installed on an engine test dynamometer and the emission performance investigated. The investigation confirmed that the engine out emissions (pre aftertreatment) were low and in line with Mercedes-Benz expectation and type approval values. However, the tailpipe emissions (post aftertreatment) were high and correlated well with the vehicle PEMS testing conducted. The testing also confirmed that whilst the NOx levels were high they were below the on-board diagnostic threshold limit of 1.5g/kWh, hence there were no fault codes or malfunction indicator light illumination in the vehicle. 

The aftertreatment system performance was compared to a Mercedes-Benz reference system that had completed 2,000 hours of durability testing. The analysis concluded the DOC capacity to oxidise nitric oxide (NO) to nitrogen dioxide (NO2) was significantly reduced. The ratio of NO:NO2 is particularly important for the downstream SCR NOx conversion efficiency, a lower percentage of NO2 leading to lower NOx conversion efficiency. 

The SCR system was sent to the supplier for post-mortem analysis. The analysis found significant areas of concern with both material integrity and NOx conversion efficiency. 

The combination of the displaced DOC brick, bent temperature sensor and elevated exhaust gas temperatures confirmed the hypothesis that high temperatures degraded the DOC and SCR system, reducing the system NOx conversion efficiency and leading to the NOx emission failure. 

The root cause for the displaced DOC brick was attributed to manufacturing and supplier variability. As the components were no longer in production, a service fix and instruction had been released consisting of a band clamp that could be fitted in-between the DOC and DPF to prevent movement of the DOC brick. 

Midway through discussions and investigations, Mercedes-Benz informed the German type approval authority (KBA) of the work being undertaken with us, which instigated a parallel testing activity led by KBA. An equivalent age and mileage Citaro bus was tested over an RDE compliant route around Regensburg. The results achieved compliant emissions results based upon 3 tests. 

Following extensive testing and analysis including the involvement of the Type-Approval Authorities (TAA) conducting their own investigation, it was concluded that the aftertreatment system had experienced degradation of performance to such an extent that NOx emissions exceeded the maximum allowable conformity factor.  

The root cause of the degradation was attributed to manufacturing and supplier variability of the DOC brick canning allowing the brick to move downstream in the can, both degrading the DOC and downstream SCR NOx conversion efficiency. A service fix and dealer instruction are available for vehicles that may experience DOC brick movement. 

 The engine was replaced with a new aftertreatment system on the original test vehicle and the vehicle returned to service. 

Conformity factor result using CO2 window calculation method:

Conformity factor result using work window calculation method:

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Make: Optare

Model: Solo (2015MY)

Engine and fuel type: OM934 5132cc, 4 cylinder, 130kW Diesel

Transmission: Automatic

Emission standard: Euro 6 Step A

Test reference: 29970

Tested: April 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The Optare Solo was not compliant with all required tailpipe pollutant emission limits under the on-road conformity legislative test.

On-road conformity tests resulted in nitrogen oxides (NOx) emissions above legislative limits, which warranted further discussion with the manufacturer and powertrain supplier, Daimler. 

Meetings were held with both Optare and Daimler to discuss the results and agree the investigation process and steps into the high NOx emission. Daimler reviewed and confirmed that the 2 tests we conducted had been completed correctly but the results were not aligned to their experience of In-Service Conformity (ISC) testing for this family of engine.

The initial hypothesis from Daimler was that the vehicle had been run on a fuel with high fatty acid methyl ester (FAME) biodiesel content, exceeding the maximum B7 blend for which the engine and aftertreatment system had been developed and validated, leading to irreversible degradation of the aftertreatment system. 

The engine and aftertreatment system were removed from the vehicle and shipped to Daimler AG for further investigation, which initially included the following: 

The hypothesis that the vehicle had been run on high FAME biodiesel content was investigated by analysis of a fuel sample taken from the bus fuel storage depot. The analysis showed a FAME bio content of 22% supporting the hypothesis.

Aftertreatment system degradation and poisoning due to the presence of alkali metals from the bio diesel esterification process was further hypothesised as the cause of the high NOx emissions. In particular, degradation and poisoning of the diesel oxidation catalyst (DOC), reducing the ability to convert nitric oxide (NO) to nitrogen dioxide (NO2), altering the overall NO:NO2 ratio and in addition degrading the selective catalytic reduction (SCR) system NOx conversion efficiency.

