A government-industry research collaborative asked STI to assess what was known about near-road NO2 concentrations. The study was motivated by the U.S. EPA’s NO2 National Ambient Air Quality Standards (NAAQS) and requirements for regions to measure NO2 within 50 meters of major roads. STI helped these government-industry sponsors evaluate NO2 baseline conditions by analyzing year-long near-road NO2 concentration data sets—one collected in Nevada, another in California. The study findings provided air quality stakeholders with a better understanding of the the importance of near-roadway monitoring and the degree to which near-road air pollution concentrations approach or exceed the NAAQS.