Development of a Comprehensive Modal Emissions Model

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In August 1995, the College of Engineering-Center for Environmental Research and Technology (CECERT)
at the University of California-Riverside along with researchers from the University of Michigan
and Lawrence Berkeley National Laboratory, began a four-year research project to develop a
Comprehensive Modal Emissions Model (CMEM), sponsored by the National Cooperative Highway
Research Program (NCHRP, Project 25-11). The overall objective of the research project was to develop
and verify a modal emissions model that accurately reflects Light-Duty Vehicle (LDV, i.e., cars and
small trucks) emissions produced as a function of the vehicle’s operating mode. The model is
comprehensive in the sense that it is able to predict emissions for a wide variety of LDVs in various
states of condition (e.g., properly functioning, deteriorated, malfunctioning). The model is now complete
and capable of predicting second-by-second tailpipe emissions and fuel consumption for a wide range of
vehicle/technology categories. In creating CMEM, over 350 vehicles were extensively tested on a chassis
dynamometer, where second-by-second measurements were made of both engine-out and tailpipe
emissions of carbon monoxide, hydrocarbons, oxides of nitrogen, and carbon dioxide. CMEM itself runs
on a personal computer or on a UNIX workstation. The model and the emissions database are both
available on a CD.

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Prepared for: National Cooperative Highway Research Program Transportation Research Board National Research Council


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