WLTP: What is it and how will it affect me?

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SO, the NEDC is done and the WLTP is taking over. No idea what we're talking about? Join the club.

Forget the acronyms for a second because they are both essentially the same thing: A means of measuring the fuel economy and emissions of your car.

The New European Driving Cycle (NEDC) was introduced back in the 1980s but it has gradually become increasingly outdated. This is mainly because it was based on theoretical driving rather than how actual human beings behave behind the wheel. Hence why it has now been replaced with the Worldwide Harmonised Light Transport Test Procedure (WLTP).

Without boring you with extraneous detail, the WLTP test is split into four parts and tests new vehicles at a range of average speeds, in different driving environments (City traffic or motorway cruise), and under braking and acceleration. The new test even takes into account the effect of additional features such as air conditioning, and engine and gearbox configurations. In short, it's a much more detailed test, and because it's based on real-world driving the results will match much more closely with on-road performance.

The change was introduced in 2017, but to allow a transition period between the two test procedures it is only from September this year that every new car must have WLTP emissions values. Until then all new cars must show both the old and new test results - because choosing a new car isn't confusing enough already.

It's great news that the new test will be much more realistic. It should also help to alleviate concerns that some people have over the future of diesel - they're largely unfounded so feel free to choose a diesel if it's the best option for you - and prevent a repetition of the recent emissions scandals.

But it doesn't seem to be without its problems.

You will wake up one morning to find that the perfectly clean and economical car you drove yesterday is suddenly 20% less clean and economical. We all know it's exactly the same car, but that's the effect some industry voices are suggesting the more detailed new tests will introduce. The car won't have changed, just the standards by which it is measured.

It doesn't take an Einstein to realise that this has wider implications.

For a start all of those government CO2 targets are based on the figures from the old NEDC test. All of a sudden it's going to be around 20% harder for everyone to meet those targets. We can't say how the new test will affect this in the long term but we wouldn't be surprised to see an increase in clean air zones and the number of cars that will be charged to enter them.

It could also have an impact on the running costs of your car, and by association the choice you make for your next lease car. If road tax is tied to CO2 emissions and those emissions suddenly increase then your chosen car is likely to jump up a few tax brackets. For this new test process to really work it probably needs to be accompanied by a complete overhaul of the VED brackets to ensure the system is fair. Be honest though, can you see the Treasury turning down a 20% increase in tax income?

It also means that all those people who might choose a plug-in hybrid vehicle (PHEV) will find the CO2 emissions have risen to the point where there is no benefit to be gained. The whole idea of a PHEV is to reduce CO2 emissions, and lower benefit in kind taxation, but due to the more intensive nature of the testing that could be wiped out. To be clear, it won't make your PHEV any less fuel efficient and environmentally friendly except on paper. But it's the paper that decides how much road tax you pay, or how much BIK tax business users pay, and the paper may well say you should pay more.

It's very early days at the moment so we can't predict exactly how drivers will react to the changes. It's also difficult to know which side of the fence to come down on.

When you spend your hard-earned money on a new car you deserve to have figures that are robust and trustworthy to aid the decision. The same applied to legislators who should have access to scientifically rigorous data to help formulate environmental legislation that actually works. On the other hand it seems that increased running costs, rising prices, and options bundled into ‘packs' could be the price we all have to pay.

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