Cambridge Environmental Research Consultants (CERC)

Volkswagen - EMIT Can Account for Real-World Diesel Emissions


Analysis of measurements from the last decade throughout Europe have demonstrated that ambient NOx and NO2 concentrations are not decreasing in line with the published emission factors (Carslaw et al. 2011). On-road vehicle testing in the UK has highlighted that the problem is primarily related to NOx emissions from diesel cars remaining relatively static (Carslaw & Rhys-Tyler, 2013). So are we really surprised by the recent admission by Volkswagen that their diesel cars emit much lower rates of NOx in standard laboratory conditions than in real-world scenarios?

When modelling air quality in urban areas it is critical that the most accurate emissions estimates are used. Currently for some pollutants the most accurate emissions appear to be those derived from on-road emissions testing and other techniques such as analysing roadside particulate measurements to estimate non-exhaust PM10 and PM2.5 (Harrison et al. 2012). CERC has developed the EMIT toolkit to allow users to edit the standard factors for exhaust and non-exhaust emissions in line with the most up-to-date emissions estimates. EMIT also enables the user to quantify the contributions from particular road vehicles, such as diesel cars, to emissions and concentrations, when used with ADMS-Urban. The apportionment is fully user-defined; for example emissions can be apportioned by EURO class or vehicle size.

At the upcoming ADMS-Urban & Roads User Group Meeting in Manchester, CERC will present validation results from an ADMS-Urban modelling scenario where EMIT has been used to calculate NOx and PM emissions consistent with real-world measurements; agreement between modelled and observed concentrations is very good. If you would like to know more about features of EMIT and ADMS-Urban that may improve your modelling results, please contact CERC.

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