The engine and aftertreatment system were removed from the vehicle, installed on an engine test dynamometer and the emission performance investigated. The investigation confirmed that the engine out emissions (pre-aftertreatment) were low and in line with Daimler expectation and type approval values.

However, the tailpipe emissions (post-aftertreatment) were high and correlated well with the vehicle portable emissions measurement system (PEMS) testing conducted. The testing also confirmed that whilst the NOx levels were high they were below the on-board diagnostic threshold limit of 1.5g/kWh, hence there were no fault codes or malfunction indicator light (MIL) illumination in the vehicle. 

The aftertreatment system was removed from the engine test dynamometer and sent to the supplier for post-mortem analysis. The analysis focused upon the SCR system performance and found significant areas of concern with the material integrity, oxygen storage capacity and NOx conversion efficiency. 

The combination of fuel analysis with engine and aftertreatment test and analysis confirmed the hypothesis that use of high percentage FAME biodiesel degraded the aftertreatment system to such an extent that the NOx emissions failed to meet the allowable emission conformity factor. 

The agreement to run biodiesel blends greater than B7 on the Optare Solo product line was disputed by Optare and Daimler throughout the investigation. However, it was confirmed that the vehicle tested had been run on fuel blends of around B20 for periods of its service life and from test and analysis the aftertreatment system had experienced degradation of performance to such an extent that NOx emissions exceeded the maximum allowable conformity factor.

The engine and aftertreatment system were replaced with new units and the vehicle returned to the owner.

Another Optare Solo vehicle was added to a future DVSA program to check emission conformity with a vehicle that had been run on fuel that complied to a maximum bio blend content of B7.

Conformity factor result using CO2 window calculation method:

Conformity factor result using work window calculation method:

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Make: Volvo

Model: Sunsundegui (2015MY)

Engine and fuel type: 10838cc, Diesel

Transmission: Automatic

Emission standard: Euro 6 step B

Test reference: 29810

Tested: February 2019

The following tests were completed on this vehicle to assess the emission control systems and tailpipe emissions:

The Volvo Sunsundegui initially failed but following work to rectify a fault this vehicle was found to be compliant with all required tailpipe pollutant emission limits under the on-road conformity legislative test.

The initial on-road conformity tests resulted in nitrogen oxides (NOx) emissions above legislative limits, which warranted further discussion with the manufacturer.

Volvo noted the results were ‘unexpectedly high’ and provided evidence of 2 other buses with D11 EUVI step B engines previously tested in Sweden within the Volvo In-Service Conformity program which showed much lower NOx emissions.

Volvo's initial main hypothesis for the high NOx values was a lack of urea being introduced into the selective catalytic reduction (SCR) system, which could be the result of a partially blocked dosing valve. They noted in addition to a potential dosing valve issue, they could not rule out premature deterioration of the SCR system.

Volvo also provided additional potential causes for the high NOx and requested to examine the vehicle to establish which of these or other faults may be causing this issue.

Volvo investigated multiple causes and some changes were made to the vehicle. All work was observed by our engineers. A repeat emission test was conducted (test 3) and witnessed by Volvo. However, it showed little improvement.

The emission result seemed to suggest the poor NOx performance was due to SCR degradation. Our analysis of the second-by-second NOx emission trace also supported the theory the SCR system had prematurely degraded in some way.

Volvo subsequently confirmed the SCR had degraded and have put in place an approved action plan to resolve this issue.  

A repeat emission test was conducted (test 4) following the replacement of the aftertreatment system and the NOx conformity factor and emissions were compliant.

From the results, we do not have reason to believe that the Volvo Sunsundegui tested was non-compliant with its legal emissions performance requirements.

Conformity factor result using CO2 window calculation method:

Conformity factor result using work window calculation method:

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This annex explains some of the emissions reductions technologies mentioned in the report.

Exhaust gas recirculation (EGR) displaces intake air with a defined amount of inert exhaust gas.The presence of inert exhaust gas in the combustion chamber reduces both peak combustion temperatures and the amount of oxygen available. This in turn reduces formation of nitrogen oxides (NOx), but can also cause an increase in the emissions of particulate matter (soot).

EGR has been used for many years on both light-duty and heavy-duty engines. Use of EGR may lead to compromises on other vehicle characteristics, such as:

However, a well-designed and calibrated EGR system should minimise any negative impacts.

