The Difference Between Reported and Real-world CO₂ Emissions: How Much Improvement Can Be Expected by WLTP Introduction?*

The monitoring and reporting of carbon dioxide (CO₂) emissions of light duty vehicles in Europe and other major markets is based on the New European Driving Cycle and the accompanying test protocol. This procedure has been proven non-representative of real world vehicle operation, fuel consumption and CO₂ emissions leading to a gap between officially reported emissions and the ones experienced during real world operation. This gap is reported to be increasing with time. To address this issue and improve the certification procedure for pollutant emissions of vehicles over real driving, the new Worldwide Harmonized Light duty vehicle Test Protocol (WLTP) was designed. This new test procedure is expected to provide more realistic emission and fuel consumption results. Scope of the paper is to estimate the extent of the certification-reality gap under the present conditions and, based on simulations, quantify the impact of the new test procedure. Tests were performed on three real vehicles over the two cycles which allowed the development of representative simulation models. A detailed simulation matrix was subsequently formulated, taking into account the limitations of the two tests and expected conditions occurring during real world driving. Results suggest that under present conditions the difference in certified and actually emitted CO₂ emissions for an average European passenger car reaches up to 25-35 g CO₂/km (~25% higher). WLTP introduction is expected to improve the picture however a shortfall in the order of 10-15% between official and real world is likely to remain.


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  • Accession Number: 01639627
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jun 28 2017 2:39PM