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September countdown for new fuel efficiency tests on vehicles

September countdown for new fuel efficiency tests on vehicles

(Posted on 03/05/18)

Europe’s car makers are busy preparing for the introduction of new tests which will determine vehicle fuel efficiency ratings.

The European Union has developed a new test, called the Worldwide Harmonised Light Vehicle Test Procedure or the simpler acronym - WLTP. This will replace the current NEDC test procedure for establishing the official fuel consumption and CO2 emissions of new cars.

Basically, it’s Europe’s fuel efficiency ratings for cars including diesel, petrol, electric and hybrids. The new tests will involve real-world testing rather than pure lab tests to determine efficiency and those behind the scheme claim the tests are the first to be completed in real driving conditions.

They will hopefully give buyers comprehensive and reliable mpg figures, helping them to compare and select the car best suited to the type of driving they do.

Commissioner Elżbieta Bieńkowska, responsible for Internal Market, Industry, Entrepreneurship and SMEs at the European Commission said: "A quick shift to zero emissions vehicles is in all our interest given the public health and environmental risks at stake. And it's crucial for the car industry if it wants to remain internationally competitive. But for the time being, diesel cars remain part of our lives and we must rebuild confidence in this technology. That is why having new and more reliable tests for new cars is essential. And for cars already on the road, Member States must do their job, enforce the law and take additional steps, together with all stakeholders, to bring down emissions of the existing fleet."

When does the new testing regime begin?

The first phase of testing was introduced in September 2017 and was applicable to all new cars but the tests will apply to all car registrations in the European Union from September this year.

Manufacturers were 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  as tests are completed and the data becomes available.

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 several 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 between September 2017 and September 2018, 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.

Where NEDC equivalent figures are used in this way, VCA will provide a link to a separate area of the site displaying the original WLTP test results for that car.

How will the implementation of WLTP affect car tax?

The CO2 emissions figure is used to determine the cost of car tax (vehicle excise duty) 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.

At some point, it is expected that the CO2 value obtained under WLTP will be used instead of the NEDC equivalent, although exactly when that will be is not known. 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 during its lifetime.

In some cases, the new tests may result in an increase to the CO2 figures for vehicles, compared to previous figures under the NEDC test. If the official CO2 figure increases, the Vehicle Excise Duty which applies to vehicles may also increase as a result. Where a vehicle is being supplied to a company car driver, their Benefit in Kind tax rate may also be affected.

For more information on WLTP visit or

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