Characteristics of MOBILE4 and EMFAC7E Modelsby Julie Fieber, Systems Applications Int, San Rafael, United States,
Barbara Austin, Systems Applications Int, San Rafael, United States,
Jeremy Heiken, Systems Applications Int, San Rafael, United States,
Abstract: Several recent studies (e.g., Lawson et al., 1990; Ingalls, 1989) have indicated that the EPA and ARB vehicle emission factor models MOBILE4 and EMFAC7E underpredict in-use vehicle emission rates. Alternative theories have been advanced to explain why the models are unable to achieve more accurate predictions, and several areas of further study have been suggested. We conducted a comparative study of the models to determine their weaknesses due to either limited data or faulty assumptions and to assess the relative importance of these weaknesses. This paper summarizes the key findings of the study.
Subject Headings: Model analysis | Comparative studies | Mathematical models | Emissions | Vehicles | Model accuracy | Data processing
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