WLTP and RDE - New Tests for the Certification of Consumption

To be marketed, cars carry out a series of tests to ascertain their compliance with regulations. Tests to evaluate consumption, CO2 and pollutant emissions are performed in the laboratory and are based on specific driving cycles. In this way the tests are reproducible and the results comparable. This is important as only a laboratory test, which follows a standardized and repeatable procedure, allows consumers to compare different car models. On 1 September 2017 the new WLTP (Worldwide harmonized Light-duty vehicles Test Procedure) procedure came into force, which will gradually replace the NEDC (New European Driving Cycle) protocol.

 

The NEDC (New European Driving Cycle) has been the European driving cycle used to date for measuring fuel consumption and emissions from passenger cars and light commercial vehicles. The first European driving cycle had entered into force in 1970 and referred to an urban route. In 1992 it was also considered an extra-urban phase and since 1997 it has also been used to measure consumption and CO2 emissions. However, the composition of this cycle is no longer consistent with current driving styles and with the distances traveled on the different types of roads. The average speed of the NEDC is low (34 km/h), the accelerations are contained and the maximum speed is only 120 km/h.

WLTP uses new driving cycles (WLTC, i.e. Worldwide harmonized Light-duty vehicles Test Cycles) to measure the fuel consumption, CO2 emissions and polluting emissions of passenger cars and light commercial vehicles. The new protocol aims to provide customers with more realistic data, better reflecting the daily use of the vehicle.

The new WLTP procedure is characterized by a more dynamic driving profile and with more significant accelerations. The maximum speed increases from 120 to 131.3 km/h, the average speed is 46.5 km/h and the overall duration of the cycle is 30 minutes, 10 minutes more than the previous NEDC. The distance traveled doubles from 11 to 23.25 kilometers. The WLTP test consists of four parts according to the maximum speed: Low or Low (up to 56.5 km h), Medium or Medium (up to 76.6 km/h), High or High (up to 97, 4 km/h), Extra-high or Extra-high (up to 131.3 km/h). These parts of the cycle simulate urban and suburban driving and driving on extra-urban roads and highways. The procedure also takes into account all the optional contents that influence the aerodynamics, rolling resistance and mass of the vehicle, determining a CO2 value that reflects the characteristics of the individual vehicle.

 

 

NEDC

WLTP

Cycle time

20 minutes

30 minutes

Distance traveled

11 km

23,25 km

Full speed

120 km/h

131,3 km/h

Average speed

34 km/h

46,5 km/h

Driving stages

2 Phases

4 More dynamic stages

Influence of optional equipment

Not Applicable

Additional features are considered (which may differ from vehicle to vehicle)

Change gear

Gear change points defined

Different gear shifting points for each vehicle

Stop time

24%

12,5%

The WLTP procedure will gradually replace the NEDC procedure. The WLTP applies to new passenger car models homologated from 1st September 2017 and to all cars registered from 1st September 2018 and is mandatory for all EU member states. Until the end of 2020, both the WLTP and NEDC consumption and CO2 emission values will be present in the vehicle documents. The NEDC values will in fact be used to assess the average emissions of cars registered in the EU up to 2020. In addition, some countries may continue to use this data for vehicle taxation purposes. From 2021, WLTP data will be the only CO2 consumption / emissions values for all cars. Used vehicles will not be affected by this step and will retain their NEDC certified values.

The new WLTP test procedure is more representative of the current driving conditions than the NEDC procedure, but cannot take into account all possible cases including the effect due to the driving style that is specific to each individual driver.
Therefore there will still be a difference between the emissions and consumption measured in the laboratory and those deriving from the use of the vehicle in the real world and the extent of this difference will depend on factors such as driving behavior, the use of on-board systems (e.g. air conditioning), traffic and weather conditions that are characteristic of each geographical area and each driver.
For this reason, only a standardized laboratory test allows to obtain values with which it is possible to compare different vehicles and models fairly.

RDE Test

The RDE test verifies that cars maintain low emissions even in real driving conditions on the road. The RDE test does not replace the WLTP laboratory test, but supplements it. During the RDE test, the car is driven on the road in a wide range of different conditions. Conditions include: different altitudes and temperatures, an additional payload, driving uphill and downhill, urban roads (low speed), rural roads (medium speed), highways (high speed).
To measure pollutant emissions while driving the vehicle on the road, the cars carrying out the test are equipped with portable measurement systems (PEMS) that provide complete real-time monitoring of the main pollutants emitted by the vehicle. PEMS are complex equipment that integrate advanced gas analyzers, exhaust mass flow meters, weather station, satellite geo-location and a network connection. The collected data are analyzed to verify that the conditions surrounding the RDE trip have been reached and that the emissions remain within the limits set by the regulation.

What changes for Customers?

The new WLTP procedure will provide a more realistic criterion for comparing the consumption and CO2 emissions values of the different vehicle models as it has been designed to more accurately reflect real driving behavior and to take into account the specific technical characteristics of the single model and version, including optional equipment.