Currently reading: WLTP test: warning that CO2 increases could be higher than expected
Market analyst JATO has warned that increases in CO2 output ratings could exceed predictions when all cars have gone through new tests
Jimi Beckwith
3 mins read
6 August 2018

The difference in CO2 emissions figures of cars tested on the new Worldwide Harmonised Light Vehicle Test Procedure (WLTP) and the outgoing New European Driving Cycle (NEDC) is wider than expected, according to industry analyst JATO. 

The new WLTP test, which is designed to better simulate real-word conditions, comes into force from 1 September. After that date, new cars can only be sold if they have been tested under WLTP. In order to prepare a measurement tool called Co2mpas was developed by the EU Science Hub. The tool calculates the likely change in CO2 emissions to create a 'WLTP correlated' figure.

However, JATO says that the difference in CO2 emissions between cars tested so far and the correlated figures is greater than predicted. In luxury vehicles, the average difference is 18.3g/km higher. That could have major implications for the tax bands that cars are placed in. It could also prove significant because manufacturers will face increasingly stringent fleet average CO2 emissions targets in coming years.


In April, it was predicted that average CO2 figures would rise by around 8g/km. JATO now suggests that this could be as high as 9.6g/km, with the luxury car segment hardest hit. The least-affected segment is city cars, with an average increase of 6.6g/km expected. Volume segments including medium SUVs are hit harder, with a 16.7g/km average increase projected. Emissions of C-segment cars are expected to increase by an average of around 9.6g/km.

A JATO spokesman said: “The impact of re-homologation to WLTP testing could be even higher than previously thought. Following our analysis of a sample of the vehicles currently re-homologated, if this is extrapolated to the whole fleet, CO2 values could reach 130g/km in 2019, which is a significant 12g/km increase on the 118g/km currently seen in Europe and above the target set by the European Union.”

In addition to the discrepancy between predicted figures and the actual WLTP-measured emissions of cars, JATO expressed concern that only around 20% of cars have been re-homologated at present, raising concerns that by the time the switchover to WLTP is enforced, manufacturers may not be prepared.

The spokesman said: “The publication of re-homologated models/versions is not progressing as quickly as expected. It has taken 11 months for 20% of existing models/versions in the market to be re-homologated and published, meaning the industry could face a backlog of vehicles that cannot be registered if it isn’t completed by 31 August.”

This news comes soon after major European car makers protested ever more stringent EU legislation on car emissions, with a fleet average of 95g/km for each car maker coming into force in 2021, as well as a 30% reduction on top of this - or a fleet average of 66g/km - scheduled to come into force by 2030. 

This, combined with the backlash against diesel, which is already contributing to a rise in the average CO2 emissions of cars registered in the UK as more consumers choose petrol-engined cars instead, could push manufacturers into hot water with the EU, which will fine car makers €95 (around £85) per gram over the target per vehicle sold.

“This could amount to a huge financial penalty for the European car industry which registered more than 16 million vehicles in 2017,” said the JATO spokesman. 


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6 August 2018

 Does that mean some Vehicles are paying to much or to little Road Tax....?

6 August 2018

I do like how the report doesn't mention diesel in particular. You mean, the results for ALL cars being sold were underestimated?  OMG. What a surprise! And I thought all the manufacturers were being honest with us.

When the manufacturers themselves are asked to conduct the tests on their own cars what did we actually expect - the truth?

7 August 2018

The results weren't being underestimated per se, simply measured using a driving duty cycle that is not at all representative on modern real-world driving. The old testing methodology used in the UK and Europe, the NEDC, was the product of a different era, designed to be easy to reproduce on the testing equipment of the time it was conceived - passing into EU law in 1970 but having its roots some time prior to that. The duty cycle was designed to be common ground for even the least powerful vehicles then available, and uses only a tiny part of the speed vs acceleration envelope seen in real world driving. For example, in the urban part of the NEDC it takes 26secs to reach 50kph (~30mph). The short extra urban part was later added in the same style. So it is natural that the amount of CO2 and other pollutants produced during such a cycle is much less than real world driving.​The WLTP is closer to real world driving, but is still not fully representative. These cycles provide a common ground to compare one vehicle with another but it is wrong to treat the numbers as absolute, especially as the powertrains in modern cars have a lot of complex air-path and exhaust aftertreatment tech that muddies the waters somewhat when comparing short-duration duty cycles. In Europe at least, there are plans for 'Real Driving Emissions' (RDE) based legislation is beginning to be introduced, made possible by portable gas analyzers, but the results from this type of testing require careful interpretation as no two test cycles will be identical, depending on geography, driving style etc. This type of testing should, however provide an indication of the accuracy of repeatable lab-based testing by comparing on-road performance with the same speed and load cycle 'played back' on a chassis dynamometer (rolling road) in controlled conditions.

As for the 'truthfulness' or otherwise of OEMs in the performance of their vehicles under a very specific test environment, I don't want to comment on malpractive that is much discussed elsewhere. Most but not all of the 'scandals' relate to harmful emissions such as NOx and PM, which on modern vehicles are subject to 'active' exhaust aftertreatment - and thus very hard to test in a fair and representative way. But assuming that this is a challenge that is overcome, it is still only natural to optimise the performance of a vehicle for the benchmark test that will define so much about the marketability of the product in our current legislative and ownership framework. The wisdom of any manufacturer of mainstream vehicles not giving this consideration should probably be questioned. It should also be borne in mind that thanks to the shortcomings of the NEDC in particular, engineering for good performance in emissions testing does not necessarily improve driveability or even real world emissions performance.An interesting aside to this is that the low power requirements (for both accelerating and braking) of the old testing procedures unfairly favour hybrid vehicles which can brake regeneratively. A medium-high power braking event of the kind often seen in the real world will require energy to be dissipated at a much higher rate than can be put into the batteries of most hybrid systems, whereas in the NEDC almost all that energy may be recovered in most cases. Hence some of the biggest discrepencies between NEDC, WLTP and RDE are likely to be seen in HEVs.

6 August 2018

Can we have comparison of the effect on atmospheric vs turbo cars when the scores are in?

I want my NA Flat 6 Cayman back.

6 August 2018

Especially now everybodys been told to buy petrol engined cars

6 August 2018
Time for the European makers to bring on the hybrids and electric vehicles.

7 August 2018

"CO2 output ratings could exceed predictions when all cars have gone through new tests" not sure how a new test means more CO2, it just means you'll be able to more accuratley measure what's produced.

As to "This could amount to a huge financial penalty for the European car industry which registered more than 16 million vehicles in 2017,” said the JATO spokesman or to put it another way 'a huge penalty for our clients'.

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