Diesel emissions from freight are a key threat to public health. By considering fleet turnover, climate policy, and technology evolution, this study examined the air quality and public health impacts of projected freight emissions in 2050 over the continental United States. Using a WRFSMOKE- CMAQ-BenMAP modeling framework, we quantified the impacts of diesel fine particulate matter (PM2.5) emissions change on air quality, health, and economic benefits. With a projected business-as-usual socioeconomic growth and fleet turnover in freight, simulated PM2.5 concentrations have widespread reductions, between 1-1.5 μg m-3.