What is WLTP and why does it matter?

WLTP stands for the Worldwide Harmonised Light Vehicle Testing Procedure. It is a global standard for testing the fuel economy and emission levels of vehicles. It was introduced in 2017 and extended to all cars and vans from September 2019.

Why was it introduced?

Since the early 1990s a New European Driving Cycle (NEDC) test was used to test fuel economy and emissions. The NEDC test was fully undertaken in a laboratory and did not reflect ‘real world’ driving e.g. driving on various types of road. As vehicle technology became more advanced NEDC struggled to keep up and the levels recorded were deemed inaccurate. The figures generated by the NEDC were not accurate. They typically underestimated emissions and overestimated fuel economy levels.

Scientists were puzzled about why air quality was not improving as much as it should be. NEDC was blamed for the discrepancy. The emissions scandal in 2017 focused the world’s attention on NEDC and this paved the way for WLTP.

Why does it matter?

Vehicle Excise Duty (VED) or road tax is based on the level of carbon emissions a vehicle emits and this is determined by WLTP. In a Total Car Check report we provide a fuel economy table showing the emissions and fuel economy of vehicles. This directly relates to the VED that will be payable.

Fuel economy label for used cars showing carbon emission rating
Fuel economy label for used cars registered after 1 April 2017

WLTP is a shift in the way of doing things following the emissions scandal. Trust had been lost in the way emissions were recorded and a new better system to promote confidence was needed. Accurately measuring carbon emissions of vehicles is also important so we can understand the impact they have on the environment.

How does the WLTP test work?

WLTP is carried out by both testing in a laboratory (30 minute test) and undertaking a 2 hour / 50 mile road test. Both tests are extensive, covering a range of standardised driving scenarios and parameters. A separate process is undertaken for electric and plug-in hybrid electric vehicles to determine emissions and fuel economy at varying levels of battery charge. The NEDC test of old was solely carried out in a laboratory and covered less scenarios – taking only 20 minutes to complete.

Why cars may have two carbon emission levels recorded?

Cars registered before 2017 would have had their CO2 levels measured using the old NEDC system. But some vehicles certified under WLTP between 2017 and 2018 have official paperwork showing both the NEDC and WLTP carbon emission levels recorded. This is because the ‘Certificate of Conformity’ under WLTP required both values to be disclosed for those vehicles certified during the transition period. For VED purposes the WLTP rating would be used to determine the VED band / payment due.

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