Report finds WLTP hugely over-estimates car fuel economy

What went wrong? 

After Dieselgate, the EU moved to replace the standardised New European Driving Cycle (NEDC) laboratory fuel economy tests, which dated back to 1992, with a new economy test format. 

The Worldwide Harmonised Light Vehicles Test Procedure (WLTP) then arrived in 2017. The WLTP test cycle was longer (30 minutes instead of 20 minutes), conducted over a greater distance (14 miles instead of six miles), included less stopping, took in higher average speeds and required greater levels of acceleration. 

Assurances were given that the WLTP driving cycle “was based on a global statistical survey of real driving profiles”, but new in-car technology quietly deployed by the EU in new cars since 2021 has now proved the test to be significantly overestimating cars’ real-world economy.

It wasn’t widely discussed, but the EU legislated for the installation of on-board fuel consumption monitoring devices (OBFCMs) in vehicles sold in member states. 

These had to be fitted to cars registered from 2021 and in vans registered from 2022. The European Commission said: “Regulation EU 2019/631 also tasked the Commission with monitoring the ‘realworld’ CO2 emissions of vehicles on the road, using the data read out from the OBFCM devices and comparing it with the corresponding official WLTP data.” 

Now the first results of this real-world monitoring have thrown the EU’s fleet CO2 targets into doubt. 

What happens now? 

With the exception of its reaction to the real-world charging patterns for PHEVs (it will change the way their CO2 emissions are calculated next year), the Commission’s report was relatively mild in tone. 

It said the initial data wasn’t yet “broad or representative enough to draw firm conclusions” but did express concern about the predominance of heavy SUVs and luxury vehicles, which stray even further from the WLTP results than mainstream cars. 

However, a parallel report from the European Court of Auditors was harder-hitting. It admonished the European Commission and member states for not submitting realworld CO2 data in time, and wasn’t interested in simply refining current legislation for descending fleet CO2 targets. 

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