The Transportation Services Index (TSI), produced by the U.S. Department of Transportation (DOT), Bureau of Transportation Statistics (BTS), measures the movement of freight and passengers. The index combines seasonally adjusted data on freight and passenger travel, which have been weighted to yield a monthly measure of transportation services output. The TSI is represented by three indexes: freight transportation services (freight TSI), passenger transportation services (passenger TSI), and total TSI (freight and passenger combined). The TSI freight index combines air revenue ton-miles, rail carloads, rail intermodal traffic, truck tonnage, tonnage carried on U.S. internal waterways, petroleum pipeline movement, and natural gas consumption. The TSI passenger index combines air revenue passenger miles, rail passenger miles, and public transit ridership.

The TSI includes only domestic “for-hire” transportation operated on behalf of or by a company that provides freight or passenger transport services to external customers for a fee. Not included in the for-hire population is taxi and intercity bus services; in-house transportation, which includes vehicles owned by private firms providing services to that firm; by private firms providing services to that firm; in the family car). The for-hire transportation services component constitutes approximately 60 percent of total transportation services [USDOT BTS TSA 2015].