The current NEDC test regime which provides the official emission and fuel consumption figures has been around since the 70's and manufacturers have become familiar with it. The gap between official fuel consumption and test figures has widened, though not necessarily in a consistent way between makes and models.

The new World harmonised Light vehicle Test Procedure has been designed to counter many of the criticisms of the NEDC test and will certainly bring in more thorough testing and greater consistency of results. Better comparability is to be welcomed but in most cases tested CO2 will rise and mpg fall to more closely reflect real life fuel consumption.

Higher CO2 figures, estimated at between 4 and 20% more, will  hit company car drivers, if nothing else changes, since the appropriate percentage used to calculate BIK is based on the tested figure. Cars registered under NEDC testing will keep their lower tested CO2 figure but a similar car registered once WLTP comes into force could show a higher CO2 figure and be taxed several bands higher.

The legislation is detailed in : Commission Regulation (EU) 2017/1151 of 1 June 2017 which came into force in July and does not give the industry and national regulators much time to prepare. 

"In order to allow approval authorities and manufacturers to put in place the necessary procedures to comply with the requirements of this should apply to new type-approvals from 1 September 2017 in the case of categories M1, M2 and category N1 class I vehicles and from 1 September 2018 in the case of N1 vehicles of class II and class III and category N2 vehicles, and to new vehicles from 1 September 2018 in the case of categories M1, M2 and category N1 class 1 vehicles, and from 1 September 2019 in the case of N1 vehicles of class II and III and category N2 vehicles."

Most of the upcoming car launches in the next 10 months or so will have already been tested under the NEDC regime, so we may not see WLTP figures for a while. However there will be an overnight switch of test figures on 31st August 2018 when we will wake up to official emission and fuel consumption figures that are, in some cases, significantly worse on newly registered cars. 


Possible confusions:

  1. Can the same car have two sets of figures ? Cars registered after 1st September 2018 will have WLTP figures, as would a new type approval model that was tested after 1.9.17 and sold before 1.9.18. Confusion may arise as a result of all older types of cars (previously NEDC tested) having to be tested under WLTP in preparation for sale after 1.9.18. but the advance WLTP figures should be either hidden or just used for information until coming into force.
  2. The same vehicle may have a different CO2 figure if registered before or after the 1st September 2018. So company car drivers looking for delivery of a new car in October 2018 should press for registration in September if possible.
  3. We don't know what the difference on fuel consumption and emissions will be as the test regulations have only just been published. Tests under draft regulations show varying impacts according to the weight of the car, and engine technologies used.
  4. The new type-approval switch over date to WLTP on 1.9.17 won't have an impact until much later, due to new models being tested a long time before going on sale in the UK. And OEMs can keep testing under NEDC until 31st August 2017.
  5. There have been suggestions that NEDC or NEDC equivalent figures will be used for the purposes of calculating company car tax and VED, as well as fuel consumption figures, right up until January 2019. This was given strength by an  EU Commission Recommendation of 31.5.207 C(2017) 3525 final . 
  6. NEDC equivalent figures will still have to be calculated each year in order to measure manufacturers' compliance against EU average emission targets of 130gms CO2 per km in 2015 declining to 95 grams in 2021 as these targets were set for NEDC figures. However our reading of Regulations 2017/1152 and 2017/1153 is that NEDC equivalent CO2 figures can only be used for fleet averaging, and they were originally not intended for use on consumer cars. The approved calculation method CO2MPAS would not be able to  deal with electric/hybrids. 
  7. In December 2016 a HM treasury spokesman suggested that company car taxation could remain based on NEDC equivalent figures up to 2020. However there is no legislation yet in place to make this happen. The government could try and flesh out the correlation process used by the CO2MPAS programme to include electrics, hybrids and output fuel consumption  but some legislation is probably still required and we would then have two sets of figures. So that scenario would be very messy. UPDATE: HM Treasury have indicated that NEDC figures will continue to be used for tax purposes until April 2019, and there will be a review of CO2 thresholds for beyond then in the November 2017 budget.
  8. Or the UK government may produce a new set of company car tax appropriate percentages with lower thresholds for cars that have been tested under WLTP ? This could help fulfill an EU recommendation that WLTP should not raise taxation levels. But until we have a good idea of the impact of NEDC versus WLTP it will be hard to judge the reduction in thresholds required. European manufacturers under ACEA (Article of 27/7/2017) have called on governments to adjust the levels of CO2 based taxation for WLTP tested vehicles but so far without success. UPDATE: This is likely for April 2019 once the government has an idea of the impact of WLTP and can design revenue-neutral thresholds. Perhaps we shall see separate tables for NEDC and WLTP figures.

Update March 2018

The latest Finance Act includes the phrase that WLTP numbers can  "be ignored" until April 2020 so we now have some clarity. Cars bought after then will only have WLTP figures but HMRC is yet to consider how these will be taxed.

Meanwhile new cars are being tested under WLTP but the manufacturers won't let us see the figures yet. Anyone researching a new  car will see that CO2 figures are rising already for two reasons. Manufacturers can convert WLTP figures back to NEDC equivalent using the CO2mpas tool, but won't want to be seen to be too aggressive. And they are adding extra technology to reduce NOs, but which increases C02.