Nedc Wltp Comparison Essay

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.

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  • Supplemental Notes:
    • Alternate title: Comparison of Gaseous Emissions from Light-Duty Vehicles Under New European Driving Cycle and World-Wide Harmonized Light-Duty Test Procedures. This paper was sponsored by TRB committee ADC20 Transportation and Air Quality.
  • Corporate Authors:

    Transportation Research Board

    500 Fifth Street, NW
    Washington, DC  United States  20001
  • Authors:
    • Marotta, Alessandro
    • Pavlovic, Jelica
    • Serra, Simone
    • Anagnostopoulos, Konstantinos
    • Ciuffo, Biagio
    • Fontaras, Georgios
    • Tsiakmakis, Stefanos
    • Zacharof, Nikiforos
  • Conference:
  • Publication Date: 2015


Media Info

  • Media Type: Digital/other
  • Features: Figures; References; Tables;
  • Pagination: 13p
  • Monograph Title: TRB 94th Annual Meeting Compendium of Papers

Subject/Index Terms

Filing Info

  • Accession Number: 01555371
  • Record Type: Publication
  • Report/Paper Numbers: 15-4945
  • Files: TRIS, TRB, ATRI
  • Created Date: Dec 30 2014 1:39PM

The European Commission has been actively involved in the development of the World-wide harmonized Light duty Test Cycle (WLTC) and corresponding Test Procedure (WLTP), and is currently working to introduce them in the European type approval (TA) procedure. The present study analyzes and estimates the effects of the introduction of WLTP on the average CO2 emissions and average vehicle energy demands (VEDs) from different segments of the European vehicle market. Twenty gasoline and eleven diesel vehicles were tested on the current European TA procedure NEDC, and on the evolving WLTP. These WLTP tests were then used as base line to estimate for each vehicle a WLTP best case and a WLTP worst case scenario, in line with the finalized version of the WLTP. In the WLTP worst case scenario (WLTP-H) results showed CO2 emissions and energy demands to be on average 11% and 44% higher than NEDC, respectively. Best case scenario (WLTP-L) has on average 1% higher CO2 emissions and 26% higher energy requirements than the NEDC. These values should be considered on top of the 8% average difference between the JRC NEDC test results and the official type approval values. The higher vehicle inertia and road loads (RLs) along with the higher vehicle speeds, are the key parameters of the new procedure that contribute to the increased CO2 emissions and vehicle energy demand (VED). Results from the present study show that moving from NEDC to WLTP have a stronger impact on diesel than on gasoline vehicles. The highest effect of WLTP introduction is measured for vehicles that comply with EURO 6 emission standard (14% increase in CO2 emissions from NEDC to the simulated worst case WLTP), with also the largest difference between JRC measured NEDC tests and declared type approval values (11% difference).


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