Abstract
Abstract Real world emissions of oxides of nitrogen (NO x ) often greatly exceed those achieved in the laboratory based type approval process. In this paper the real world emissions from a substantial sample of the latest Euro 6 diesel passenger cars are presented with a focus on NO x and primary NO 2 . Portable Emissions Measurement System (PEMS) data is analysed from 39 Euro 6 diesel passenger cars over a test route comprised of urban and motorway sections. The sample includes vehicles installed with exhaust gas recirculation (EGR), lean NO x traps (LNT), or selective catalytic reduction (SCR). The results show wide variability in NO x emissions from 1 to 22 times the type approval limit. The average NO x emission, 0.36 (sd. 0.36) g km −1 , is 4.5 times the Euro 6 limit. The average fraction primary NO 2 (fNO 2 ) is 44 (sd. 20) %. Higher emissions during the urban section of the route are attributed to an increased number of acceleration events. Comparisons between PEMS measurements and COPERT speed dependent emissions factors show PEMS measurements to be on average 1.6 times higher than COPERT estimates for NO x and 2.5 times for NO 2 . However, by removing the 5 most polluting vehicles average emissions were reduced considerably.
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