You may have already heard about the new emissions testing that is being introduced in the motor industry. This is as a result of new regulations regarding the way that fuel consumption and vehicle emissions are tested. It is called Worldwide Harmonised Light Vehicle Test Procedure or WLTP for short.  WLTP – A better way of testing.

The WLTP testing method gives a more realistic set of figures for emissions and fuel consumption that the old NEDC – closer to what you could achieve in everyday driving, even though they still take place in the laboratory.

But just how much do you NEED to know about WLTP?

It is very likely that the results of WLTP will become an important part of the decision process and help you compare and select the best car for your style of driving. It will also determine how much road tax is payable, and company car tax (benefit in kind), as both will still be linked to CO2 emissions.

So here are the key facts :

• WLTP regulations have been applied to cars from September 2017 including Hybrids
• WLTP regulations will be applied to light commercial vehicles from September 2019
• New testing figures are nearer to real world conditions – so there is more accuracy
• WLTP testing also takes into account additional extras added to the standard spec so it is much more realistic
• Fuel consumption figures may go down as the tests are more akin to real life conditions
• Some official C02 figures may increase with the new testing
• Higher official C02 could result in higher road tax in some cases
• Company car drivers may pay more Benefit in Kind Tax as a result if the official C02 increases
• Until 2020 new cars will be tested under both the new WLTP and the old NEDC systems and we will have both readings
• The EXISTING NEDC ratings for C02 will be used to calculate both Road Tax (VED) and benefit in kind (BIK) company car tax until 2020

Want to know more? Read on ….

The Worldwide Harmonised Light Vehicle Test Procedure (WLTP) – it is a bit of a mouthful!

WLTP testing replaces the NEDC tests carried out up until now. The NEDC system was first introduced in the 1980’s and although it was updated in 1997 has not kept up with the way cars have moved on in recent years.

From September 2018 all passenger carrying vehicles on sale must have type approval under the new WLTP legislation. In future all the official C02 emissions and fuel consumption figures will be based on the new test and may not be exactly the same as the current NEDC figures. The new tests are aimed at making car manufacturers more accountable for the data they produce on new cars while giving customers more accurate picture of how their car will perform in the real world in terms of miles per gallon (mpg) and carbon dioxide emissions (C02)

There is bound to be some confusion during the transition and some vehicles may show 2 different C02 emissions (one from the old system NEDC and the new WLTP figure)
More information can be found here:

In spite of its greater rigour WLTP is still a laboratory test, and so the new procedure supplements lab rigs with additional real-world testing, with some of the economy tests actually undertaken on the open road.


Figures apply to PHEV’s and electric cars too, so be prepared to see lower official range figures quoted for these.

WLTP will mean a completely new way of testing PHEV’s – cars that can fall furthest away from official figures, depending on how often you visit a plug. Plug-in hybrids will have to do the test until the battery is empty. Another assessment will be carried out with a completely flat battery to give a much more accurate idea of the economy real drivers can expect.


This is a European wide standard, including Europe and the UK so regardless of what happens with Brexit the EU has ordered that all car manufacturers must dramatically reduce emissions so that by 2021 CO2 must be limited to an average of 95g/km or they stand to face hefty fines.


There is a genuine need to improve air quality and to achieve that we must be working with accurate & realistic information. Car manufacturers have become very good at working the current system – we all remember the row over “Dieselgate”. Ultimately car buyers will get a much better idea of what the real economy and emissions levels of a new car should be under WLTP than the old NEDC tests – and that has to be a good thing.


Sorry – yet another acronym! This stands for Real Driving Emissions.

Briefly for the first time new models being developed for sale in the UK & Europe now have to undergo real on the road testing and the tail pipe emissions are measured while the car is driven in a range of every day and extreme conditions. This includes up a steep hill, carrying a heavy load, at high speed and low temperatures. This uses special portable equipment to measure the CO2 and NO ( Nitrogen oxide ) and particulates while the car is actually driving on the road to demonstrate that the new cars emissions ratings can be achieved in real world conditions and not just in the lab.


Most cars tested under WLTP and RDE are likely to show poorer fuel economy figures and higher C02 than the same car tested under the old NEDC system, and some significant increases have been found. For example a Peugeot 308 1.2 130 HP petrol engine saw its rating rise from 104g/km (NEDC) to 117g/km (WLTP) an increase of 13% and this kind of result is commonplace.
WLTP will apply to all new cars sold in the UK from September 2018, and by September 2019 all cars must have undergone the full RDE testing for both NO & particulate4 emissions. Without this certification the cars cannot be sold in the UK.


Not quite. There will be a transition period while the new standards are phased in and until 2020 new cars will be tested under both the new WLTP and the old NEDC systems. The EXISTING NEDC ratings for C02 will be used to calculate both Road Tax (VED) and benefit in kind (BIK) company car tax until 2020.

So hopefully in 2020 when the old NEDC ratings are finally phased out – there will not only be more clarity – but better air quality long term, which is what it is all about.

WLTP vs NEDC emissions testing

Image (c) SMMT


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