The first real world CO2 emissions test developed with a carmaker

Speech delivered by Greg Archer, Clean Vehicles Director, at the Geneva Motor Show on March 1st.

The test procedure T&E has jointly developed with PSA, verified by Bureau Veritas, generates a scientifically robust and reproducible figure for the CO2 emissions of the car representative of a typical driver of the model. It is best practice in measuring fuel economy.

The emissions are measured using a Portable Emissions Monitoring System (PEMS). This directly measures the pollution from the exhaust. The PEMS also measures the speed, acceleration and position of the vehicle to ensure the car is driven in a style typical of the driver of the model. There is no electronic connection between the PEMS and the engine management system of the vehicle so the car cannot detect it is being tested. This makes it much more difficult to deploy a defeat device to trick the test and put the car into a low emission mode.

The test itself is conducted on roads to the west of Paris. It has 3 parts, urban, suburban/rural and high speed. Although the route driven is the same the CO2 is calculated for each phase of the test. After the test the overall CO2 figure is calculated using a weighting typical of the average use of the car derived from a PSA database of car usage. We also ensure the vehicle is appropriately loaded based PSA data which shows variations between 1.6 and 2.1 for different models. The test result is also adjusted to account for varying weather conditions, cold starts and diesel particulate filter regeneration events.

The way the car is driven is crucial to the test results. A mix of profession and amateur drivers are used. If the driving style is unrepresentative of the average use of the car the test is rejected and repeated. Several legitimate tests are conducted and early indications are the results reproducible to within 0.1-0.2 l/100km. During the development phase we have been checking the PEMS measurements in a lab using the WLTP cycle and achieved an excellent correlation for diesel cars – further work is ongoing to finalise measurements for petrol vehicles.

To summarise – the test is best practice, scientifically robust, representative of an average driver of the model and conducted in a way to be sufficiently reproducible. The results provide customers with the information they need to select the most efficient model for their use. It is more representative of real world emissions than the new WLTP lab test. We hope other manufacturers take up the opportunity of apply the method to their own models in the future and this becomes the default approach for reporting fuel economy.


Ceyal's picture


What is the real benefit of installing a PEMS at the rear of a car if not used to measure and publish all pollutants on this RDE cycle (HC, CO, Nox, PM, PN) ?
Because fuel consumption is already done by automobile magazines and internet sites such as and , so interest of publishing real consumption (and CO2) is not that high.

On the contrary, only ADAC is publishing something about real emissions & pollutants.
That is why you need
- to publish values of all pollutants on this RDE cycle
- to compare similar diesel and petrol cars from the same manufacturer such as PSA 308 Bluehdi120 and PSA 308 Puretech130 so that general public may have a good view of real pollution.

Here are some examples which are very far from the general thinking about pollutants generated by Diesel, Petrol and Hybrid cars : ADAC gives the best possible note 50/50 to 308 BlueHDI120 and 44/50 for its equivalent Petrol counterpart 308 Puretech130.
Hybrid Lexus NX300H gets 40/50 to be compared with 42/50 of Espace DCI160.
Renault Twingo/Smart get between 33/50 (TCE90) and 37/50 (SCE 70) because of PM/PN, ADAC states. Just remember that PM/PN are not measured at all during homologation ... just because these cars use Indirect injection systems.

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About the author

Greg Archer's picture

Director, Clean Vehicles