Abstract
The U.S. Environmental Protection Agency's MOBILE emission rate model is used to evaluate carbon monoxide, hydrocarbon, nitrogen oxide, and particulate matter impacts of major transportation projects. Using fleet characteristics, environmental conditions, and on-road operating conditions, MOBILE estimates fleet average emission rates. Coupling projected traffic volumes and physical roadway characteristics yields pollutant mass flux rates with which dispersion models predict downwind pollutant concentrations. Distance-flux relationships may also prove useful in pollutant exposure modeling to help quantify relative environmental risks of living or working near major roadways. Applying the MOBILE model requires the creation and execution of scenario-specific input files, which must be properly structured. Researchers developed the MOBILE-matrix model to facilitate more readily the use of MOBILE emission rates in transportation modeling. The matrix creates large emission rate lookup tables that can be applied to traffic in any facility or subregion. It performs all necessary model runs well before a future modeling need. The goal of this specific application is to integrate MOBILE-matrix capabilities into the multimodal transportation planning tool (MTPT) employed by the Georgia Department of Transportation so that it can be used to estimate emissions from rural road facilities throughout the state. Thousands of MOBILE6.2 runs were executed to generate database output files, which were post-processed to create MOBILE-matrix lookup tables for 159 Georgia counties. For each transportation link in the MTPT, emission rates are extracted from the lookup matrix by facility type, average speed, temperature, and so forth. The predicted emissions can then be used for a variety of transportation planning purposes.
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