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How Is WLTP Different From NEDC?

In September 2018 the Worldwide Harmonised Light Vehicle Test Procedure (WLTP) was introduced as a new, and potentially more accurate, way to test new cars for their emissions and fuel economy. The procedure is much more stringent than the system it replaced, the New European Driving Cycle (NEDC), a lab-based testing system which often produced inflated fuel economy figures and incorrect emission results.

Diesel pollution testsOne immediate effect is that many new cars on sale are now advertised with lower fuel economy figures, but that is merely a reflection of the tougher, real world testing that the WLTP uses and doesn’t suggest that the cars have suddenly begun to perform worse than before. Indeed, the old NEDC system was discovered to provide incorrect data for both fuel economy and of course emissions, unearthed when Volkswagen’s “Dieselgate” scandal hit the headlines – the manufacturer had been using a cheat device during testing, leading to significantly higher emissions when the vehicles were then sent out onto the open roads. Moreover, the NEDC wasn’t an accurate reflection of newer technologies either, and hence the need for a new standard.

WLTP has not yet been introduced worldwide, with early adopters mainly in the EU and other European nations. Major manufacturing countries such as India, Japan and South Korea are expected to follow suit and use WLTP, or a very similar system, by 2021.

One thing to bear in mind when searching for new and used cars is that the old NEDC economy figures may still be used in advertising, so it’s important when comparing vehicles on this basis to make sure you’re looking at figures derived from the same testing, and also understand that WLTP figures will almost certainly be lower than NEDC numbers. All new cars must now be tested under WLTP except for a limited amount of stock which must be sold by September 2019 at the latest.

So how are the WLTP tests different?

Crucially, WLTP aims to reproduce real-world driving and test cars in different configurations, such as a range of weight specifications and on longer road tests at higher speeds. Some economy results will be presented with an associated speed range to enable purchasers to see what they can expect their vehicle to achieve. In the old tests, one vehicle was chosen to represent an entire range, which clearly could be selected to produce the most favourable results! Testing of hybrids is also now done at different stages of a battery’s lifetime and with multiple testing cycles. Again, this is to provide a more accurate indication of battery life, range and economy.

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In addition, a new emissions test, the Real Driving Emissions (RDE) procedure, assesses a car’s output in a genuine driving environment. This is mainly used to ensure that manufacturers don’t breach any relevant guidelines or legislation on emissions. While such tests won’t have any impact on your insurance policy premiums, there may be a longer-term effect on tax banding. New or amended categories are likely to appear when the NEDC tests become obsolete in 2020.

The WLTP tests are intended both to provide consumers with better data when researching a purchase and also to restore some confidence in a motor trade that’s struggling in the wake of the emission scandal and a downturn in worldwide sales.