The WLTP uses a wider and more dynamic driving profile with consumption and emissions values that will better reflect real driving behaviour than the previous NEDC values. Despite there being no change in a vehicle’s real consumption, the stricter test cycle will generally result in higher measured consumption values.
Although the NEDC, too, guarantees cross-manufacturer comparability, it is now considered outdated. In spite of there still being inherent differences between measurements performed in the laboratory and those conducted on the road, the WLTP takes account of many more factors that have an effect on consumption.
Another reason for higher measured values is that, in future, optional extras will be included in the vehicle’s CO₂ value. The difference in the increase of the numerical CO₂ values between NEDC and WLTP may also differ for the same vehicle depending on technology and equipment specification.
The WLTP consumption and emissions cycle applies from September 2017 for newly certified vehicles and from September 2018 for all newly registered vehicles. The WLTP is mandatory for all EU member states; other countries will examine introducing the WLTP at a later date. From September 2017, the WLTP (Worldwide Harmonized Light-Duty Vehicles Test Procedure) will gradually replace the NEDC (New European Driving Cycle) and will provide greater transparency.
All vehicle classes (passenger cars) to be newly certified for emissions are tested under WLTP. At the same time, a NEDC consumption value will still be calculated for these vehicles and will continue in the near future to be shown as the legally required value in sales documents and all other publications.
For new models, there will also be a road test, the so-called Real Driving Emissions (RDE) test, which will verify that the Euro 6 limits for nitrogen oxides and particulate number are not exceeded after a conformity factor has been taken into consideration.
The entire vehicle portfolio will be certified under WLTP. The new WLTP values will be individually calculated for each vehicle and likely be included in sales documents and all other publications. The NEDC consumption will be shown for discontinued models.
Alongside the WLTP, an RDE road test will verify for all newly registered vehicles that they do not exceed the Euro 6 limits for the particulate number after a conformity factor has been taken into consideration.
For all newly registered vehicles, an RDE test will verify that they do not exceed the Euro 6 limits for nitrogen oxides after a conformity factor has been taken into consideration.
Until the end of 2020, both WLTP and NEDC values will be calculated for all vehicles. These values will be contained side by side in the vehicle papers with effect from the respective vehicle certification. From 2021, the WLTP values will be the only consumption/emissions values for all cars. Used vehicles will not be affected by this changeover and will keep their certified NEDC values provided they were first registered before 31 August 2017.
What is WLTP?
The abbreviation WLTP stands for Worldwide Harmonized Light-Duty Vehicle Test Procedure and is a test procedure that measures a vehicle’s consumption and emission values on a chassis dynamometer. From 1 September 2017, the WLTP will be gradually introduced and replaces the previous NEDC test procedure. Thanks to its dynamic bias, the WLTP is significantly more realistic in terms of actual driving behaviour.
The WLTP is characterised by significantly higher acceleration events as well as by a considerably more dynamic driving profile. The top speed is increased to 131 km/h, with the average speed rising to 47 km/h. The driving time is 10 minutes longer, along with a higher proportion of motorway journeys simulated on the dynamometer; at the same time, the proportion of stopping times is reduced. The driven distance is doubled to 23 kilometres. The shift points are calculated in advance and are specific to the vehicle and its powertrain.
All optional extras with an influence on vehicle aerodynamics, rolling resistance and vehicle mass will in future be included in the measurement. The power consumption of comfort/convenience functions will likewise lead to a higher CO2 value. The only exception in the first stage of the WLTP is the air conditioner.
With the WLTP, the goal is to introduce a globally binding standard, with EU countries taking the lead. This will help to compare the fuel consumption and pollutant emissions of vehicles from different manufacturers. In addition, the standards will help to enable authorities to verify compliance with the statutory emissions limits, from hydrocarbons (HC) to carbon monoxide (CO) and nitrogen oxides (NOx) to particulates.
What is WLTC?
The driving cycles of the WLTP are known as WLTC – Worldwide Harmonized Light-Duty Vehicles Test Cycle. For different vehicle classes, the WLTP has three different driving cycles that take the particular power/weight ratio into consideration. The majority of cars registered in the EU will be assigned to WLTC Class 3, which covers a power/weight ratio of more than 34 kW/t (46 PS/t). The test cycle for Class 3 vehicles consists of four parts – Low, Medium, High, Extra High. These simulate urban and extra-urban driving as well as driving on highways and motorways.
What is NEDC?
The NEDC (New European Driving Cycle) is the currently valid test cycle for cars. The first European driving cycle came into effect in 1970 with the goal of providing customers with comparable and reproducible values across all manufacturers. In 1992, the NEDC was extended beyond urban traffic.
At 34 km/h, the average speed in the NEDC is low, as are the acceleration events and maximum speed of 120 km/h. The composition of the cycle is no longer consistent with today’s average distribution of distances driven on different types of roads. The measurement takes account of neither aerodynamics and weight nor the energy consumption of optional extras and comfort/convenience functions, such as air conditioner, radio and seat heating. Added to this are technological parameters that promote discrepancies. For instance, start/stop technology has a relatively high influence in the NEDC, as the NEDC has a high proportion of stopping times.
In the case of vehicles with manual transmission, vehicle-specific parameters are not taken into consideration when the shift points are calculated. This can lead to significant discrepancies in consumption in comparison with real driving conditions.
Continuous technological advances mean that the NEDC is no longer up to date.
What is RDE?
RDE stands for Real Driving Emissions and is a road test for determining pollutant emissions. It describes a vehicle’s emissions under real on-road conditions. To date, exhaust emissions measurements for type approval have taken place exclusively on dynamometers. With effect from March 2016, within defined limits, emissions must also be measured under real driving conditions.
A PEMS (Portable Emissions Measurement System) is used to measure nitrogen oxide (NOx) and carbon monoxide (CO) emissions. At a later date, particulate emissions will also be measured. There is no set cycle; driving and measuring take place in real everyday traffic in compliance with the rules of the road. The vehicles are driven on public roads for between 90 and 120 minutes, one third each on urban and extra-urban roads and on the motorway. An average speed of between 15 and 30 km/h is specified for city driving, while the speed on motorways is 90 and at least 110, but not higher than 145 km/h. The outside temperature must be between 0 and 30 °C, with the air conditioner on. The road test must not take place at over 700 metres above sea level and can have an altitude difference of only 100 metres.
From September 2017, the Euro 6 emissions limits must be complied with in RDE road tests. In the first stage, this applies from 1 September 2017 for newly certified models and from no later than 1 September 2019 for all models.
Further information is available at the following sites:
German Association of the Automotive Industry (VDA)
