Impacts of On‐Road Vehicular Emissions on U.S. Air Quality: A Comparison of Two Mobile Emission Models (MOVES and FIVE)

Abstract On‐road vehicles are significant contributors to air pollution globally, particularly to nitrogen oxides (NO x ) and ozone (O 3 ). Quantifying their contribution to air quality is crucial to understanding the trends of vehicle emissions as low‐ and “zero” emission vehicles join the fleet. Modeling on‐road emissions is complex due to various factors like fleet activities, traffic patterns, and meteorological conditions. We compare on‐road emissions from two mobile models: the National Oceanic and Atmospheric Administration Fuel‐based Inventory of Vehicle Emission (FIVE) and the US Environmental Protection Agency Motor Vehicle Emission Simulator (MOVES), finding they contribute 4%–33% to volatile organic compounds (VOCs), NO x , and fine particulate matter (PM 2.5 ) in the contiguous United States (CONUS). Using a regional chemical transport model, we assess air quality effects under different emission scenarios. Both emission data sets yield satisfactory performance, with MOVES showing lower biases in ozone (O 3 ) and PM 2.5 over CONUS, while FIVE performs better at city scales due to higher urban NO x emissions. In January, on‐road emissions increased surface O 3 over western and southern US by up to 9.1%–13.1% but decreased by 2.5% over the northeastern US, while PM 2.5 predictions vary across the US (−85% to 24%). In July, on‐road emissions elevate O 3 and PM 2.5 concentrations by 15%–20% across CONUS, except in some west coast cities. They also greatly contribute to nitrogen dioxide (NO 2 ) by more than 80% near roads and in urban areas. This study highlights the significant impact of on‐road emissions on urban air quality and provides insights for improving air quality forecasting and management.