There are a number of types of EGR system available to manufacturers including:

This occurs within the combustion chamber or exhaust manifold interface, and is set by the timing of the closing of the exhaust valve.

Following the completion of the exhaust stroke, the exhaust valve remains open during the start on the induction stroke, causing some of the exhaust in the exhaust manifold to be drawn back into the combustion chamber. As there is no additional control over this, the amount of EGR that occurs is generally kept low.

Some of the exhaust gas is directed through a pipe from the exhaust system back into the inlet manifold.

The EGR flow is regulated by an EGR valve, and is set according to a range of engine operating conditions and parameters which are controlled by the ECU software and calibration.

‘High pressure’ EGR systems take exhaust gas from before the turbocharger. For some Euro 6 vehicles, ‘low pressure’ EGR systems have been introduced, which takes exhaust gas from after the diesel particulate filter and introduces it into the intake system. Often high pressure and low pressure EGR are used in combination.

This is the same as external EGR, but the recirculated exhaust gases pass through a cooler before re-entering the engine. This allows EGR to be applied over a wider range of engine operating conditions, and can provide a further reduction in the combustion temperature.

A diesel oxidation catalyst (DOC) promotes the oxidation of several of the exhaust components. These are oxidised using oxygen that is present in the diesel exhaust, in the presence of a catalyst. The components include:

In addition to targeting regulated pollutants, a DOC can also control several non-regulated HC species, such as aldehydes and polycyclic aromatic hydrocarbons (PAHs), as well as reducing the odour of the exhaust.

DOCs can also oxidise nitric oxide (NO) exiting the engine into nitrogen dioxide (NO2). If a DOC is used on its own, this increase in the more harmful nitrogen dioxide can have a negative impact on air quality. However, generation of NO2 may prove to be a benefit when used prior to a diesel particulate filter (DPF) or selective catalytic reduction (SCR), by helping regeneration in a DPF and enhancing the emissions conversion performance of a SCR.

A diesel particulate filter is a device to trap the particulate matter from the exhaust gas of a diesel engine.

They generally consist of some form of filter material which traps the particles as the exhaust flows through it. During use, soot accumulates in the filter, increasing the back pressure in the exhaust. To allow continued efficient operation, accumulated soot needs to be regularly removed. This can be achieved on the vehicle by a process known as regeneration.

There are a number of ways to achieve this, including:

The alternative to on-board regeneration is to remove the DPF from the vehicle, though this is often impractical and is not a common solution.

Unlike a petrol engine, a diesel engine's combustion process and exhaust gas is ‘lean’, which means it has excess oxygen present. As a result, a standard diesel oxidation catalyst cannot convert NOx (nitric oxide and nitrogen dioxide) emissions.

A lean NOx trap is a device which looks similar to a standard diesel oxidation catalyst that acts as a molecular sponge, chemically trapping NOx emissions (by adsorption) rather than converting them. They are a type of NOx Storage Catalyst (NSC).

The amount of NOx a trap can hold is dependent on its temperature as well as other constituents such as sulfur. The optimum temperature window is typically around 250 to 450°C. However, once the trap is full, it cannot adsorb any more NOx. The trap must therefore be periodically ‘purged’ by briefly creating ‘rich’ conditions (excess fuel) in the exhaust.

When this happens, the trap releases and simultaneously converts the NOx to nitrogen and water vapour, a process often termed "deNOx". The frequency with which this happens will depend on the system and the driving conditions, but can be several times an hour.

Selective catalytic reduction (SCR) is an alternative catalyst system that is able to convert NOx (nitric oxide and nitrogen dioxide) even under ‘lean’ exhaust gas conditions.

The reaction takes place with ammonia (typically supplied as AdBlue) in the presence of a catalyst, which is either oxides of base metals (such as copper, iron, vanadium, molybdenum and tungsten), zeolites, or various precious metals.

To be efficient, the SCR must be at its nominal operating temperature (typically 250 to 450°C) and it can reduce NOx emissions by up to 95%. Critically, unlike the other systems described here, SCR relies on a consumable reagent (that provides the ammonia) and only reduces emissions whilst the catalyst is being supplied or "dosed" with this reagent. Urea has the trade name of AdBlue, and is also known as Diesel Exhaust Fluid (DEF).

