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The Worldwide Harmonised Light Vehicle Test Procedure (WLTP)

The European Union has developed a new test, called the Worldwide Harmonised Light Vehicle Test Procedure (WLTP). This will replace the current NEDC test procedure for establishing the official Fuel Consumption and CO2 emissions of new cars.

The purpose of this note is to explain how WLTP will be presented within the VCA car fuel Data, CO2 and vehicle tax tools.

When does the new testing regime begin?

Manufacturers will be required to obtain approval under WLTP from 1 September 2017, with this becoming mandatory for all new cars by September 2018. Results from WLTP testing will start to appear on the VCA car fuel Data, CO2 and vehicle tax tools  towards the end of 2018.

What difference will it make?

The new testing regime aims to provide a closer representation of ‘real-world’ fuel consumption and CO2 figures and provide model specific values at the point of sale. It differs from the outgoing NEDC process in a number of ways although all tests will continue to be conducted in a laboratory allowing meaningful comparisons between cars to be made.

One of the obvious differences is the structure of the data resulting from the new test. For petrol / diesel cars for example, the terms used to describe test cycle driving phases: “urban”, “extra-urban” and “combined”, will no longer be used. In their place, the data will be expressed as “Low”, “Medium”, “High”, “Extra-high” and “Combined”.

During the transitionary period, i.e. prior to January 2019, there will be cars on the database that may have been tested under NEDC or WLTP. It is very difficult to compare two similar cars tested under different regimes, so to avoid confusion and to ensure like-for-like comparisons can be made, the initial search results will not show WLTP test results. Instead, where a car was tested under WLTP, the “NEDC equivalent” data, i.e. figures that would have been achieved had the car been tested under the outgoing NEDC standard, will be shown instead.

From 1st January 2019, the database will show WLTP results for Fuel Consumption. Results shown for CO2 emissions however, will continue to be NEDC or NEDC equivalent figures until 6th April 2020 (see  Statutory Instrument 2018 No. 673 - ROAD TRAFFIC ENVIRONMENTAL PROTECTION The Road Vehicles (Defeat Devices, Fuel Economy and Type- Approval) (Amendment) Regulations 2018).  

How will the implementation of WLTP affect car tax?

The CO2 emissions figure is used to determine the cost of Vehicle Excise Duty (‘car tax’) for new cars during their first year of registration. For those cars 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. From the 6th April 2020, the CO2 value obtained under WLTP will be used instead of the NEDC equivalent. When WLTP does start to be used to calculate vehicle tax, it will only affect cars that at that time are unregistered, i.e. the CO2 figure that is used for tax purposes when the car is first registered will not change during its lifetime.

For more information on current car tax rates, please visit

Further information

You can read more about WLTP in a number of places on-line. These include sites published by the European Automobile Manufacturers Association (ACEA) :; and The Low Carbon Vehicle Partnership (LowCVP)

Further information on WLTP will also be made available on the GOV.UK website in due course.

Important notes

It should be noted that fuel consumption figures quoted under NEDC or WLTP are obtained under specific test conditions. While WLTP is a closer representation of the figures you are likely to achieve in the real-world, there are many variations in driving styles; vehicle accessories and additional weight carried that will affect fuel consumption that you actually achieve. The figures do however, serve as a means of comparing models of a similar type.

Whilst every effort is made to ensure that the data provided is accurate, the Vehicle Certification Agency cannot accept liability for any inaccuracies. Visitors who rely on the information do so at their own risk. Further terms and conditions can be found here: /fcb/fuel-consumption-and-co2-tools-disclaimer.asp

Please note that VCA has no control over the content or accuracy of other websites, nor should it be inferred that endorsement of any third-party web-sites listed here or elsewhere applies.