http://www.rita.dot.gov/bts/data_and_statistics/intermodal_transportation_database.html

The Intermodal Transportation Database includes information on the volumes of freight and passenger movement by mode, origin, and destinations; location and connectivity of transportation facilities; and a national accounting of expenditures and capital stocks on each mode of transportation and intermodal combination.

• Volumes of freight movement are collected in the Commodity Flow Survey, the Transborder Freight Data Program, and other sources. Freight movement is also compiled in the Freight Analysis Framework.
• Volumes of passenger movement are collected through the National Household  Travel Survey, airline origins and destinations from a sample of tickets, and the American Travel Survey.
• Location and connectivity of transportation facilities are highlighted by the Intermodal Passenger Connectivity Database.
• Transportation expenditures and capital stocks are highlighted in National Transportation Statistics publication.