This section describes the different sources used to collect the data needed to calculate the Ecoscore. Both direct emissions during the driving phase and indirect emissions related to the fuel life cycle are needed. Two categories of vehicles are distinguished: new and old vehicles. When data are missing, several methods are used to cope with it.
These are exhaust emissions. A share of these emissions depend on engine technology and another on fuel type and consumption. These originate from European studies or can be derived from the composition of the fuel used. A third set of emissions originates from the official type approval tests a vehicle undergoes before entering the European market. On a regular basis, the DIV of the FPS Mobility provides VITO with registration data of new and second hand vehicles. This data set is enriched with type approval emission data by the Dutch 'Rijksdienst voor Wegverkeer' (RDW). RDW collects these emission data for all vehicle models available in Europe.
Since March 2014, not only new vehicles that have already been registered by DIV are included in the vehicle database, but also brand new cars. These are cars that can already be ordered but have not been registered yet. These data come from Inmotiv, an automotive data provider. For these specific group of cars, the Ecoscore provided is only an approximation (based on the fuel type and CO2 emissions) as not all data is available. Eventually, the actual Ecoscore is calculated once the vehicle is registered and emission data can be retrieved from RDW.
These are emissions associated with the production and distribution of the fuel. The amount of indirect emissions depends on the fuel type and fuel consumption of a vehicle: the more a vehicle consumes, the more fuel needs to be produced, the greater the emissions will be. These data are based on European studies, and the Belgian electricity mix.
Only very few type approval data are available from vehicles dating from before 2002. Therefore, we opted to work with assumptions for the pollutant emissions of such vehicles. For vehicles dating from before 1998, this is not only the case for pollutant emissions, but also for fuel consumption and corresponding CO2 emissions. Therefore, additional assumptions regarding fuel consumption and CO2 emissions are used for these vehicles.
Air pollutant exhaust emissions
When emission data for air pollutants are lacking, gaps are completed by using the values from the table below (expressed in g/km). Starting from Euro 1, they perfectly correspond with the limits of the Euro emission standards (see European measures). Beware, we make an exception for NOx in the case of diesel cars.
Table 3: Overview of the limits of the different Euro emission standards Notes: The first date applies to new vehicle models, the second date applies to all new vehicles.
Noise production
If the noise production is missing, we assume a default value of 74 dB (A) for all vehicles with a conventional internal combustion engine or conventional hybrid (no plug-in) drivetrain. We assume that plug-in hybrids and fully electric vehicles are generally quieter, and therefore we assume a default value of 68 dB (A) for these types of vehicles.
CO2 exhaust emissions
When CO2 emissions are lacking, we use default values from the table below (expressed in g/km). The values in this table are the result of average emissions of a representative set of vehicles.
Table 4: Default value of CO2 exhaust emissions
Based on the assigned CO2 emissions, fuel consumption and associated indirect emissions can then also be determined.
You should have a look at your certificate of conformity (CoC) of your car. For most cars built after 2002, this CoC contains all required data, which can then be used to calculate the Ecoscore yourself by using the calculation module. Pay attention to the required units of the data in the calculation module!
The Ecoscore uses direct emissions measured during the vehicles' type approval tests. During these tests, it is verified whether a vehicle meets all relevant technical requirements. Regarding emissions, this implies verifying whether the emissions are lower than what the Euro stage of the vehicle imposes (currently Euro 6). The Euro stage set maximum values for the emission of about 4 pollutants: CO, NOx, HC and particulate matter. If a car emits less than the emission limits, it may be sold on the European market. These tests are done in a standardized way in which each vehicle needs to cover a certain driving cycle (WLTP) on a dynamometer while emissions are being measured. As of 2017, and in response to the Dieselgate, the type approval tests are extended with real-world emission tests.
From NEDC to WLTP driving cycle and RDE test procedure
Since 2017, the Worldwide Harmonised Light Vehicles Test Procedure (WLTP) for all emissions, and the Real-Driving Emissions (RDE) test only for NOx and PN, are in force. The first one is a laboratory test on a chassis dynamometer, while the second is a driving test under real-world conditions.
As of 2017, WLTP replaced the New European Driving Cycle (NEDC) as the driving cycle of reference for the type approval procedure. The reason was the fact that the NEDC only poorly reflected actual driving conditions and behaviour. It was characterized by very slow accelerations, low dynamics, and a small proportion of high speeds. The cycle included only briefly driving above 100 km/h (Figure 1). Therefore, the gap between real-world emissions and the test results was significant. The WLTP created by UNECE (the United Nations Economic Commission for Europe) has been developed to be closer to real-world driving conditions and behaviour with a longer test duration and more dynamic test cycles that differ depending on the vehicles' category (The Association of European Vehicle Logistics, 2019). The categories are based on the power-to-mass ratio and divided into 4. Figure 1 shows the driving cycle for the category 3b (PMR>34 W/kg). The procedure is also adapted for PHEV and BEV vehicles. Figure 1: NEDC and WLTP test procedure's driving cycle Source: Hooftman (2018)
Despite improved emissions measurements, a gap between laboratory and real-world emissions remains. It is expected to be 31% higher by 2030 (Hooftman, 2018). Therefore, as of 2017, the RDE test has been adopted as a complementary procedure to test NOx and PN emissions under real driving conditions (Regulation 2017/1151 EU).
