RDE is short for real driving emissions and represents an on-road test to verify pollutant emissions. It describes vehicles' on-road emission response in real conditions. Exhaust gas measurement for the purposes of model series authorisations used to be performed at test stations only. Since March 2016, testing has also taken place in real world conditions to be more representative of customers’ everyday driving experiences.
A PEMS unit (portable emissions measurement system) is used to determine nitrogen oxide (NOx) and carbon monoxide emissions (CO). At a later point particulate emissions will also be determined. In this process, there is no defined cycle and test drives as well as measurements are carried out in real, everyday traffic situations in compliance with the highway code. Vehicles are driven on public roads for between 90 and 120 minutes, one third each in urban environments, extra-urban environments and on motorways.
In urban environments the intended average speed is between 15 km/h and 30 km/h, on motorways between 90 km/h and a minimum of 110 km/h, but no faster than 145 km/h. The ambient temperature must be between 0 and 30° and the air conditioning system must be on. Test drives must not be carried out at altitudes above 700 metres above sea level and they must feature a maximum of 100 metres difference in altitude.
From September 2017 Euro 6 emission limit values must be complied with during RDE cycles. In the first step this applies to models to be newly certified from 1 September 2017 and from 1 September 2019 at the latest for all models.