From NEDC to WLTP
More realistic consumption and emission values through more realistic test conditions
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What is WLTP all about?
The “Worldwide Harmonised Light Vehicle Test Procedure” or WLTP was a protocol introduced ot measure vehicles’ fuel consumption, CO2 and pollutant emissions. The procedure was developed by the United Nations Economic Commission for Europe (UNECE) to replace the current “New European Driving Cycle” (NEDC), which had been in use since the 1990s.
One of the main objectives of the WLTP procedure is to better align the laboratory test results with realistic vehicle usage, based on current engine technologies. Given the importance of CO2 targets for the economic performance of vehicle manufacturers worldwide, WLTP also aims to harmonise test procedures on a global level, in order to create an equal playing field in the market.
WLTP in detail
The CO2 measurements resulting from the WLTP tests are included in the vehicle’s Certificate of Conformity and will be used to audit manufacturers’ compliance with the CO2 targets set by the European Union. In many countries, the new CO2 test results are now taken into consideration and used for the taxation of car registration and ownership.
In addition to WLTP, the EU Commission introduced enforce Real Driving Emissions (RDE) as a supplementary type approval requirement for the EU6d Emission Regulation. Unlike NEDC and WLTP, the Real Driving Emissions tests measure pollutants such as NOx while vehicles are driven on the road, thereby serving to confirm if the results of the lab tests are also reflected under normal usage conditions. RDE testing will be performed on a representative set of vehicle models.
Until 2020, both the NEDC and WLTP standards were maintained, whereas NEDC remained the legally binding norm for CO2 target monitoring of manufacturers. The European Union had to review therefore need to review the CO2 targets for 2020-2021 based on WLTP emission results.
The WLTP procedure was implemented by all UNECE members (EU-28, Norway, Iceland, Switzerland/Liechtenstein, Turkey and Israel) according to the above timeline. Other countries that signed the WLTP agreement, such as China, Japan, South Korea, Russia, India and the USA, are currently in a monitoring position and have not yet communicated any implementation timeline.
As optional equipment may had an impact on the weight and aerodynamics of a vehicle, the WLTP test better reflected the expected emissions levels of individually built vehicles. The WLTP tests are lab-based, in order to ensure the comparability of test conditions for all vehicles, such as wind, temperature, traffic density, condition of the road. Results therefore represent average usage conditions, and individual driving behaviour may still differ strongly.
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WLTP Basics FAQ
WLTP is a legally binding certification requirement and applies equally to all manufacturers.
WLTP was introduced in the EU-28 countries as well as in Norway, Iceland, Switzerland (and Liechtenstein) and the EU user states Turkey and Israel.
In principle, the change to WLTP does not change the way vehicles are already approved. In the first step of the introduction from September 1st 2017, WLTP is initially relevant for new type approvals. The manufacturers must apply to the relevant competent authorities if they want to place a new vehicle on the market or if a model is subject to significant technical modifications. From September 1st 2018, the WLTP guidelines are then mandatory for all new registrations.
In many countries, car taxation is partly measured by the CO2 emissions of a vehicle. However, the extent to which the new test procedure affects this regulation has not yet been clarified to date (as of September 2017) and is still regulated by national law.
Optional extras can alter the weight or the aerodynamics of the vehicle and thus also affect fuel consumption and emissions. In the selection of special equipment during the configuration of a vehicle, it will therefore be recognisable in the future, how the CO2 value of the vehicle changes.
In reality, the consumption and CO2 emissions of a vehicle are dependent on a number of factors, which can not be reconstructed in the laboratory with WLTP 1: 1. A key factor here are the different driving styles. This means that if two drivers drive the exact same vehicle under the exact same conditions in real road traffic, different values will necessarily result, for example, by individual acceleration and braking behavior.