The WLTP test procedure

The “Worldwide Harmonised Light Vehicles Test Procedure”, WLTP for short, replaces the outdated NEDC (“New European Driving Cycle”) procedure for determining consumption and emission values. However, a modern certification procedure should provide values that are as close to reality as possible, with the help of which you can compare different vehicle types. The NEDC procedure no longer meets this requirement. Due to this, the WLTP procedure was developed by an initiative of the United Nations Economic Commission for Europe (UNECE). The WLTP procedure is based on empirically collected real driving data from routes in Asia, Europe and the USA. In addition, the consumption values must be shown specifically for each vehicle. This means that mass, air and rolling resistance as well as optional equipment are taken into account when determining the certification values. This means that the WLTP test can accurately measure the difference from a vehicle to a vehicle with a CombiFuel system.


Real Driving Emissions (RDE)

In the new certification procedure, pollutant emissions are measured in real vehicle operation on the road. The determination of “Real Driving Emissions”, short RDE, is intended to ensure that pollutant limits for nitrogen oxides and the particle count are not only complied with under laboratory conditions during the WLTP test, but also in real road traffic. For this purpose, PEMS devices (Portable Emission Measurement System) are attached to the vehicle and thus the pollutant content in the exhaust gases is measured while driving. A so-called Conformity Factor (Conformity Factor, CF) indicates by how much higher the values measured in road traffic may be at maximum compared to the WLTP laboratory values. After a transitional phase, the values for nitrogen oxides and the number of particles in the Euro 6d emissions standard may still be 50 % higher than the values specified in the laboratory. This surcharge reflects the measurement tolerance of the portable measuring devices in RDE tests and is to be reviewed annually and reduced if necessary.