The implementation of the tests for type-approval vehicles and EU targets has been carried out gradually. The process is summarized in Figure 2. Given the NEDC consideration for EU targets until 2021, a correlation procedure was implemented to ensure the transition towards WLTP tests. The CO2mpas tool allowed translating the CO2 WLTP values obtained during the tests into NEDC values. Since 2021, targets for car manufacturers are based on WLTP measurements and therefore the correlation procedure stopped (European Commission, 2021). In that context, the same rule apply to the ecoscore calculation when using direct emissions data.
As of 01/01/2021, the WLTP values will be used to calculate the Ecoscore of new cars, and no longer the NEDC2.0
Figure 2: Overview of the transition from NEDC to WLTP, accompanied by the CO2 emissions targets up until 2021 Source: Hooftman (2018)
Hooftman, N. (2018)., THE ROAD TOWARDS A ZERO-CARBON TRANSPORTATION SYSTEM BY 2050 THE ROAD TOWARDS A ZERO-CARBON TRANSPORTATION SYSTEM BY 2050 A comprehensive study for Belgium in a European context.
The Association of European Vehicle Logistics (2019), WLTP, RDE and automotive emissions targets.
European Commission (2021), IMPLEMENTATION AND PHASE-OUT OF THE NEDC/WLTP CORRELATION PROCEDURES FOR CARS AND LIGHT COMMERCIAL VEHICLES – Commission Note
Real-driving emission measurements
While the persisting gap between real-world emissions and laboratory measurements was already known, in 2015, the " dieselgate " scandal showed the need for an updated homologation tests procedure. It spotlighted the failure of diesel passenger cars to meet the NOx emissions limit target. Those excesses were proven to be deliberate. It triggered the revelation of other emissions fraud scandals, proving that most diesel passenger cars since 2010 exceeded the NOx emissions limit.
Since 2017, besides the implementation of the WLTP driving cycle experiments, an additional test called RDE test came into force. It consists of a real-driving conditions test that measures NOx and PN emissions. A Portable Emissions Measuring System (PEMS) is attached to the car and collects exhaust emissions data while driving under several traffic conditions. The road must be composed of urban, rural and motorway. The RDE procedure has been established and refined in four steps:
RDE Package 1 (published March 2016): It provides the overall framework for the RDE test procedure for NOx emissions monitoring. It also means that no requirements for NOx emissions are set up for this round.
RDE Package 2 (April 2016): It officially enforces a Not-To-Exceed limit for NOx to be implemented gradually. It is based on conformity factors.
RDE Package 3 (June 2017): It provides the framework for the RDE test for PN and the corresponding conformity factors, a procedure including cold starts emissions and a test protocol for hybrid vehicles. Besides, it discusses the possibility for the manufacturer to notify on the Certificate of Conformity (CoC) if their NOx emissions are lower than the limit, NOx emissions data being confidential.
RDE Package 4 (November 2018): It provides the framework for a more robust RDE procedure evaluation, including in-service conformity testing and surveillance tests to ensure compliance over the vehicle's life cycle. Since September 2019, in-service conformity testing for all newly registered vehicles includes RDE procedure.
The timeline of the implementation of RDE Packages is summarised in Figure 3. Figure 3: Overview of the implementation timeline of RDE package Source: Hooftman (2018)
Reference and useful links:
Hooftman, N. (2018)., THE ROAD TOWARDS A ZERO-CARBON TRANSPORTATION SYSTEM BY 2050 THE ROAD TOWARDS A ZERO-CARBON TRANSPORTATION SYSTEM BY 2050 A comprehensive study for Belgium in a European context.
The Association of European Vehicle Logistics (2019), WLTP, RDE and automotive emissions targets.
Remote sensing campaign in Belgium
Remote sensing campaigns were carried out in the Bruxelles region and several places in Flanders. Such campaigns allow monitoring the vehicles' pollutants emissions under real driving conditions.
Flanders
Remote sensing campaigns in several locations in Flanders were implemented in 2019 over about 190 000 vehicles for about a month. The study allowed to assess the vehicles' performances (up until Euro 6d TEMP vehicles) under real-driving conditions, especially in motorways where this tool was applied for the first time. It also discussed the possibility and recommendations to use remote sensing to detect tampering and high-emitters as the campaign proved to be efficient in pinpointing vehicles with potential deficient or removed gas exhaust cleaning tools. While representing a few proportions of the vehicle fleet, such high-emitters were responsible for a significant part of the overall pollutant emissions.
