Opportunities for Reducing Emissions from Vehicle Idling and Customs Processing at the US-Mexico Border

Border crossings between Mexico and the United States generate significant amounts of air pollution, which can pose health threats to personnel at the ports of entry (POEs) as well as local communities. Using the Mariposa POE in Nogales, Arizona as a case study, light-duty and heavy-duty vehicle emissions are analyzed with the objective of identifying emission reduction strategies including information technology, inspection processes and physical infrastructure improvements, and fuel switching. Historical traffic information as well as field data were used to establish a simulation model of vehicle movement in VISSIM. Four simulation scenarios with varied congestion levels were considered to represent real-world seasonal changes in traffic volume. The VISSIM output was analyzed using the EPA’s MOVES emission simulation software for six major air pollutants. For the highest congestion scenario total emissions increase by as much as 178% for PM₂.₅ and NOₓ, and 187% for CO, SO₂, GHGs, and NMHC over uncongested conditions for a two-hour period. POE emissions could be reduced through streamlined POE operations, incentivizing fuel mix upgrades, switching fuel types, encouraging vehicle turnover, and rapid adoption of modern emission control devices. Combinations of these strategies could reduce pollutants by as much as 96% for PM₂.₅, 91% for NOₓ, 89% for CO, SO₂, 65% for GHGs, 94% for NMHC, and completely eliminate SO₂. These changes would not only reduce emissions at the POE, but would have air-quality benefits for nearby populations in both the US and Mexico.