Post-Dieselgate: Evidence of NOx Emission Reductions Using On-Road Remote Sensing

Stuart K Grange; Naomi J Farren; Adam R Vaughan; Jack Davison; David C Carslaw

doi:10.1021/acs.estlett.0c00188

Post-Dieselgate: Evidence of NO_x Emission Reductions Using On-Road Remote Sensing

Environ Sci Technol Lett. 2020 Jun 9;7(6):382-387. doi: 10.1021/acs.estlett.0c00188. Epub 2020 Apr 27.

Authors

Stuart K Grange^{1

2}, Naomi J Farren², Adam R Vaughan², Jack Davison², David C Carslaw²

Affiliations

¹ Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, Switzerland.
² Wolfson Atmospheric Chemistry Laboratories, University of York, York YO10 5DD, United Kingdom.

Abstract

The Dieselgate scandal which broke in September 2015 demonstrated that vehicle manufacturers, such as the Volkswagen Group (VWG), engaged in software-based manipulation which led to vehicles passing laboratory-based emission testing limits but were far more polluting while being driven on roads. Using 23 000 on-road remote sensing measurements of light-duty Euro 5 diesel vehicles in the United Kingdom between 2012 and 2018, VWG vehicles with the "Dieselgate-affected" EA189 engine demonstrated anomalous NO_x emission behavior between the pre- and post-Dieselgate periods which was not observed in other vehicle makes or models. These anomalous changes can be explained by voluntary VWG hardware and software fixes which have led to improved NO_x emission control. The VGW 1.6 L vehicles, with a simple hardware fix and a software upgrade, resulted in a 36% reduction in NO_x, whereas the 2.0 L vehicles that required a software-only fix showed a 30% reduction in NO_x once controlled for ambient temperature effects. These results show that even minor changes or upgrades can considerably reduce NO_x emissions, which has implications for future emission control activities and local air quality.