Other main results concern NOx emissions. Figure 4 shows that for passenger cars, NOx emissions for diesel Euro6d TEMP PC have significantly decreased and are closer to the RDE type-approval limits of the time which was about 3.4 g/kg of fuel. However, it still exceeds the emissions standard, illustrating the RDE procedure's limitation to provide sufficient conditions close to real driving. Those emissions remain higher than gasoline cars, even if gasoline cars can emit higher than expected on motorways.
Figure 4: NOx emissions for diesel and petrol passenger cars per Euro class Source: Hooftman et al (2020)
Brussels Capital Region
To assess the compliance of Euro 6d cars with the type-approval RDE limits, remote sensing campaigns have been carried out in Bruxelles Region for about a month in 2020. In collaboration with ICCT (International Council on Clean Transportation), Bruxelles Environment measured exhaust emissions for about 130 000 vehicles using remote sensing. It is a method to identify abnormal pollutant emitters and mitigate tampering. The study also supported new regulations guidelines for implementing the Low Emission Zone in Brussels.
As in Flanders, the main aspect raised was the significant reduction of NOx emissions for Euro 6d TEMP and Euro 6d (i.e. once the RDE testing was compulsory) compared to Euro 4, 5 and 6 diesel vehicles (Figure 4). The latter performed 3 to 5 times higher than the regulatory limit. However, Figure 4 shows that about 17% of Euro 6d TEMP diesel cars still exceed the RDE type-approval limit. It could be explained by the difference between real-driving urban conditions and the urban condition in the RDE test, meaning that RDE procedure does not sufficiently represent real-world urban areas. Therefore the remote sensing campaign help to support the decision to ban Euro 4 and 5 diesel vehicles.
Figure 5: Mean distance-specific NOx emissions from passenger cars per vehicle fuel and per emissions standard for the Brussels campaign data and the overall TRUE initiative data Sources: Bernard et al. (2021)
Besides, the campaign also focused for three days on to particulate number measurements (PN). It proved that 5% of diesel vehicles with supposedly particulate filters reached an alarming PN concentration, meaning that the filter were either deficient or removed. It confirms the need for a PN test during technical inspection. This finding aligns with the Flanders campaign's assessment about the use of remote sensing as a tool to detect tampering.
Hooftman N., Ligterink N., Bhoraskar, A., (2020) Analysis of the 2019 Flemish remote sensing campaign. Commissioned by the Flemish Government - Flanders Environment Agency - Team Air quality policy
Bernard et al. (2021)., Evaluation of real-world vehicle emissions in Brussels – Brussels Environments -TRUE Initiative
WLTP measurements deviation for PHEV vehicles
A significant gap has been measured for PHEV between WLTP data and real-driving emissions. According to ICCT (2020), the differences in CO2 emissions are 2 to 5 times higher in real-world conditions. The same applies to the Utility Factor (UF), which represents the proportion of distance travelled with the electric motor. It seems to be about 50% lower under real driving conditions.
Plötz et al. (2020). REAL-WORLD USAGE OF PLUG-IN HYBRID ELECTRIC VEHICLES FUEL CONSUMPTION, ELECTRIC DRIVING, AND CO 2 EMISSIONS. www.theicct.orgcommunications@theicct.org
Deviations from Homologation tests in Ecoscore
In practice, no one drives precisely like the standard driving cycle because each driver has a different driving style. Therefore, it is more likely than not that the actual fuel consumption differs from the one mentioned in the vehicle's' CoC. However, a car with lower official fuel consumption usually consumes less than a car with higher official consumption. Ecoscore is used for comparison and therefore, it needs to be done in a standardized way, regardless of which driver will ultimately drive it. It is thus best to use homologation data. Nevertheless, some deviations can occur between some pollutant emissions from homologation and real-world emissions and are detailed below. In this case, the data in Ecoscore are adapted.
The case of NOx emissions
Unlike other emissions, there is a problem with type approval NOx emissions from diesel cars. Real world tests proved that all diesel cars emits more NOx emissions than they should according to their Euro stage. Consequently, using NOx type approval values for diesel cars will give a biased image since a recent diesel car will not emit less NOx than an old diesel car. That's why we've adopted a fixed NOx emission level (NOx = 0.63 g/km, like Euro 2) in the Ecoscore calculation for all diesel cars with emission standard Euro 0-5. This modification has been implemented on our website since the beginning of October 2012. The result is that since then, the Ecoscore for diesel cars has been significantly lower than before: from a couple of points for Euro 3 diesel to up to more than 10 points for Euro 5 diesel.
From September 2015, every new diesel car sold must meet Euro 6. Since March 2015, a similar adjustment for actual NOx emissions was applied to Euro 6 diesels. Although Euro 6 diesels perform on average (slightly) better than their predecessors (Euro 0-5), in terms of actual NOx emissions, this is still much worse than what is required by the Euro 6 stage (Franco et al., 2014). Since March 2015, the Ecoscore has been calculated with an approximate and fixed NOx emission factor of 0.50 g/km (versus 0.63 g/km for Euro 0-5 diesels).
On the other hand, no correction is needed for petrol cars, and the Ecoscore calculation method remains unchanged.
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