Estimation of Motor Vehicle Emission Factors From Road Measurements of Pollutant Concentrations

Abstract

Motor vehicle emission factors for application in traffic/transport models are often estimated indirectly, through measurements of pollutant concentrations in the close vicinity of a road link. Such an approach provides insight into total vehicle fleet emissions on the link. However, estimation of emission factors form the measured concentration raise a set of complex issues. The concentrations dement not only on the emission factors, but also to a large degree on meteorological factors as well as on the topography of the land. Using the number/mass balance mode, a theoretical relationship was developed that allows for calculation of emission factors from the concentrations measured at a specific point above the road, taking into account wind is the only removal mechanism of the emitted pollutants. By using this model, average emission factors for all vehicles on the road can be estimated and then used to arrive at emission factors for individual types of vehicles, given a known fleet composition. This paper presents an extension of the model to include the effects of humidity and temperature, as well as topographical aspects, on the concentrations measured.