Worldwide Harmonized Light-Duty Vehicle Test Procedure: This test procedure determines a vehicle's consumption and emission values on a roller dynamometer. Since 1 September 2017, the WLTP has been rolled out gradually and replaced the previous NEDC test procedure. Thanks to its dynamic focus, the WLTP is significantly more realistic than the previous procedure. At the same time, many requirements, e.g. in relation to the determination of driving resistances or conducting dynamometer tests, have been made significantly stricter compared with the NEDC. Especially these modified parameters lead to a numerical increase of the CO₂ values, although the efficiency of the vehicles is not changed by the new measurement procedure.
The driving cycle of the WLTP is called WLTC – Worldwide Harmonized Light Vehicle Test Cycle. For different vehicle models, the WLTP has three different driving cycles, which take account of the respective power-to-weight ratio. Most cars registered in the EU, which have a power-to-weight ratio of more than 34 kW/t (46 PS/t), are assigned to WLTC Class 3. The test cycle for Class 3 vehicles is made up of four parts – low, medium, high, extra-high. These simulate urban, extra-urban and motorway driving.
Up until 2018, emission and consumption values in Europe have been determined according to the NEDC (New European Driving Cycle). The first European driving cycle was introduced in 1970 with the aim of providing customers with comparable and reproducible values across all manufacturers. In 1992, it was extended beyond urban driving. Since the inclusion of cold starting in 2000, the NEDC has not undergone any further fundamental change. Up until the end of 2020, NEDC values will continue to be determined in addition to the WLTP values to allow verification of compliance with fleet targets.
Real Driving Emissions: In connection with compliance with emissions limits with the application of conformity factors, it must be verified – for particulates from emissions phase Euro 6c according to WLTP or additionally for NOₓ from emissions phase Euro 6d-TEMP – that the Euro 6 limits are not exceeded in road tests within the legally valid parameters. In the past, emissions measurements for type approval were carried out exclusively on a dynamometer. With effect from March 2016, emissions must increasingly also be certified under real driving conditions within defined parameters. Since September 2017, for new emission types the Euro 6 limits for both nitrogen oxides NOₓ and particulate number PN must be met in RDE road tests subject to the application of conformity factors. Since 1 September 2019, this applies to all newly approved vehicles.
Field tests check whether “young” customer vehicles comply with WLTP specifications. Cars are selected that are between six months and five years old and have a mileage of 15,000 to 100,000 kilometres.
The European Union sets the emissions limits for motor vehicles in regulations. In the Euro 6d-TEMP emissions phase, an RDE test must confirm both the Euro 6 nitrogen oxide limits and the Euro 6 limits for the particle number taking into consideration legally defined conformity factors. In addition, as in the Euro 6c emissions phase, the Euro 6 limits, also measured in the lab, must be confirmed according to WLTP. Euro 6d-TEMP applies to new emission types since 1.9.2017 and to all newly approved vehicles since 1.9.2019. As of 2020, emissions must be determined according to the Euro 6d follow-up standard.