Sample Frame Creation
Creating a suitable sampling frame for nationally representative observational transportation studies is challenging without nationally consistent sources of VMT or AADT for all road types. U.S. Census Bureau’s Topologically Integrated Geographic Encoding and Referencing (TIGER) is a suitable frame due to its complete coverage. U.S. TIGER is not a transportation study frame, and its primary purpose is a framework for Census data collection. However, their TIGER/Line products provide a common geospatial framework for use in linking statistical and other data in GIS. While not perfect, TIGER line files have provided superior coverage for our observational studies, and we improved their road type classifications using other data sources.