A study on the CO 2 and NO x emissions performance of Euro 6 diesel vehicles under various chassis dynamometer and on-road conditions including latest regulatory provisions Georgios Triantafyllopoulos a , Athanasios Dimaratos a , Leonidas Ntziachristos a, ⁎, Yoann Bernard b , Jan Dornoff b , Zissis Samaras a a Mechanical Engineering Department, Aristotle University of Thessaloniki, Greece b International Council on Clean Transportation, Berlin, Germany HIGHLIGHTS • Euro 6b diesel cars emit 5–16× NO x in the real world than certification tests. • NO x reduction systems are NEDC opti- mized and their on-road operation is compromised. • 2–8× NO x increase in dynamic driving over RDE, compared to 1.4–1.8× for CO 2 • Not-to-exceed NO x limits may be con- sidered for operation outside RDE boundaries. GRAPHICAL ABSTRACT abstract article info Article history: Received 2 October 2018 Received in revised form 7 February 2019 Accepted 9 February 2019 Available online 11 February 2019 Editor: Pavlos Kassomenos The current study presents a detailed analysis of the gaseous emissions, focusing on CO 2 and NO x , of diesel vehi- cles under several operating conditions. An assessment is also made on the impact and effectiveness of the Real Driving Emissions (RDE) test, which is mandatory by the European Union (EU) type approval regulation for pas- senger cars since September 2017. The method followed comprises emissions measurement tests on three Euro 6 diesel vehicles, under laboratory and various on-road operation conditions. Chassis dynamometer tests in the laboratory showed that emissions over the current type approval test (World-wide harmonized Light-duty Test Procedure or WLTP), and over the former one (New European Driving Cycle or NEDC), poorly reflect real- world levels. However, the most demanding CADC testing comes closer to real drive emissions. Comparison of driving conditions on the chassis dynamometer over different driving cycles and on the road reveals that the emission performance substantially varies between different tests, even for apparently similar operation condi- tions. The NO x emissions reduction strategy of pre-RDE monitoring Euro 6 vehicles seems to be optimized for the NEDC driving conditions, which are not representative of the real-world driving conditions. The real-world emissions during normal driving conditions are effectively captured with the new RDE test, however driving the vehicle dynamically, at conditions outside the RDE regulation boundaries, results to disproportional high emissions. This is a significant shortcoming which might be critical for populations living on hilly areas or those close to specific micro-environments, such as highway entrance ramps, traffic lights, etc. © 2019 Elsevier B.V. All rights reserved. Keywords: RDE WLTP CO 2 NO x Driving style Road grade Science of the Total Environment 666 (2019) 337–346 ⁎ Corresponding author. E-mail address: leon@auth.gr (L. Ntziachristos). https://doi.org/10.1016/j.scitotenv.2019.02.144 0048-9697/© 2019 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv