Geographic Information System Framework for Modeling Mobile-Source Emissions

Abstract

Because vehicle activities and the emissions associated with them can be correlated with specific points in time and space, the modeling capabilities of a geographic information system (GIS) are well suited to the modeling of mobile-source emissions. A GIS-based modeling approach can provide emissions estimates for both on-network and off-network vehicle activities on a modal basis (as a function of various vehicle operating modes that significantly affect vehicle emission rates). An entire metropolitan region can be modeled on a zone, link, and point basis. Vehicle subfleet composition can be tracked or estimated and combined with estimates of vehicle activity and characteristic operating modes to provide emissions estimates in a spatial and temporal context. Emissions from various modal activities are aggregated into grid cells to be used as input to an airshed model. Identifying spatial and temporal distributions of these activities adds to a greater understanding of emissions impacts. A research prototype of this modeling concept was produced to illustrate its capabilities and identify difficulties that must be addressed in the development of a fully functional model. The GIS-based displays and hard-copy maps that present the spatial variability of emissions levels help improve the communication of research findings to decision makers and the public. The effort being undertaken at Georgia Institute of Technology in conjunction with the Environmental Protection Agency to develop a next-generation modal emissions model within a GIS framework is described.