Getting to know the WLTP

The Worldwide Harmonised Light Vehicle Test Procedure (WLTP) has been making the headlines, and this week’s “Getting to Know” guide focuses on what it is and what it covers.


What is the WLTP?


The Worldwide Harmonised Light Vehicle Test Procedure (WLTP) is a process for establishing the official fuel consumption figures and CO2 emissions of new cars. It replaces the previous fuel economy testing procedure, known as the New European Driving Cycle (NEDC), which was unveiled back in 1992.


Why was the WLTP introduced?


The WLTP has been designed to enable motorists to have access to more accurate information and model specific values at the point of sale through using a closer representation of ‘real-world’ fuel consumption and CO2 figures.


When will the WLTP come into force? 


Since September 2017, all new models introduced to the market for the first time have been tested in line with the WLTP. However, all new car registrations from September 2018 will be evaluated according to the WLTP.


What are the main differences between the NEDC and the WLTP?


One of the principal differences is the how the data resulting from the new test will be presented. For petrol and diesel-fuelled cars, the familiar terms of “Urban”, “Extra-urban” and “Combined”, which have an associated mpg figure, will no longer be used. Instead, the information will be categorised as “Low”, “Medium”, “High”, “Extra-high” and “Combined”.


The new WLTP laboratory test will also be supplemented by an emissions test that measures pollutants directly on the road, otherwise known as RDE (Real Driving Emissions).


How will it work for plug-in hybrids and EVs?


WLTP figures will also apply to PHEVs and electric models. For plug-ins, the test will be repeated several times, starting with a full battery and repeating the evaluation until the battery is empty. An additional assessment will be carried out with a completely flat battery, to give a much more accurate idea of the economy drivers can expect. For electric vehicles, the official emissions and economy figures will be scaled according to the car’s range.


How will the WLTP affect car tax?


The CO2 emissions figure is used to determine the cost of Vehicle Excise Duty (otherwise known as road tax) for new cars during their first year of registration. For those approved under WLTP, a figure equivalent to what would have been achieved had the car been tested under NEDC will be used and displayed on the database.


At some point, it is expected that the CO2 value obtained under WLTP will be used instead of the NEDC equivalent, although exactly when this transition will be made is unclear. When WLTP does start to be used to calculate vehicle tax, it will only affect cars that at that time are unregistered. The CO2 figure that is used for tax purposes when the car is first registered will not change.


 Where can I find out more about WLTP?


For more information on the Worldwide Harmonised Light Vehicle Test Procedure (WLTP), visit


Image courtesy of Citroen UK