All vehicles in the EU are subject to emissions testing prior to being released for sale in the market. Currently, this is done through a lab test called the New European Driving Cycle (NEDC), however, this is being replaced by the Worldwide Harmonised Light-Duty Vehicles Test Procedure (WLTP). WLTP will also be supplemented by the Real Driving Emissions (RDE) test that measures pollutants directly on the road. The new test will ensure that lab measurements better reflect the on-road performance of the vehicle.
There will be a phased transition between WLTP and NEDC between September 2017 and 2020. During this time vehicles will have a derived NEDC CO2 value and consumption value, as well as the WLTP CO2 and consumption values in relation to type approval. WLTP testing legislation came into effect on 01 September. Further details can be found in the timeline section.