Development of a National Transportation Inventory for Air Quality Forecasting

Vehicle emissions of carbon dioxide and co-emitted air pollutants, including nitrogen oxides and carbon monoxide, have significant effects on human health and global climate change. Approximately 30% of CO₂ emissions can be traced to the transportation sector, making this a primary focus for climate adaptation and mitigation. This project involves the creation of a new spatially- and temporally-resolved vehicle emissions inventory using public fuel sales and traffic count data. A novel feature of this work is the creation of a fuel-based inventory, which can be used as input to atmospheric models from urban to continental scales. Since gasoline and diesel-fueled vehicles emit different proportions of compounds of concern, separate fuel sales data were used to calculate emission estimates. The resulting maps, with annual emission estimates resolved to a 4-kilometer grid, were scalable to prior decades (1960-2010) using earlier data. Incorporating data on migration patterns and land use changes allowed us to assess the evolution of traffic emissions in various regions across the country. The results were compared to the EPA’s 2011 National Emission Inventory, which is currently used to guide air quality management efforts. The fuel based inventory stretches back further in time than the NEI, and it benefits from a consistent methodology. Further, the differences between the two help provide a broader understanding of the impact of fossil fuel combustion in the United States.