A Comparison of Gaseous Emissions from Light-Duty Vehicles under the NEDC and the WLTP test procedures

The World-wide harmonized Light duty Test Procedure (WLTP), recently issued as GTR15 by the United Nations Economic Commission for Europe (UNECE)-World Forum for the Harmonization of Vehicle Regulations (WP29), is designed to check the compliance of Light Duty Vehicles (LDVs) around the world with respect to legislated emission standards, and to establish the reference vehicle fuel consumption and CO₂ performance. In the course of the development of WLTP, from 2010 to 2014, the Joint Research Center (JRC) of the European Commission has tested several gasoline and diesel vehicles, on both the New European Driving Cycle (NEDC) and on the progressive versions of the WLTP. Emissions of CO₂, NOx, CO, and THC from twenty-one Euro 4-6 vehicles (twelve gasoline and nine diesel) are reported in this paper to provide a preliminary qualitative comparison of gaseous emissions from such vehicles on the two cycles/procedures. The results demonstrated minimal average differences between CO₂ emissions over the NEDC and WLTP. Measured THC emissions from most vehicles stayed below the legal emission limits and in general were lower under the WLTP compared to NEDC. NOx emissions from gasoline vehicles and CO emissions from diesel vehicles did not appear to be much impacted by the change from NEDC to WLTP. On the contrary, NOx emissions from diesel vehicles and CO emissions from low-powered gasoline vehicles were significantly higher over the more dynamic WLTP and in several cases exceeded the emission limits. Results from this study can be considered indicative of emission patterns and could be useful to both policy makers and vehicle manufacturers in developing future emission policy/technology strategies.