Majority of post-RDE Euro 6 cars still over-emitting, tests show

The testing found that light-duty diesel vehicles Euro 5 and pre-RDE Euro 6 still emit average NOx emissions 4 to 8 times higher than their respective emission standard limits, despite manufacturer software changes following the Dieselgate scandal.

The study also found that NOx emissions of diesel vehicles significantly improved, with an average 60 per cent reduction, following the introduction of the RDE Euro 6d-TEMP standard.

The majority of Euro 6 diesel cars manufactured after the Real Driving Emission test (post-RDE) are still over-emitting, despite significant improvements, warns a new report from the TRUE Initiative. The study, in partnership with Transport Scotland, analysed real-world nitrogen oxide (NOx), hydrocarbons (HC) and carbon monoxide (CO) vehicle emissions data, collected by remote sensing technology, in the cities of Edinburgh and Glasgow during October 2021.

The majority of vehicles tested were passenger cars and pre-RDE Euro 6 vehicles accounted for over 30 per cent of all measurements. The analysis identified that despite improvements, post-RDE Euro 6 cars showed variable NOx emissions performance across vehicle families, up to two and four times the laboratory and RDE type-approval limit respectively. Only a minority had mean real-world emissions below the RDE type-approval limit.