The effects of exhaust emissions on public welfare have prompted the US Environmental Protection Agency to take various actions toward understanding, modeling, and reducing vehicle air pollution. This study was conducted to better understand the operations and exhaust emissions of heavy-duty diesel-powered tractor-trailer trucks operating in drayage service, which involves the moving of shipping containers to or from port terminals. The study involved combining data regarding drayage operational and exhaust emissions from multiple sources. The first source was emissions and activity data collected by portable emissions measurement systems (PEMS) installed on a sample of in-use drayage trucks. PEMS systems measured information such as gaseous- and particulate-matter emission rates, vehicle speed, engine operation data and vehicle location data. The second data source was port terminal gate entry/exit logs for all drayage trucks entering the two Port of Houston Authority container terminals, cross-referenced with state registration data for vehicle information. The datasets were combined to analyze model year characteristics of drayage trucks over time, evaluate port visit frequencies and durations, and assess geographic distributions of trucks that operate in port service. Specific operational characteristics were evaluated and overall pollutant emission masses were estimated for comparison within and outside of port terminals. The findings of this work indicate that less than 3.5 percent of gaseous drayage truck emissions are released during operation within port terminals. Drayage trucks tend to be older than typical class 8 tractors and this contributes to higher in-use emissions rates than the wider fleet of heavy-duty trucks.