Characterizing Mobile Emissions by on-board Measurements

This paper presents a “bottom-up” characterization of emissions from mobile sources. It focuses on gridded models that rely on data collected by on-board measuring systems. In order to handle the data and to construct the emission model, a new concept is proposed that consists in assigning proper “emissivity” factors to roadways. These factors consider road transport emissions not only as a consequence of vehicles alone, but also, to some extent, of the road segment itself. Within bottom-up models, the on-road measurement is probably the most realistic approach, particularly when compared to the classical dynamometer testing, because the vehicle is measured as it travels in a given roadway. However the principal drawback is the difficulty to handle the data gathered by the measurements and to properly incorporate it to an emission model. As the roads are here characterized as emitters, a robust description of the distribution of emissions at a spatial and temporal level is possible, contributing to obtain more accurate representations of ambient conditions at a micro scale, its temporal variability and compliance to air quality standards. This paper presents a discussion of the experimental results in the city of Mendoza, Argentina, as well as a general methodology to derive gridded emission models for mobile sources using the concepts previously introduced.