As a result, regulations require:

The temperature of the SCR is determined primarily by the exhaust gas. Therefore, the placement of the SCR in relation to the engine and the engine's duty cycle are critical with respect to the SCR's performance. The SCR canister is relatively large. In addition to the SCR, the following are also required:

Although readily available, the main design constraint is the amount of space needed for the installation.

SCR requires ammonia, which is derived from the urea. The ideal ratio of ammonia to NOx is 1:1.

Under certain conditions, such as low efficiency, extreme low temperature, extreme high temperature, and high mass flow, not all of the ammonia might be used in the NOx reduction process, and some of it may exit the SCR. This is known as ammonia slip.

To prevent the release of ammonia at the tailpipe, an additional catalyst is placed immediately after the SCR. There are various terms for these devices, including:

Any ammonia can either be oxidised to NOx, which is not really desirable, or it can be selectively oxidised to produce water and nitrogen. The ammonia catalyst is often packaged in the same can as the SCR.

Almost all diesel engines these days are turbocharged. The resulting emissions will be dealt with using a combination of techniques. This commonly includes:

Gasoline particulate filters (GPF) have been introduced to reduce particle number emissions from gasoline direct injection (GDI) vehicles. The filters use wall-flow substrates that were first developed for diesel particulate filters.

The GPF regenerates passively, but an active regeneration assist is needed to prevent filter plugging during low temperature duty cycles.

Port fuel injection (PFI) injects fuel into the intake ports just upstream of each cylinder's intake valve.

The main advantage of PFI when compared to direct injection is the extra time allowed for fuel and air mixing, delivering a more homogenous air and fuel mixture.

Aftertreatment or auxiliary hydrocarbon injector (AHI) is a fuel injector located in the exhaust upstream of the diesel oxidation catalyst (DOC) and diesel particulate filter (DPF) and is used to assist with raising the DPF exhaust gas inlet temperature when an active DPF regeneration is required.

These systems are typically employed in heavy duty diesel engines.

Three-way catalytic converters are effective in preventing air pollution from rich-burn and stoichiometric engines fuelled by natural gas, propane and gasoline. Three-way catalysts are designed to perform multiple oxidation reactions and reduction reactions simultaneously to convert air pollutants that are present in the exhaust to harmless gases.

Exhaust gas composition depends on the air to fuel ratio (AFR) at which the engine operates. Rich mixtures (lambda less than 1) produce high concentrations of nitrous oxides (NOx), carbon monoxide (CO) and hydrocarbons (HCs). The exhaust gases of lean fuel mixtures (lambda greater than 1) contain reduced amounts of NOx and HCs.

The three-way reactions take place over specially formulated precious metal catalysts that allow the reduction of NOx by CO and the oxidation of CO and HC by oxygen to occur simultaneously. The catalyst functions most efficiently when the engine oscillates around the stoichiometric point (lambda equal to 1).

Three-way catalysts are typically used with an air to fuel ratio (A/F) controller to maintain a tight control of air fuel ratio (AFR) around stoichiometry. These controllers use a feedback signal from an oxygen sensor located in front of the catalyst and are required for the three-way catalyst to operate properly.

For carbon dioxide (CO2) measurements, there are multiple factors which can contribute to a vehicle's performance when testing in a laboratory.

These include vehicle-based CO2 reducing technologies such as:

Other things that can have an impact are:

For vehicles that were approved under NEDC test procedures, CO2 values obtained under type approval test conditions can be challenging to reproduce.

This can be as a result of ensuring any CO2 reducing technologies deployed are operating in their entirety and as designed. As well as replicating to the full extent the boundary conditions under which the vehicle was type approved.

There are many ways manufacturers can follow regulations to optimise CO2 performance under type approval test conditions. Without having the full scope of test set-up and vehicle preparation information, this adds an additional factor of complexity in a third-party test environment.

The introduction of the WLTP regulation reduced these possibilities, and we observe this in our emissions test programme, where typically CO2 values declared at type approval can be reproduced relatively easily in the same third-party environment.

An emissions conformity factor is a ratio of the respective Type 1 laboratory limit value.

For example: for the Euro 6d emission standard, the M1 category WLTC NOx limit for diesel is 80mg/km. The RDE NOx limit is expressed as conformity factor equal to 1.43, so this will be 1.43 multiplied by 80mg/km, giving a limit value of 114.4mg/km.

This is then applied as the respective NOx limit value for RDE testing.

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