The websites are listed in alphabetical order:
American Public Transportation Association (APTA)
Association of Public Data Users (APDU)
Census Data for Transportation Planning
Center for Environmental Excellence by AASHTO
Center for Urban Transportation Research
Federal Transit Administration
Florida Department of Transportation GIS
FDOT TDM in Florida, Commuter Services
General Transit Feed Specification
Geospatial One Stop: geodata.gov
GIS in Transportation-Planning, Environment, & Realty (U.S. DOT/FHWA)
NASA GIS/Geography Related websites
U.S. Census Bureau: American Community Survey
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